Abstract:Nanpu depression is one of the main oil-producing region in Huanghua depression, oil and gas reservoirs in this depression must be of favorable reservoir forming conditions. This paper applies reservoir anatomy, geochemical data analysis, fault activity periods, source rock hydrocarbon expulsion period, caprock identification and sand and stratum ratio analysis and other measures, uses the reservoir conditions of comprehensive analysis method to study in detail and analyze the source rock, caprock, fracture, reservoir and structural position in 5 aspects in terms of geological condition, we clearly determined hydrocarbon accumulation conditions and their relationship in Nanpu depression. It is considered that there are five favorable geological conditions for oil and gas accumulation in Nanpu depression: ① two source rocks whose thickness is high and the distribution is wide so as to provide adequate oil and gas for migration and accumulation; ②two source rocks provide transporting pathways for oil and gas to migrate; ③three regional caprocks provide sealing for oil and gas to accumulate; ④strata with high ratio between sand stone and stratum so as to provide reservoir space for oil and gas to accumulate; ⑤positive structures near faults connected source rock so as to provide favorable places for oil and gas to accumulate. Through the study of this paper, it will be enriched hydrocarbon accumulation in Nanpu depression, and provides a new thought for next exploration of oil and gas. The result of this study offers important significance to guide the oil-gas exploration in depression basin.

Abstract:The Tarim basin of neotectonic movement is very intensive, which plays an important role in the structural deformation of basin and hydrocarbon accumulation. The period activity by the Orogenic belt from platform margin to stage basin area decreased. From three aspects of fault, fold and drilling induced fractures, this paper mainly analyzes the maximum principal stress direction. The conclusions are the followings:①Kuche, Kalpin and southwest Tarim are forced by extrusion stress function, form the fault zone and fold belt which is distributed in line. With the direction to basin, the formation age gradually becomes variable young, and the stress function gradually becomes weak. The fault strike of Bachu-Maigaiti area is similarly distributed, which are rows of distribution and the same fault strike; The southeast Tarim in the mainly is forced by the strike-slip and squeezed function, and the development of the fault and tectonic belt is parallel distributed; The central Tarim area is mainly forced by strike-slip fault, extrusion function. The torsional stress makes the fold development symmetry by two-way control of fault, and forms the present structural forms. ②The greatest principal stress direction in different blocks of Tarim basin is diverse. In central Tarim area, Kalpin fault uplift and southeast Tarim,the principal stress direction is mainly north-west. The one in southwest Tarim is east-north, and in the Bachu-Maigaiti area is north-east, and in the central Tarim basin, the principal stress direction of this block is north east to north-east. ③The basin neotectonic movement which developed the fault zone and fold belt and its principal stress direction is in accordance with each other, and the main stress direction is of inheritance in time and spatial domain.

Abstract:The Tarim basin of neotectonic movement is very intensive, which plays an important role in the structural deformation of basin and hydrocarbon accumulation. The period activity by the Orogenic belt from platform margin to stage basin area decreased. From three aspects of fault, fold and drilling induced fractures, this paper mainly analyzes the maximum principal stress direction. The conclusions are the followings:①Kuche, Kalpin and southwest Tarim are forced by extrusion stress function, form the fault zone and fold belt which is distributed in line. With the direction to basin, the formation age gradually becomes variable young, and the stress function gradually becomes weak. The fault strike of Bachu-Maigaiti area is similarly distributed, which are rows of distribution and the same fault strike; The southeast Tarim in the mainly is forced by the strike-slip and squeezed function, and the development of the fault and tectonic belt is parallel distributed; The central Tarim area is mainly forced by strike-slip fault, extrusion function. The torsional stress makes the fold development symmetry by two-way control of fault, and forms the present structural forms. ②The greatest principal stress direction in different blocks of Tarim basin is diverse. In central Tarim area, Kalpin fault uplift and southeast Tarim,the principal stress direction is mainly north-west. The one in southwest Tarim is east-north, and in the Bachu-Maigaiti area is north-east, and in the central Tarim basin, the principal stress direction of this block is north east to north-east. ③The basin neotectonic movement which developed the fault zone and fold belt and its principal stress direction is in accordance with each other, and the main stress direction is of inheritance in time and spatial domain.

Abstract:In oil-rich Yongan area, the faults have not only controlled the forming of structure belt, but also played an important role in hydrocarbon migration and accumulation. Based on abundant seismic data and lithology materials, this paper analyzed the feature of major faults. In addition, by combining with fault activity rate analysis and fuzzy comprehensive sealing evaluation in different places of the main faults, the transporting capacity of the main faults in different places is analyzed and the hydrocarbon accumulation regularity is summarized. The results show that east section of Yong3 fault and Yong41 fault, whose activity matches well with the hydrocarbon generation and expulsion periods, but the good sealing property is against the migration of hydrocarbon. The west section of Yong3 fault and Yong41 fault, Yong67 fault which have long active time and match well with the hydrocarbon generation and expulsion periods,and the sealing is poor and making hydrocarbon migration possible, so it is the key regions of reservoir formation. Besides, the three parallel aligned main faults make the reservoir formed in step in the study area, and making the hydrocarbon distribution become shallow gradually from south to north.

Abstract:In oil-rich Yongan area, the faults have not only controlled the forming of structure belt, but also played an important role in hydrocarbon migration and accumulation. Based on abundant seismic data and lithology materials, this paper analyzed the feature of major faults. In addition, by combining with fault activity rate analysis and fuzzy comprehensive sealing evaluation in different places of the main faults, the transporting capacity of the main faults in different places is analyzed and the hydrocarbon accumulation regularity is summarized. The results show that east section of Yong3 fault and Yong41 fault, whose activity matches well with the hydrocarbon generation and expulsion periods, but the good sealing property is against the migration of hydrocarbon. The west section of Yong3 fault and Yong41 fault, Yong67 fault which have long active time and match well with the hydrocarbon generation and expulsion periods,and the sealing is poor and making hydrocarbon migration possible, so it is the key regions of reservoir formation. Besides, the three parallel aligned main faults make the reservoir formed in step in the study area, and making the hydrocarbon distribution become shallow gradually from south to north.

Abstract:The thick reservoir in China is in high water cut stage, and is flooded seriously now, in which the remaining oil is greatly dispersed accordingly. In order to clarify the distribution and influence factors of remaining oil in thick reservoir of point bar in meandering river deposit, and based on the internal configuration analysis of point bar, a fine geological model of point bar is constructed, then,the study on point bar reservoir is carried out by means of numerical simulation method and orthogonal experiment with single factor experiments. The results show that, the remaining oil is mainly distributed in the top of point bar, where the lateral accretion sandwich is blocked and the area between the wells where is not flooded; the remaining oil is overall dispersed and locally enriched. The dip, horizontal spacing, connectivity and curvature of the lateral accretion sandwich, water injection mode and well pattern will all have important impact on the distribution of remaining oil. The dip is smaller, the connectivity is poorer, and the horizontal spacing is greater, the development performance of the meandering river point bar reservoir is better. This paper has an important significance on further research of remaining oil distribution and potential tapping measures.

