Volume 21,Issue 1,2014 Table of Contents
2014, 21(1):1-5.
Abstract:
There is great volume oil-gas which possesses abnormal chemical properties and complicated distribution regularity in rift basins where ever existed strong magmatic activities. In order to study distribution regularity of the oil-gas, we analyzed the intrusion and its neighboring hydrocarbon reservoir in the middle-eastern Zhanhua sag by means of cores observation and geochemical analysis,and found that the magma high temperature, high pressure and active chemical properties not only promoted notably the hydrocarbon generation in source rocks, but also caused a lot of cracks and organic pores. Border facies of the intrusion is good reservoir owing to well-developed gas pores, dissolution pores and contraction cracks. The overpressure field caused by the magmatic activities greatly improved the source rocks’adsorption capability on hydrocarbon. Furthermore, the magmatic activities can form many sorts of traps. The magmatic activities can not only promote oil and gas generation, but also control the oil and gas distribution. In the end, we indicate that the controlling of magma on hydrocarbon is dependent on magma activities time, strength, mode, and spatial relationship between magmatite and source rocks and so on.
There is great volume oil-gas which possesses abnormal chemical properties and complicated distribution regularity in rift basins where ever existed strong magmatic activities. In order to study distribution regularity of the oil-gas, we analyzed the intrusion and its neighboring hydrocarbon reservoir in the middle-eastern Zhanhua sag by means of cores observation and geochemical analysis,and found that the magma high temperature, high pressure and active chemical properties not only promoted notably the hydrocarbon generation in source rocks, but also caused a lot of cracks and organic pores. Border facies of the intrusion is good reservoir owing to well-developed gas pores, dissolution pores and contraction cracks. The overpressure field caused by the magmatic activities greatly improved the source rocks’adsorption capability on hydrocarbon. Furthermore, the magmatic activities can form many sorts of traps. The magmatic activities can not only promote oil and gas generation, but also control the oil and gas distribution. In the end, we indicate that the controlling of magma on hydrocarbon is dependent on magma activities time, strength, mode, and spatial relationship between magmatite and source rocks and so on.
2014, 21(1):6-9.
Abstract:
The study on sedimentary facies and sedimentary system are very important parts of the research of reservoir. In this paper,based on the reservoir in the Dainan-Sanduo formation of Zhenwu oilfield with high thickness and long sedimentary history, variable sedimentation type, and on the research of the depositional setting and provenance, we set up 5 kinds of sedimentary facies which are the anastomosed stream, meandering river, delta, fan-delta and abrupt-fan. After the research of the thickness of the reservoir and the rule of the size grade, the characteristic of provenance in the work area is in two directions and with three provenances. The south and north are both the direction of the provenance, and the south provenance has two parts, one is from the southeast, and the other is from southwest. In the sedimentary evolution of the Dainan-Sanduo formation in Zhenwu oilfield, the south and north provenances controlled the variable sedimentary facies and the sedimentary evolution model, and the transformation of the south and north provenances controlled the sedimentary characteristics, so we set up the transformation style sedimentary evolution model of the Zhenwu oilfield, and it supplies the new method for the analysis of the reservoir origin and distribution.
The study on sedimentary facies and sedimentary system are very important parts of the research of reservoir. In this paper,based on the reservoir in the Dainan-Sanduo formation of Zhenwu oilfield with high thickness and long sedimentary history, variable sedimentation type, and on the research of the depositional setting and provenance, we set up 5 kinds of sedimentary facies which are the anastomosed stream, meandering river, delta, fan-delta and abrupt-fan. After the research of the thickness of the reservoir and the rule of the size grade, the characteristic of provenance in the work area is in two directions and with three provenances. The south and north are both the direction of the provenance, and the south provenance has two parts, one is from the southeast, and the other is from southwest. In the sedimentary evolution of the Dainan-Sanduo formation in Zhenwu oilfield, the south and north provenances controlled the variable sedimentary facies and the sedimentary evolution model, and the transformation of the south and north provenances controlled the sedimentary characteristics, so we set up the transformation style sedimentary evolution model of the Zhenwu oilfield, and it supplies the new method for the analysis of the reservoir origin and distribution.
2014, 21(1):10-15.