Abstract:The thick reservoir in China is in high water cut stage, and is flooded seriously now, in which the remaining oil is greatly dispersed accordingly. In order to clarify the distribution and influence factors of remaining oil in thick reservoir of point bar in meandering river deposit, and based on the internal configuration analysis of point bar, a fine geological model of point bar is constructed, then,the study on point bar reservoir is carried out by means of numerical simulation method and orthogonal experiment with single factor experiments. The results show that, the remaining oil is mainly distributed in the top of point bar, where the lateral accretion sandwich is blocked and the area between the wells where is not flooded; the remaining oil is overall dispersed and locally enriched. The dip, horizontal spacing, connectivity and curvature of the lateral accretion sandwich, water injection mode and well pattern will all have important impact on the distribution of remaining oil. The dip is smaller, the connectivity is poorer, and the horizontal spacing is greater, the development performance of the meandering river point bar reservoir is better. This paper has an important significance on further research of remaining oil distribution and potential tapping measures.

Abstract:Aiming at the two levels of fluvial reservoir research and their advantages and disadvantages, this paper points out that the key to the fluvial reservoir research is the recognition and distribution of abandoned channels. There are two main problems existing in the abandoned channels research, one is the uncertainty of abandoned channels recognition, the other is the appearance of abandoned channels that is not always indicated the boundary of a single point bar. So, taking the typical meandering river reservoir architecture research of the upper member of Guantao formation in Gudao oilfield as an example, we put forward four models about the planar distribution of abandoned channels mainly according to the abandoned period of a channel during a single sand layer′s deposition, such as the complex point bar interior type, the main channel peripheral type, cling to meandering belt′s convex bank type and the isolated type. The four types usually appear orderly from below in a sand group which represents the water-transgression in a fluvial depositional system. So, the planar distribution of abandoned channels in different sedimentary period as well as the well log analysis under the dense well pattern has important significance on enhancing the fluvial reservoir architecture research and the development effects.

Abstract:Aiming at the two levels of fluvial reservoir research and their advantages and disadvantages, this paper points out that the key to the fluvial reservoir research is the recognition and distribution of abandoned channels. There are two main problems existing in the abandoned channels research, one is the uncertainty of abandoned channels recognition, the other is the appearance of abandoned channels that is not always indicated the boundary of a single point bar. So, taking the typical meandering river reservoir architecture research of the upper member of Guantao formation in Gudao oilfield as an example, we put forward four models about the planar distribution of abandoned channels mainly according to the abandoned period of a channel during a single sand layer′s deposition, such as the complex point bar interior type, the main channel peripheral type, cling to meandering belt′s convex bank type and the isolated type. The four types usually appear orderly from below in a sand group which represents the water-transgression in a fluvial depositional system. So, the planar distribution of abandoned channels in different sedimentary period as well as the well log analysis under the dense well pattern has important significance on enhancing the fluvial reservoir architecture research and the development effects.

Abstract:Through the comparative analysis on reservoir sand bodies, transverse and longitudinal water, the He8 water in the north of East-2 of Sulige gasfield is divided into 5 water types which are locally edge (bottom) water of channel sand,“lens”water detained in the low-lying area of channel bottom,“lens”water sealed by tight sandstone,“lens”water formed by“single”sandstone body and residual water of dense layer. By the analysis of characteristics of water profile and plane, it is thought that, most of the water layers and water layers of water in longitudinal direction are single thin layers, while the isolated water is presented in the transverse direction, or the water layer sealed by dense layer; in plane, the water is distributed dispersedly comparatively, without the regional discontinuous water. According to comprehensive analysis, the main factors that controlled the water distribution are studied: the channel sand distribution of each layer is the base of formation water distribution; the regional tectonic has little effect on water distributions which are controlled by local sandstone micro-tectonic in partial isolated water system; and the reservoir heterogeneity leads to the fact that the water in reservoir is always isolated and non-communicating in transverse direction.

Abstract:Through the comparative analysis on reservoir sand bodies, transverse and longitudinal water, the He8 water in the north of East-2 of Sulige gasfield is divided into 5 water types which are locally edge (bottom) water of channel sand,“lens”water detained in the low-lying area of channel bottom,“lens”water sealed by tight sandstone,“lens”water formed by“single”sandstone body and residual water of dense layer. By the analysis of characteristics of water profile and plane, it is thought that, most of the water layers and water layers of water in longitudinal direction are single thin layers, while the isolated water is presented in the transverse direction, or the water layer sealed by dense layer; in plane, the water is distributed dispersedly comparatively, without the regional discontinuous water. According to comprehensive analysis, the main factors that controlled the water distribution are studied: the channel sand distribution of each layer is the base of formation water distribution; the regional tectonic has little effect on water distributions which are controlled by local sandstone micro-tectonic in partial isolated water system; and the reservoir heterogeneity leads to the fact that the water in reservoir is always isolated and non-communicating in transverse direction.

Abstract:The shore-shallow lacustrine beach-bar sandbodies are widely developed during the period of the second member of the Shahejie formation of Paleogene in Chexi sag. The characteristics of grain sizes and their hydrodynamic meaning of beach-bar sandbodies are studied based on the description of cores and other correlated analyses and tests. There mainly occurs four kinds of grain size probability curves, which are low cutoff point-high slope-one bouncing population-one suspension population pattern, high cutoff point-high slope-one bouncing population-one suspension population pattern, two bouncing populations-one suspension population pattern and rolling population-bouncing population-suspension population pattern. Three kinds of grain size-standard deviation diagrams occur. The environmentally sensitive grain size components of beach-bar sandbodies has been studied using the method of grain size-standard deviation combined with the analysis of grain size probability curves, and there are four kinds of environmentally sensitive grain size components that are determined in the study area, which respectively represent suspension transportation, coastal current, wave and flow of distributary channel of delta. The wave and coastal current are the main hydrodynamics of the four kinds of hydrodynamics which control the formation and development of beach-bar sandbodies. The wave is the dominant hydrodynamic that controls the formation and development of beach-bar sandbodies of the second member of Shahejie formation in Chexi sag according to the calculation of the percentage of environmentally sensitive grain size components of wave and coastal current in the grain population.The percentage of wave environmentally sensitive grain size components is generally more than 60%. The effect degree of coastal current and its percentage in the grain population is very low. The percentage of coastal current is generally below 20% in Chexi sag.

Abstract:The shore-shallow lacustrine beach-bar sandbodies are widely developed during the period of the second member of the Shahejie formation of Paleogene in Chexi sag. The characteristics of grain sizes and their hydrodynamic meaning of beach-bar sandbodies are studied based on the description of cores and other correlated analyses and tests. There mainly occurs four kinds of grain size probability curves, which are low cutoff point-high slope-one bouncing population-one suspension population pattern, high cutoff point-high slope-one bouncing population-one suspension population pattern, two bouncing populations-one suspension population pattern and rolling population-bouncing population-suspension population pattern. Three kinds of grain size-standard deviation diagrams occur. The environmentally sensitive grain size components of beach-bar sandbodies has been studied using the method of grain size-standard deviation combined with the analysis of grain size probability curves, and there are four kinds of environmentally sensitive grain size components that are determined in the study area, which respectively represent suspension transportation, coastal current, wave and flow of distributary channel of delta. The wave and coastal current are the main hydrodynamics of the four kinds of hydrodynamics which control the formation and development of beach-bar sandbodies. The wave is the dominant hydrodynamic that controls the formation and development of beach-bar sandbodies of the second member of Shahejie formation in Chexi sag according to the calculation of the percentage of environmentally sensitive grain size components of wave and coastal current in the grain population. The percentage of wave environmentally sensitive grain size components is generally more than 60%. The effect degree of coastal current and its percentage in the grain population is very low. The percentage of coastal current is generally below 20% in Chexi sag.

Abstract:It is proved by practice of exploration that the Shizigou Paleogene reservoir contains abundant hydrocarbon resources, but deep oil-gas exploration didn’t make a big breakthrough, and the major reason is that, a poor understanding of hydrocarbon accumulation stages restrains the accurate research about accumulation process. In this paper, through the microscopic observation, fluorescence analysis and homogenization temperature and salinity test of fluid inclusions in Paleogene reservoirs of study area, the hydrocarbon charging history of Paleogene reservoir have been discussed. The result shows that there are two major stages. By integrating with the study on the burial and thermal history, the first change occurs in middle Pliocene(12-10 Ma bp) and the entrapped fluid inclusions are mainly consisted of liquid hydrocarbon and gas-liquid hydrocarbon with buff-yellow and yellow-green fluorescent light. The second time occurs in the final stage of Pliocene (4-2 Ma bp) and the entrapped fluid inclusions are mainly consisted of gas-liquid hydrocarbon with yellow-green and green fluorescent light. In addition, the reservoirs in study area also have the characteristics of multi-stage charging and continual charging, but major fluid injection time is in the later period on the whole. Therefore, the scale of later hydrocarbon accumulation is larger.

Abstract:It is proved by practice of exploration that the Shizigou Paleogene reservoir contains abundant hydrocarbon resources, but deep oil-gas exploration didn’t make a big breakthrough, and the major reason is that, a poor understanding of hydrocarbon accumulation stages restrains the accurate research about accumulation process. In this paper, through the microscopic observation, fluorescence analysis and homogenization temperature and salinity test of fluid inclusions in Paleogene reservoirs of study area, the hydrocarbon charging history of Paleogene reservoir have been discussed. The result shows that there are two major stages. By integrating with the study on the burial and thermal history, the first change occurs in middle Pliocene(12-10 Ma bp) and the entrapped fluid inclusions are mainly consisted of liquid hydrocarbon and gas-liquid hydrocarbon with buff-yellow and yellow-green fluorescent light. The second time occurs in the final stage of Pliocene (4-2 Ma bp) and the entrapped fluid inclusions are mainly consisted of gas-liquid hydrocarbon with yellow-green and green fluorescent light. In addition, the reservoirs in study area also have the characteristics of multi-stage charging and continual charging, but major fluid injection time is in the later period on the whole. Therefore, the scale of later hydrocarbon accumulation is larger.

Abstract:It is indicated that the deep overpressures exits in the northern of Dongpu depression, the rapid deposition and hydrocarbon generation are the two key control factors which result in diagenetic overpressure and hydrocarbon generation overpressure separately.The diagenetic overpressure is mainly developed in the deep sag area and others in transitional zone. The hydrocarbon generation overpressure is developed in the whole depression except for Huqing area in western fault zone. It is pointed out that the constrain effect on the thermal evolution of organic matter has 4 conditions, which includes threshold overpressure, early developed overpressure, good organic matter type and high original TOC content. The early developed overpressure significantly inhibits the thermal evolution of organics in the north part of Dongpu depression. Based on analysis of threshold value, the distribution and forming period of overpressure,this paper predicts the target zones which are inhibited by deep overpressure in the north part of Dongpu depression.

Abstract:It is indicated that the deep overpressures exits in the northern of Dongpu depression, the rapid deposition and hydrocarbon generation are the two key control factors which result in diagenetic overpressure and hydrocarbon generation overpressure separately.The diagenetic overpressure is mainly developed in the deep sag area and others in transitional zone. The hydrocarbon generation overpressure is developed in the whole depression except for Huqing area in western fault zone. It is pointed out that the constrain effect on the thermal evolution of organic matter has 4 conditions, which includes threshold overpressure, early developed overpressure, good organic matter type and high original TOC content. The early developed overpressure significantly inhibits the thermal evolution of organics in the north part of Dongpu depression. Based on analysis of threshold value, the distribution and forming period of overpressure,this paper predicts the target zones which are inhibited by deep overpressure in the north part of Dongpu depression.

Abstract:The lower Jurassic layer of Yakela fault arch was formed during subsidence. The control on sediment of area tectonism was quite different in various periods and with various depositional features. The study on main Cretaceous reservoirs was very mature. The discovery of new area of oil and gas, and research on the earlier and thinner lower Jurassic layer became increasingly prominent. The four sand beds of target zone displayed typical depositional features. This paper succeeded to specifically elaborate these typical sedimentary features and differences from fragments, single well facies, provenance systems, plane sedimentary facies and longitudinal strata correlation. The sedimentary subfacies of lower Jurassic layer experienced facies from delta front to delta plain of braided river to shallow lake from bottom to top. Three main provenance systems behaved significantly different on supplying patterns and quantities.The Ⅲ-Ⅳsand bed is deposited with channel sandbodies of delta-front and three provenance systems are abundantly supplied. The distribution form of sedimentary facies in plane is in shaped of dumbbell that is represented by SC2 and S4 well area, in accordance with the distribution of effective reservoir. The Ⅱsand bed is swamp deposited as delta-plain and provenances reducing increasingly. TheⅠsand bed transited to shallow lake facies and the provenances was nearly interrupted. The microfacies display obvious differences. The extensive developed and better submarine distributary channel microfacies can be regarded as favorable facies. This paper attributes guides and references not only for subsequent oil/gas potential arguments, but also for researches on characteristics and development of similar oil/gas reservoir.

Abstract:The lower Jurassic layer of Yakela fault arch was formed during subsidence. The control on sediment of area tectonism was quite different in various periods and with various depositional features. The study on main Cretaceous reservoirs was very mature. The discovery of new area of oil and gas, and research on the earlier and thinner lower Jurassic layer became increasingly prominent. The four sand beds of target zone displayed typical depositional features. This paper succeeded to specifically elaborate these typical sedimentary features and differences from fragments, single well facies, provenance systems, plane sedimentary facies and longitudinal strata correlation. The sedimentary subfacies of lower Jurassic layer experienced facies from delta front to delta plain of braided river to shallow lake from bottom to top. Three main provenance systems behaved significantly different on supplying patterns and quantities.The Ⅲ-Ⅳsand bed is deposited with channel sandbodies of delta-front and three provenance systems are abundantly supplied. The distribution form of sedimentary facies in plane is in shaped of dumbbell that is represented by SC2 and S4 well area, in accordance with the distribution of effective reservoir. The Ⅱsand bed is swamp deposited as delta-plain and provenances reducing increasingly.TheⅠsand bed transited to shallow lake facies and the provenances was nearly interrupted. The microfacies display obvious differences. The extensive developed and better submarine distributary channel microfacies can be regarded as favorable facies. This paper attributes guides and references not only for subsequent oil/gas potential arguments, but also for researches on characteristics and development of similar oil/gas reservoir.