Abstract:
The characteristics and distribution of salt lake hydrocarbon source rocks from lower submember of 4th member of the Shahejie formation is short of systematic research. Especially, the hydrocarbon potential of halopelite, gypsum mudstone which are widely developed in salt lake, is less understood. In response to these problems, multiple source rock samples of study layer are collected and analyzed. The experimental results confirmed that, the source rocks interbedded with the gypsum or salt are rich in organic matter, and the type of organic matter in source rocks is mainly II1-I, which is of great oil generation potential. The experiments also confirmed the halopelite, gypsum mudstone have certain hydrocarbon potential, and can function as effective hydrocarbon source rocks. Based on the experiment data, the evaluation methods of salt lake source rocks by logging information are established and the distributions of hydrocarbon source rocks are studied. Results show that, the effective source rocks are mainly distributed in Minfeng area, Lijin sag and downthrown of Shengtuo area. The source rocks in these areas have great total thickness, high organic carbon content. Finally, the evolutions of source rocks are analyzed. The source rocks of lower submember of 4th member of Shahejie formation generally experienced a“fast-slow-fast”burial history, and experienced long oil generated period. At present, the source rock generated wet or dry gas due to the thermal effect, and the crude oil in source rocks and ancient reservoirs started to crack and generate gases.
The characteristics and distribution of salt lake hydrocarbon source rocks from lower submember of 4th member of the Shahejie formation is short of systematic research. Especially, the hydrocarbon potential of halopelite, gypsum mudstone which are widely developed in salt lake, is less understood. In response to these problems, multiple source rock samples of study layer are collected and analyzed. The experimental results confirmed that, the source rocks interbedded with the gypsum or salt are rich in organic matter, and the type of organic matter in source rocks is mainly II1-I, which is of great oil generation potential. The experiments also confirmed the halopelite, gypsum mudstone have certain hydrocarbon potential, and can function as effective hydrocarbon source rocks. Based on the experiment data, the evaluation methods of salt lake source rocks by logging information are established and the distributions of hydrocarbon source rocks are studied. Results show that, the effective source rocks are mainly distributed in Minfeng area, Lijin sag and downthrown of Shengtuo area. The source rocks in these areas have great total thickness, high organic carbon content. Finally, the evolutions of source rocks are analyzed. The source rocks of lower submember of 4th member of Shahejie formation generally experienced a“fast-slow-fast”burial history, and experienced long oil generated period. At present, the source rock generated wet or dry gas due to the thermal effect, and the crude oil in source rocks and ancient reservoirs started to crack and generate gases.
2014, 21(1):16-19.
Abstract:
Selecting modern beach in the Xiashan reservoir as the research object, the sediments, sedimentary structures, grain size characteristics, sedimentary units and sequence of the beach have been studied herein. The sediments of the beach are dominated by better sorted fine sand and silt, and distributed on the shoreland of the reservoir as a sheet. The sedimentary structures are characterized by bedding, ripple, dwelling burrow, shell fragment, and plant debris. The grain-size accumulation curve includes three types,which are two-segment type, two saltation sub-populations, that is, one suspended sub-population type and transition section between one saltation sub-populations and one suspended sub-population type. The sedimentary units are composed of sheet sand of the back beach, beach ridge and space between beach ridges. In the vertical, the beach shows obvious inverted sequence, and develops the shore lake muddy sediments, space between beach ridges, beach ridge and sheet sand of the back beach from the bottom to the top. And, the wind and geomorphology are the important factors controlling the formation of the beach in this area. The study on characteristics and controlling factors of modern beach has an important significance for the hydrocarbon exploration of the beach-bar sandbodies. The distribution area of the beach can be forecasted by analyzing the controlling factors, and the beach sandbody with poor physical property and bar sandbody with better physical property can be identified by studying the characteristics of the beach and the bar.
Selecting modern beach in the Xiashan reservoir as the research object, the sediments, sedimentary structures, grain size characteristics, sedimentary units and sequence of the beach have been studied herein. The sediments of the beach are dominated by better sorted fine sand and silt, and distributed on the shoreland of the reservoir as a sheet. The sedimentary structures are characterized by bedding, ripple, dwelling burrow, shell fragment, and plant debris. The grain-size accumulation curve includes three types,which are two-segment type, two saltation sub-populations, that is, one suspended sub-population type and transition section between one saltation sub-populations and one suspended sub-population type. The sedimentary units are composed of sheet sand of the back beach, beach ridge and space between beach ridges. In the vertical, the beach shows obvious inverted sequence, and develops the shore lake muddy sediments, space between beach ridges, beach ridge and sheet sand of the back beach from the bottom to the top. And, the wind and geomorphology are the important factors controlling the formation of the beach in this area. The study on characteristics and controlling factors of modern beach has an important significance for the hydrocarbon exploration of the beach-bar sandbodies. The distribution area of the beach can be forecasted by analyzing the controlling factors, and the beach sandbody with poor physical property and bar sandbody with better physical property can be identified by studying the characteristics of the beach and the bar.