Abstract:According to the heterogeneous heavy oil reservoir definition, this paper discusses the reservoir character and classification,and summarizes the unique logging response characters of this reservoir such as upside down oil water location, abnormal oil and water relation. We think that the lithologic trap and abnormal oil-water gravity segregation phenomenon can explain the unique log response characters according to hydrocarbon migration and accumulation theory, then, we put forward new fluid typing method and new inlayer reservoir further classification evaluation method (NIRFCEM), and applied in field examples. This NIRFCEM is newly developed for inlayer lithofacies subdivision, and oil enrichment for logging evaluation. The newly founded NIRFCEM overlay methods for porosity and oil saturation, and effective permeability and movable fluid saturation achieve good geological consistency in practice, which supplies highly accurate logging evaluation results for the development and perforation optimization.

Abstract:According to the heterogeneous heavy oil reservoir definition, this paper discusses the reservoir character and classification,and summarizes the unique logging response characters of this reservoir such as upside down oil water location, abnormal oil and water relation. We think that the lithologic trap and abnormal oil-water gravity segregation phenomenon can explain the unique log response characters according to hydrocarbon migration and accumulation theory, then, we put forward new fluid typing method and new inlayer reservoir further classification evaluation method (NIRFCEM), and applied in field examples. This NIRFCEM is newly developed for inlayer lithofacies subdivision, and oil enrichment for logging evaluation. The newly founded NIRFCEM overlay methods for porosity and oil saturation, and effective permeability and movable fluid saturation achieve good geological consistency in practice, which supplies highly accurate logging evaluation results for the development and perforation optimization.

Abstract:With the improvement degree of exploration and the increasing difficulty of development, we need more geophysical techniques than before. In order to solve the difficulty in prediction of fractured shale reservoirs, we develop a new technique named density projection using the method of modern signal analysis. It can not only display many attributes overlay but also avoid the problem of multi-solution. It can further perfect the technology series of reservoir prediction. The technique has been applied in the lower Es3 of Luojia region of Bonan sag of Shengli oilfield, and obtained a good result. It can guide us to understand the distributing of fractured reservoirs and help us to deploy horizontal wells.

Abstract:With the improvement degree of exploration and the increasing difficulty of development, we need more geophysical techniques than before. In order to solve the difficulty in prediction of fractured shale reservoirs, we develop a new technique named density projection using the method of modern signal analysis. It can not only display many attributes overlay but also avoid the problem of multi-solution. It can further perfect the technology series of reservoir prediction. The technique has been applied in the lower Es3 of Luojia region of Bonan sag of Shengli oilfield, and obtained a good result. It can guide us to understand the distributing of fractured reservoirs and help us to deploy horizontal wells.

Abstract:In order to describe the mechanism and characteristics of enhanced liquid production in heterogeneous reservoirs, and based on the traditional black oil model, a three-dimensional, three-phase mathematical model, which takes threshold pressure gradient into account, is put forward. And, a corresponding numerical simulator is developed, in which the Implicit Pressure Explicit Saturation Method is used. Through establishing the conceptual models, the influences of permeability ratio (the ratio of highest permeability to lowest permeability), the amplitude and time of enhanced liquid production, and the initial liquid production rate are studied. The results show that: under certain amplitude of enhanced liquid production, the development effect of enhanced liquid production becomes worse with the increase of permeability ratio. The development effect of enhanced liquid production gets better while the amplitude of enhanced liquid production increases. The earlier of enhanced liquid production, the better development effect is. When the initial liquid production rate is larger, the development effect of enhanced liquid production for the model with larger permeability ratio is better.

Abstract:In order to describe the mechanism and characteristics of enhanced liquid production in heterogeneous reservoirs, and based on the traditional black oil model, a three-dimensional, three-phase mathematical model, which takes threshold pressure gradient into account, is put forward. And, a corresponding numerical simulator is developed, in which the Implicit Pressure Explicit Saturation Method is used. Through establishing the conceptual models, the influences of permeability ratio (the ratio of highest permeability to lowest permeability), the amplitude and time of enhanced liquid production, and the initial liquid production rate are studied. The results show that: under certain amplitude of enhanced liquid production, the development effect of enhanced liquid production becomes worse with the increase of permeability ratio. The development effect of enhanced liquid production gets better while the amplitude of enhanced liquid production increases. The earlier of enhanced liquid production, the better development effect is. When the initial liquid production rate is larger, the development effect of enhanced liquid production for the model with larger permeability ratio is better.

Abstract:Most of the fracture prediction methods are based on the present geological structure characteristics, without considering the effect of multi-stage tectonic movements, especially the effects of the fault shape on strata in hanging wall. Using the Plane Model in 3DMove software, the method based on 3D restoration is applied to calculate the present accumulative strain and predict fractures, in the middle E2s3 intrusive rocks of Shang541 region, Huimin sag. The principal curvature of the top of intrusive rocks is also calculated.With reference to the porosity and permeability data of two wells, the fracture prediction result by 3D restoration is contrasted with that by curvature method. It shows that the 3D restoration method is highly applicable to the fracture prediction in special lithologic body,such as intrusive rocks, of which the curved surface is not formed totally by tectonic deformation.

Abstract:The economic and reasonable well pattern density is the key point to enhance the reservoir conformance factor and ultimate recovery factor, and the oilfield development adjustment is also based on it. In view of the problem that the result of well pattern density made by Cher card Geoff formula cannot be suitable for the actual situation of production, we formulate the economic well pattern density from the theory and practical method so as to clarify and definite the connotation and extension of current common well pattern density, and define the conception of economic well pattern density. Based on the improvement of Cher card Geoff formula, we found the empirical formula, that calculates the economic limit well pattern density, can be suitable for various different kinds of oil blocks and reservoir in Sinopec. According to the statistical data of practical reserves abundance and fluidity in different type reservoir, we combine the state with the rectified Cher card Geoff formula, and use this formula to calculate the economic limit well pattern density of different type reservoir in five primary oil blocks, which include the high permeability reservoir, low permeability reservoir, and heavy oil reservoir. The result of calculation shows that we can drill the infilling well in the number of 20 515 and 19 466 in eastern main oil block and different types reservoir, when the price of oil can maintain at 80 $/bar.

Abstract:The economic and reasonable well pattern density is the key point to enhance the reservoir conformance factor and ultimate recovery factor, and the oilfield development adjustment is also based on it. In view of the problem that the result of well pattern density made by Cher card Geoff formula cannot be suitable for the actual situation of production, we formulate the economic well pattern density from the theory and practical method so as to clarify and definite the connotation and extension of current common well pattern density, and define the conception of economic well pattern density. Based on the improvement of Cher card Geoff formula, we found the empirical formula, that calculates the economic limit well pattern density, can be suitable for various different kinds of oil blocks and reservoir in Sinopec. According to the statistical data of practical reserves abundance and fluidity in different type reservoir, we combine the state with the rectified Cher card Geoff formula, and use this formula to calculate the economic limit well pattern density of different type reservoir in five primary oil blocks, which include the high permeability reservoir, low permeability reservoir, and heavy oil reservoir. The result of calculation shows that we can drill the infilling well in the number of 20 515 and 19 466 in eastern main oil block and different types reservoir, when the price of oil can maintain at 80 $/bar.

Abstract:Multilateral wells technology is a new technology after the horizontal well. The application of this technology has significant technical and economic advantages because of space limitations of offshore platform for oilfield development. But with continuously increase of multilateral well quantity, it was very important to forecast its productivity precisely to reduce development risk of the oilfield.Basing on green’s function and source function, the potential distribution of arbitrary trajectory well in box shaped closed reservoir was derived using superposition principle and mirror reflection method. The pressure drop model of variable mass flow in wellbore was derived according to conservation of mass and momentum. And, finally the two models above are coupled according to continuity equation to form the productivity prediction model for arbitrary trajectory well. The effects of lateral location, different angles and lateral symmetry on the production of multilateral wells are analyzed using this model. The numerical results indicate that the increasing the angle between laterals and the main wellbore can reduce the interference among them. When the angle is restricted by drilling technology, prolonging the length of each lateral can increase the productivity of the multilateral well. Laterals should be disposed in the heel section of the main wellbore with an asymmetric distribution, which is beneficial to enhancing the productivity of the multilateral well.

Abstract:Multilateral wells technology is a new technology after the horizontal well. The application of this technology has significant technical and economic advantages because of space limitations of offshore platform for oilfield development. But with continuously increase of multilateral well quantity, it was very important to forecast its productivity precisely to reduce development risk of the oilfield.Basing on green’s function and source function, the potential distribution of arbitrary trajectory well in box shaped closed reservoir was derived using superposition principle and mirror reflection method. The pressure drop model of variable mass flow in wellbore was derived according to conservation of mass and momentum. And, finally the two models above are coupled according to continuity equation to form the productivity prediction model for arbitrary trajectory well. The effects of lateral location, different angles and lateral symmetry on the production of multilateral wells are analyzed using this model. The numerical results indicate that the increasing the angle between laterals and the main wellbore can reduce the interference among them. When the angle is restricted by drilling technology, prolonging the length of each lateral can increase the productivity of the multilateral well. Laterals should be disposed in the heel section of the main wellbore with an asymmetric distribution, which is beneficial to enhancing the productivity of the multilateral well.

Abstract:Remaining economic recoverable reserves are based on the gradual change law of production of oil and gas, and it is forecasted and estimated according to SEC criterion. It is closely related with the output and replacement ratio of remaining economic recoverable reserves. However, recently, some misunderstandings exist in respects of two indexes and their mutual relationships, and the management and direction to enterprise is still influenced by these uncertainties. Taking the SEC reserves of Shengli oilfield for reference,and considering the related definition of output and replacement ratio on remaining economic recoverable reserves, influencing factors on general character and personality, and based on the overall idea and field example, the mutual relationship and sensitive difference to influencing factors of the two indexes were analyzed. In the meantime, the gradual change law of replacement ratio was discussed. Research results manifest that: from the annual change law of view, it is inconsistent for the relationship between replacement ratio and output, but it is consistent in respect of its overall gradual change trend. Its influencing factors mainly include SEC remaining economic recoverable reserves and its changes in the same year, output components, economic factors, evaluation conductions and difference of sensitivity etc. Based on this, we form the maco-framework on reserves estimation, which can be used as an important replenishment in analysis system of reserves estimation.

Abstract:Remaining economic recoverable reserves are based on the gradual change law of production of oil and gas, and it is forecasted and estimated according to SEC criterion. It is closely related with the output and replacement ratio of remaining economic recoverable reserves. However, recently, some misunderstandings exist in respects of two indexes and their mutual relationships, and the management and direction to enterprise is still influenced by these uncertainties. Taking the SEC reserves of Shengli oilfield for reference,and considering the related definition of output and replacement ratio on remaining economic recoverable reserves, influencing factors on general character and personality, and based on the overall idea and field example, the mutual relationship and sensitive difference to influencing factors of the two indexes were analyzed. In the meantime, the gradual change law of replacement ratio was discussed. Research results manifest that: from the annual change law of view, it is inconsistent for the relationship between replacement ratio and output, but it is consistent in respect of its overall gradual change trend. Its influencing factors mainly include SEC remaining economic recoverable reserves and its changes in the same year, output components, economic factors, evaluation conductions and difference of sensitivity etc. Based on this, we form the maco-framework on reserves estimation, which can be used as an important replenishment in analysis system of reserves estimation.

Abstract:Simplex gradient algorithm has the shortages of slow computational speed and strong randomness of well controls obtained by algorithm in reservoir injection-production optimization, etc. To solve these problems, a modified simplex gradient algorithm is therefore proposed. By choosing appropriate perturbation variables, the modified simplex gradient is approximately equal to the product of well control covariance matrix and the true gradient. Thus, the correlation between the changes of well controls and the control time steps is considered. In addition, the preconditioned strategy is applied in solving the gradient, which avoids the singular value decomposition and pseudo-inverse computation for large matrix. By adjusting the operating production conditions of oil and water wells in each control steps of reservoir production dynamically, the computational efficiency has been significantly improved, and the control result obtained is smoother, which can be operated in practical production applications easily. Moreover, the economic benefit optimized by modified algorithm increases about 10% more than original simplex gradient algorithm. The results verify the effectiveness and feasibility of the algorithm.

Abstract:Simplex gradient algorithm has the shortages of slow computational speed and strong randomness of well controls obtained by algorithm in reservoir injection-production optimization, etc. To solve these problems, a modified simplex gradient algorithm is therefore proposed. By choosing appropriate perturbation variables, the modified simplex gradient is approximately equal to the product of well control covariance matrix and the true gradient. Thus, the correlation between the changes of well controls and the control time steps is considered. In addition, the preconditioned strategy is applied in solving the gradient, which avoids the singular value decomposition and pseudo-inverse computation for large matrix. By adjusting the operating production conditions of oil and water wells in each control steps of reservoir production dynamically, the computational efficiency has been significantly improved, and the control result obtained is smoother, which can be operated in practical production applications easily. Moreover, the economic benefit optimized by modified algorithm increases about 10% more than original simplex gradient algorithm. The results verify the effectiveness and feasibility of the algorithm.