2014, 21(1):20-23.
Abstract:
There are 9 obvious characteristics of delta progradation units developed in the middle part of 3rd member of Shahejie formation in Dongying depression, and the Dongying delta is shaped in wedge-S type and gradually prograded into the center of the depression, and the feature of progradation stage is remarkable. Based on abundant drilling data and high precision 3D seismic data, this study used a special method in this area to recover the paleo-geomorphology with quantification and high precision shoreline trajectory method, aiming at reconstructing the paleogeomorphology of the nine delta progradation units and revealing the controlling on sedimentation. The results show that, the overall paleogeomorphology characteristics of the middle part of 3rd member of Shahejie formation is gentle south and steep north, and the slope migrates westwards. Distribution and depositional style of sedimentary deposit are coupled well with paleogeomorphology: the delta deposit is mainly prograded gradually along the eastern and southeastern uplifts until the basin, which is affected by the source supply capacity and paleogeomorphology, the delta lobe extends westward along the slope; while in the deep depression area, the sedimentary facies is mainly consisted of semi-deep and deep lacustrine deposits. The sediment in the steeper slope front is prone to be instable and thus forming the turbidite sand body.
There are 9 obvious characteristics of delta progradation units developed in the middle part of 3rd member of Shahejie formation in Dongying depression, and the Dongying delta is shaped in wedge-S type and gradually prograded into the center of the depression, and the feature of progradation stage is remarkable. Based on abundant drilling data and high precision 3D seismic data, this study used a special method in this area to recover the paleo-geomorphology with quantification and high precision shoreline trajectory method, aiming at reconstructing the paleogeomorphology of the nine delta progradation units and revealing the controlling on sedimentation. The results show that, the overall paleogeomorphology characteristics of the middle part of 3rd member of Shahejie formation is gentle south and steep north, and the slope migrates westwards. Distribution and depositional style of sedimentary deposit are coupled well with paleogeomorphology: the delta deposit is mainly prograded gradually along the eastern and southeastern uplifts until the basin, which is affected by the source supply capacity and paleogeomorphology, the delta lobe extends westward along the slope; while in the deep depression area, the sedimentary facies is mainly consisted of semi-deep and deep lacustrine deposits. The sediment in the steeper slope front is prone to be instable and thus forming the turbidite sand body.
2014, 21(1):24-27.
Abstract:
Shale brittleness is one of the most important evaluation factors in shale oil and gas exploration and development. For shale brittleness, the rock mechanics experiment is the main way at present，however, in this paper, we developed a new method of X-ray element logging technique to evaluate in element level. Based on the element composition and correlation between element and mineral, it is revealed that the Si, Ca, Mg element can reflect the content of quartz, calcite and dolomite respectively, which establishes the theory of evaluating shale brittleness by means of X-ray element logging. By means of appropriate method to calculate the silica index, carbonate index and brittleness index to reflect the content of rigidity mineral, we can realize the shale brittleness evaluation while drilling. In accordance with the shale petrology of Shengli oilfield and shale brittleness evaluation standards, the carbonate index is selected to evaluate the shale brittleness so as to establish the four class criterion(CI ≥0.6，high；0.4≤CI＜0.6，medium；0.2≤CI＜0.4，lower；CI＜0.2，low）. After application of this technique in well NY1 and L69 etc., we can provide logging approach to select the favorable shale in?tervals for fracturing.