Abstract:Zhongerzhong Ng5 is a multi-layer heavy oil reservoir in Gudao oilfield. There are two major productive layers, such as Ng53 and Ng54, in Ng5 formation. The commingling production and the steam overlap result in large production difference among oil layers in Ng5 formation. Therefore, the distribution of reservoir properties is more and more disequilibrium after multiround of steam stimulation. In this article, numerical simulation technology was employed to analyze distribution characteristics of reservoir properties,such as remaining oil saturation, remaining oil abundance, reservoir pressure and temperature, in multi-layer heavy oil after mature steam stimulation. The results show that high remaining oil saturation is mainly distributed in an area with less production wells. The remaining oil abundance is related to not only remaining oil saturation, but also effective thickness of reservoirs closely. The area of large remaining oil abundance is located in high position of reservoirs or is far from edge water zone. Until September 2011, the pressure level was only 42.93% and the average temperature rose about 2 ℃ in Ng5 formation. Based on the results of numerical simulation, we can provide a guide for the separate zone steam injection or steam flooding method to enhance oil recovery in multi-layer heavy oil reservoirs.

Abstract:Zhongerzhong Ng5 is a multi-layer heavy oil reservoir in Gudao oilfield. There are two major productive layers, such as Ng53 and Ng54, in Ng5 formation. The commingling production and the steam overlap result in large production difference among oil layers in Ng5 formation. Therefore, the distribution of reservoir properties is more and more disequilibrium after multiround of steam stimulation. In this article, numerical simulation technology was employed to analyze distribution characteristics of reservoir properties,such as remaining oil saturation, remaining oil abundance, reservoir pressure and temperature, in multi-layer heavy oil after mature steam stimulation. The results show that high remaining oil saturation is mainly distributed in an area with less production wells. The remaining oil abundance is related to not only remaining oil saturation, but also effective thickness of reservoirs closely. The area of large remaining oil abundance is located in high position of reservoirs or is far from edge water zone. Until September 2011, the pressure level was only 42.93% and the average temperature rose about 2 ℃ in Ng5 formation. Based on the results of numerical simulation, we can provide a guide for the separate zone steam injection or steam flooding method to enhance oil recovery in multi-layer heavy oil reservoirs.

Abstract:In this paper based on the pseudo stable seepage theory and mathematical model for numerical simulation of water-oil two phase reservoir, and considering the influence of start-up pressure gradient, a inner boundary conditions is derived, in which three cases were considered: fixed flow pressure, fixed oil production rate and fixed liquid production rate. Then, by means of full implicit finite difference scheme, the corresponding numerical model is established and solved by pretreatment conjugate gradient method. The simulation results show that, in inner boundary conditions, the start-up pressure gradient obviously affect flowing pressure of wells. In case of fixed oil production rate, with the increase of start-up pressure gradient, the flowing pressure becomes lower.

Abstract:In this paper based on the pseudo stable seepage theory and mathematical model for numerical simulation of water-oil two phase reservoir, and considering the influence of start-up pressure gradient, a inner boundary conditions is derived, in which three cases were considered: fixed flow pressure, fixed oil production rate and fixed liquid production rate. Then, by means of full implicit finite difference scheme, the corresponding numerical model is established and solved by pretreatment conjugate gradient method. The simulation results show that, in inner boundary conditions, the start-up pressure gradient obviously affect flowing pressure of wells. In case of fixed oil production rate, with the increase of start-up pressure gradient, the flowing pressure becomes lower.

Abstract:The second member of Shuangyang formation in Moliqing fault depression is the main hydrocarbon exploration target in the Yitong basin. Given the low porosity and permeability, we have studied the damage factors of the reservoir in the mining process, and analyzed the susceptibility of the second member of Shuangyang formation which is located in the northwest edge of Moliqing fault depression with the experiments of reservoir flow sensitivity on the basis of understanding the nature of the rock and mineral composition characteristics. The analysis results show that the water sensitivity index of 66.08% on average, with the critical salinity 6 272 mg/L,speed sensitivity index of 37.23% on average, acid sensitivity index of -31.37% on average and the average alkaline sensitivity index of 7.71%. It shows that the reservoir has the strong water sensitivity, moderate-strong salt sensitivity, moderate speed sensitivity, weak alkaline sensitivity and no acid sensitivity. There are many sensitive clay minerals like kaolinite, chlorite, smectite mixed-layer and illite, and the distribution characteristics of these sensitive clay minerals is the most important factor in the mining process. Therefore,when operation is done on the second member of Shuangyang formation of Moliqing oil reservoir, it should prevent speed sensitive and water sensitive firstly. Other sensitive factors should be taken into account to take corresponding measures to protect the reservoir.

Abstract:The second member of Shuangyang formation in Moliqing fault depression is the main hydrocarbon exploration target in the Yitong basin. Given the low porosity and permeability, we have studied the damage factors of the reservoir in the mining process, and analyzed the susceptibility of the second member of Shuangyang formation which is located in the northwest edge of Moliqing fault depression with the experiments of reservoir flow sensitivity on the basis of understanding the nature of the rock and mineral composition characteristics. The analysis results show that the water sensitivity index of 66.08% on average, with the critical salinity 6 272 mg/L,speed sensitivity index of 37.23% on average, acid sensitivity index of -31.37% on average and the average alkaline sensitivity index of 7.71%. It shows that the reservoir has the strong water sensitivity, moderate-strong salt sensitivity, moderate speed sensitivity, weak alkaline sensitivity and no acid sensitivity. There are many sensitive clay minerals like kaolinite, chlorite, smectite mixed-layer and illite, and the distribution characteristics of these sensitive clay minerals is the most important factor in the mining process. Therefore,when operation is done on the second member of Shuangyang formation of Moliqing oil reservoir, it should prevent speed sensitive and water sensitive firstly. Other sensitive factors should be taken into account to take corresponding measures to protect the reservoir.

Abstract:According to the reservoir condition of Shengli oilfield, the new surfactant/polymer binary compound system, microscopic models (core flake) flooding experiments and normal cylindrical core flooding experiments are carried out in the laboratory. Based on the water flooding effect, the flooding effects of surfactant flooding, polymer flooding and SP binary compound system are compared,and focusing on the washing oil capacity and carrying oil capacity of the surfactants, polymers and SP binary compound system in the microcosmic pore and the microscopic seepage properties in the process, and the microscopic mechanism of SP binary compound system are tested thoroughly. The results show that the flooding effect of binary compound system is better than that of polymer or surfactant flooding. In the visualization flooding experiments of the core flake, different flooding sweep efficiency of 3 different solvents result in the different residual oil area in the core flake, and residual oil area of SP binary compound system is the least, while its sweeping efficiency is the highest of the three, and its sweeping efficiency is raised by about 2.59% and 11.8% percentage than polymer flooding and surfactant flooding, respectively. In the normal cylindrical core flooding, the displacement efficiency of SP system flooding is raised by about 1.43% and 20.70% than polymer flooding and surfactant flooding, respectively.

Abstract:According to the reservoir condition of Shengli oilfield, the new surfactant/polymer binary compound system, microscopic models (core flake) flooding experiments and normal cylindrical core flooding experiments are carried out in the laboratory. Based on the water flooding effect, the flooding effects of surfactant flooding, polymer flooding and SP binary compound system are compared,and focusing on the washing oil capacity and carrying oil capacity of the surfactants, polymers and SP binary compound system in the microcosmic pore and the microscopic seepage properties in the process, and the microscopic mechanism of SP binary compound system are tested thoroughly. The results show that the flooding effect of binary compound system is better than that of polymer or surfactant flooding. In the visualization flooding experiments of the core flake, different flooding sweep efficiency of 3 different solvents result in the different residual oil area in the core flake, and residual oil area of SP binary compound system is the least, while its sweeping efficiency is the highest of the three, and its sweeping efficiency is raised by about 2.59% and 11.8% percentage than polymer flooding and surfactant flooding, respectively. In the normal cylindrical core flooding, the displacement efficiency of SP system flooding is raised by about 1.43% and 20.70% than polymer flooding and surfactant flooding, respectively.

Abstract:Steam flooding can enhance greatly the heavy oil recovery. However, for single steam flooding, it is possible to decrease the steam sweep efficiency resulted by poor heavy oil development efficiency due to steam channeling and heterogeneity. This paper has designed an experiment of nitrogen foam-assisted steam flooding and studied the oil displacement efficiency of single steam flooding and foam-assisted steam flooding. The experiment result shows that the oil displacement efficiency of single steam flooding is 63.52%,while the foam-assisted steam flooding is 69.65%, which is higher than that of former. And, it is testified that the nitrogen foam-assisted steam flooding can dramatically improve the oil displacement efficiency. In addition, we have studied the injection parameter optimization of nitrogen foam-assisted steam flooding. The result is that 1:1 of gas-liquid ratio, 0.5% of foam agent concentration and lower water cut of foam injection time. This experiment demonstrates that nitrogen foam-assisted steam flooding can be used in high permeability formation to enhance oil displacement efficient, and obtain good heavy oil reservoir development.

Abstract:The rich resources of tight sandstone reservoir exist in Shengli oilfield, however, it is of the features of deep, fine, thin, poor and scattered distribution. The deployment of vertical wells on low productivity reservoir can only be of the characteristics of early rapid production decline with poor efficiency. In order to improve the level of development of tight sandstone reservoir, the horizontal well technology research and test are implemented through design and operation optimization to enhance the fast drilling technology for horizontal well, and obtain the break through for the tight reservoir productivity. In the field, we formed the horizontal well techniques with multi-stage fracturing by means of perfection of matching fracturing and completion pipes, field injection and storage equipment and fracturing monitoring approaches. Until the end of 2013, the Shengli oilfield has implemented 28 horizontal wells on the tight sandstone reservoir with the success rate of 94.4%, and cumulative production up to 50 746 tons of oil. It provides the reference for the effective development of tight sandstone reservoir in Shengli oilfield.

Abstract:The rich resources of tight sandstone reservoir exist in Shengli oilfield, however, it is of the features of deep, fine, thin, poor and scattered distribution. The deployment of vertical wells on low productivity reservoir can only be of the characteristics of early rapid production decline with poor efficiency. In order to improve the level of development of tight sandstone reservoir, the horizontal well technology research and test are implemented through design and operation optimization to enhance the fast drilling technology for horizontal well, and obtain the break through for the tight reservoir productivity. In the field, we formed the horizontal well techniques with multi-stage fracturing by means of perfection of matching fracturing and completion pipes, field injection and storage equipment and fracturing monitoring approaches. Until the end of 2013, the Shengli oilfield has implemented 28 horizontal wells on the tight sandstone reservoir with the success rate of 94.4%, and cumulative production up to 50 746 tons of oil. It provides the reference for the effective development of tight sandstone reservoir in Shengli oilfield.

Abstract:By means of analysis on the development characteristics of the complex fault block oil reservoir, and based on the characteristics of remaining oil distribution of the fault block oil reservoir and unstable water injection measures adaptability, and considering the successful experience that the unstable water injection can improve the recovery, we put forward a new treatment for developing complex fault block oil reservoir combined with unstable water injection. First of all, in response to the typical triangle block characteristics and remaining oil status, the reservoir is divided into seven areas, and then we use numerical simulation method to study the pressure, saturation and fluid flow velocity variation characteristics of each area, and then adopt two processes. The simulation results show that the section between angles drives the remaining oil to central section, but the angle section itself contributes less. In order to fully perform unstable injection-production with multilayer characteristics of fault block oil reservoir, we design unstable injection-production coupling method to develop residual oil of complex fault block, and further enhance the water driving recovery factor for complex fault block oil reservoir.

Abstract:By means of analysis on the development characteristics of the complex fault block oil reservoir, and based on the characteristics of remaining oil distribution of the fault block oil reservoir and unstable water injection measures adaptability, and considering the successful experience that the unstable water injection can improve the recovery, we put forward a new treatment for developing complex fault block oil reservoir combined with unstable water injection. First of all, in response to the typical triangle block characteristics and remaining oil status, the reservoir is divided into seven areas, and then we use numerical simulation method to study the pressure, saturation and fluid flow velocity variation characteristics of each area, and then adopt two processes. The simulation results show that the section between angles drives the remaining oil to central section, but the angle section itself contributes less. In order to fully perform unstable injection-production with multilayer characteristics of fault block oil reservoir, we design unstable injection-production coupling method to develop residual oil of complex fault block, and further enhance the water driving recovery factor for complex fault block oil reservoir.

Abstract:The Yanchang oilfield is famous for its ultra-low permeability which is the main factor leading to low productivity, water cut rising fast, high capacity diminishing and low recovery. In order to solve these problems, a new agent has been selected through 22 kinds of agent by static de-oiling experiments, and agent interfacial tension experiments, and the salt experiments and core flow experiments, and its affects has been proved in a water injection zone of Wang214 field in Xingzichuan oilfield. The effects is obvious, for the crude oil production has been improved by 40%, and the oil recovery factor has been enhanced by 6.08%, the cumulative oil is 13 555 tons, and the input-output ratio is 1∶5.06. This displacing agent has a broad prospects in ultra-low permeability reservoirs for the features of high removal efficiency of oil, low interfacial tension, calcium salt tolerance performance, good solubility, high oil displacement efficiency and low cost, which can change the reservoir rock wettability, reduce the injecting pressure, enhance oil recovery, improve the production effects, and have a high percentage of input and output.

Abstract:The Yanchang oilfield is famous for its ultra-low permeability which is the main factor leading to low productivity, water cut rising fast, high capacity diminishing and low recovery. In order to solve these problems, a new agent has been selected through 22 kinds of agent by static de-oiling experiments, and agent interfacial tension experiments, and the salt experiments and core flow experiments, and its affects has been proved in a water injection zone of Wang214 field in Xingzichuan oilfield. The effects is obvious, for the crude oil production has been improved by 40%, and the oil recovery factor has been enhanced by 6.08%, the cumulative oil is 13 555 tons, and the input-output ratio is 1∶5.06. This displacing agent has a broad prospects in ultra-low permeability reservoirs for the features of high removal efficiency of oil, low interfacial tension, calcium salt tolerance performance, good solubility, high oil displacement efficiency and low cost, which can change the reservoir rock wettability, reduce the injecting pressure, enhance oil recovery, improve the production effects, and have a high percentage of input and output.

Abstract:SEC reserves reflect the development and marketing potential of an oil company. Different from technical recoverable reserves in China, SEC reserves is more easily affected by oil price, operating cost and well performance. Based on qualitative research of other evaluators, this paper analyzed quantitatively the correlation between SEC reserves and its four main influencing factors (oil price, operation cost, initial rate and decline rate) on the basis of calculation results of typical units in Shengli Oil Company and made relative plate. A simple and feasible method to forecast SEC reserves was found herein and proved to be accurate enough by a real evaluation example.

Abstract:SEC reserves reflect the development and marketing potential of an oil company. Different from technical recoverable reserves in China, SEC reserves is more easily affected by oil price, operating cost and well performance. Based on qualitative research of other evaluators, this paper analyzed quantitatively the correlation between SEC reserves and its four main influencing factors (oil price, operation cost, initial rate and decline rate) on the basis of calculation results of typical units in Shengli Oil Company and made relative plate. A simple and feasible method to forecast SEC reserves was found herein and proved to be accurate enough by a real evaluation example.

Abstract:In the development of low permeability reservoirs, well patterns are placed along favorable orientation. There is such a possibility that fracture orientation will deflect due to reservoir heterogeneity and the fracture is likely to be on the unfavorable orientation,which may bring great risk to the development of oil field if it is improperly designed. In view of this problem, the suitability between well pattern and hydraulic fracture system in low permeability reservoirs is researched. Based on streamline simulation technology, the characteristic of liquid percolation of rhombus inverted nine-spot fracturing well pattern is analyzed. A numerical simulation model of integral fracturing with deflected fracture is established, taking X block as an example. The influence of different fracture parameters on production performance is studied. Results show that when the fracture orientation deflects, the characteristic of percolation field of fracturing well pattern altered obviously, thus the well symmetry element should be reformed according to the distribution of flow streamlines. The influence of fracture of different wells on production performance is distinct. Besides, there exists notable interference between two fractured wells. Increasing the fracture length of wells placed along unfavorable orientation has a little effect on enhancing oil recovery, and therefore it should be limited to a low value. Increasing the fracture length of wells placed along favorable orientation within a certain range has a great effect on enhancing oil recovery, and therefore it should be extended to a relative high value.

Abstract:In the development of low permeability reservoirs, well patterns are placed along favorable orientation. There is such a possibility that fracture orientation will deflect due to reservoir heterogeneity and the fracture is likely to be on the unfavorable orientation,which may bring great risk to the development of oil field if it is improperly designed. In view of this problem, the suitability between well pattern and hydraulic fracture system in low permeability reservoirs is researched. Based on streamline simulation technology, the characteristic of liquid percolation of rhombus inverted nine-spot fracturing well pattern is analyzed. A numerical simulation model of integral fracturing with deflected fracture is established, taking X block as an example. The influence of different fracture parameters on production performance is studied. Results show that when the fracture orientation deflects, the characteristic of percolation field of fracturing well pattern altered obviously, thus the well symmetry element should be reformed according to the distribution of flow streamlines. The influence of fracture of different wells on production performance is distinct. Besides, there exists notable interference between two fractured wells. Increasing the fracture length of wells placed along unfavorable orientation has a little effect on enhancing oil recovery, and therefore it should be limited to a low value. Increasing the fracture length of wells placed along favorable orientation within a certain range has a great effect on enhancing oil recovery, and therefore it should be extended to a relative high value.

Abstract:In carbonate acidizing, the injected acid reacts with the rock to create a high conductivity channel called wormhole in order to improve the damage in near wellbore zone. Different from experimental conditions, the acid flow is radial flow and the formation pressure increases due to fluids being compressed under reservoir condition. Both of them can influence wormhole propagation to a great extent, it is very necessary to study the wormhole propagation under reservoir condition. We use a 2D two-scale continuum model coupled with a compressed zone model to study it. The results show that the wormhole propagation velocity under reservoir condition is slower than that under experimental condition. Under constant pressure condition, the smaller the compressibility coefficient of formation fluid, the slower the propagation velocity of wormhole, and vice versa. Under constant rate condition, the smaller the compressibility coefficient of formation fluid, the slower the inlet pressure declines and the faster the outlet pressure increases, and vice versa. Due to the effect of compressed zone and implementation condition, the wormhole length has a maximal value under reservoir condition. We also develop a skin factor model to study on an example. It is found that both wormhole propagation velocity and skin factor decline velocity under constant rate condition are higher than those under constant pressure condition before wormhole breaks through the damaged zone, but both of them are very close after wormhole breaks through. Note that, the acid injection volume has an optimal value.

Abstract:In carbonate acidizing, the injected acid reacts with the rock to create a high conductivity channel called wormhole in order to improve the damage in near wellbore zone. Different from experimental conditions, the acid flow is radial flow and the formation pressure increases due to fluids being compressed under reservoir condition. Both of them can influence wormhole propagation to a great extent, it is very necessary to study the wormhole propagation under reservoir condition. We use a 2D two-scale continuum model coupled with a compressed zone model to study it. The results show that the wormhole propagation velocity under reservoir condition is slower than that under experimental condition. Under constant pressure condition, the smaller the compressibility coefficient of formation fluid, the slower the propagation velocity of wormhole, and vice versa. Under constant rate condition, the smaller the compressibility coefficient of formation fluid, the slower the inlet pressure declines and the faster the outlet pressure increases, and vice versa. Due to the effect of compressed zone and implementation condition, the wormhole length has a maximal value under reservoir condition. We also develop a skin factor model to study on an example. It is found that both wormhole propagation velocity and skin factor decline velocity under constant rate condition are higher than those under constant pressure condition before wormhole breaks through the damaged zone, but both of them are very close after wormhole breaks through. Note that, the acid injection volume has an optimal value.

Abstract:In view of the unconventional permeability and porosity of the low permeability gas reservoir, fractured horizontal well becomes the essential to achieve satisfactory production. Based on the actual flow of fractured horizontal well, this paper establishes an equivalent well diameter model of the single fracture horizontal well. Then, according to the superposition rule, the paper set up a complete model of multiple fracture horizontal well, and couple the model with the horizontal flow dynamic. After that, this paper gives the iterative algorithm about the model, and programs the model in the C# environment. Finally, this paper confirms the reliability of this model through a practical example, and gives some applications of this model to optimize hydraulic fracturing.

Abstract:In view of the unconventional permeability and porosity of the low permeability gas reservoir, fractured horizontal well becomes the essential to achieve satisfactory production. Based on the actual flow of fractured horizontal well, this paper establishes an equivalent well diameter model of the single fracture horizontal well. Then, according to the superposition rule, the paper set up a complete model of multiple fracture horizontal well, and couple the model with the horizontal flow dynamic. After that, this paper gives the iterative algorithm about the model, and programs the model in the C# environment. Finally, this paper confirms the reliability of this model through a practical example, and gives some applications of this model to optimize hydraulic fracturing.