Shale brittleness is one of the most important evaluation factors in shale oil and gas exploration and development. For shale brittleness, the rock mechanics experiment is the main way at present，however, in this paper, we developed a new method of X-ray element logging technique to evaluate in element level. Based on the element composition and correlation between element and mineral, it is revealed that the Si, Ca, Mg element can reflect the content of quartz, calcite and dolomite respectively, which establishes the theory of evaluating shale brittleness by means of X-ray element logging. By means of appropriate method to calculate the silica index, carbonate index and brittleness index to reflect the content of rigidity mineral, we can realize the shale brittleness evaluation while drilling. In accordance with the shale petrology of Shengli oilfield and shale brittleness evaluation standards, the carbonate index is selected to evaluate the shale brittleness so as to establish the four class criterion(CI ≥0.6，high；0.4≤CI＜0.6，medium；0.2≤CI＜0.4，lower；CI＜0.2，low）. After application of this technique in well NY1 and L69 etc., we can provide logging approach to select the favorable shale in?tervals for fracturing.
2014, 21(1):28-32.
Abstract:
In order to further discuss the relationship between overpressure system in continental rifted basins and hydrocarbon accumulation, we take the Chexi area of Chezhen depression as an example. Based on definition of the distribution characteristic of overpressure system, we analyzed the overpressure system which has made an important contribution to hydrocarbon accumulation, such as influence on hydrocarbon expulsion, force of hydrocarbon migration and location of hydrocarbon accumulation. The result showed that,the overpressure system in Chexi area has three architectures, peripherally distributed and centering the generation center. The research of relationship between overpressure system and hydrocarbon accumulation showed that the overpressure system occurs as two hydrocarbon expulsion models, including internal overpressure stable hydrocarbon expulsion and convex overpressure episodic hydrocarbon expulsion. Overpressure is the main migration force for primary hydrocarbon migration and downward migration. In overpressure basins, the plane distribution and vertical collocation of overpressure control the dominant migratory direction and accumulation scale.Finally, the hydrocarbon accumulation model of overpressure source and centrifugal pump is established, and it is viewed that the favorable pressure collocation internal overpressure and the reasonable collocation between pressure-released region and available reservoir under overpressure are the potential areas for hydrocarbon accumulation. The research has not only deeply recognized the law of hydrocarbon accumulation in overpressure system in Chexi area of Chezhen depression, but also offered significance for petroleum exploration in other continental rifted basins.
In order to further discuss the relationship between overpressure system in continental rifted basins and hydrocarbon accumulation, we take the Chexi area of Chezhen depression as an example. Based on definition of the distribution characteristic of overpressure system, we analyzed the overpressure system which has made an important contribution to hydrocarbon accumulation, such as influence on hydrocarbon expulsion, force of hydrocarbon migration and location of hydrocarbon accumulation. The result showed that,the overpressure system in Chexi area has three architectures, peripherally distributed and centering the generation center. The research of relationship between overpressure system and hydrocarbon accumulation showed that the overpressure system occurs as two hydrocarbon expulsion models, including internal overpressure stable hydrocarbon expulsion and convex overpressure episodic hydrocarbon expulsion. Overpressure is the main migration force for primary hydrocarbon migration and downward migration. In overpressure basins, the plane distribution and vertical collocation of overpressure control the dominant migratory direction and accumulation scale.Finally, the hydrocarbon accumulation model of overpressure source and centrifugal pump is established, and it is viewed that the favorable pressure collocation internal overpressure and the reasonable collocation between pressure-released region and available reservoir under overpressure are the potential areas for hydrocarbon accumulation. The research has not only deeply recognized the law of hydrocarbon accumulation in overpressure system in Chexi area of Chezhen depression, but also offered significance for petroleum exploration in other continental rifted basins.
2014, 21(1):33-35.
Abstract:
Weibull model is an important forecasting model, and it can forecast production and recoverable reserves. The model has three undetermined constants, which belong to the nonlinear model. In the past, the linear iterative or nonlinear iterative method is needed to solve it, however, the two methods above are complex and have some uncertainties. Based on the basic equations of Weibull model, the dimensionless formula is established by theoretical derivation, type curves for manual or automatic matching by computer are set up, which have only one undetermined constant. According to the matched model constant, the production, cumulative production and recoverable reserves of oil and gas fields can be forecasted. The application of field example indicated that, the content and methods in the paper are correct and effective.
Weibull model is an important forecasting model, and it can forecast production and recoverable reserves. The model has three undetermined constants, which belong to the nonlinear model. In the past, the linear iterative or nonlinear iterative method is needed to solve it, however, the two methods above are complex and have some uncertainties. Based on the basic equations of Weibull model, the dimensionless formula is established by theoretical derivation, type curves for manual or automatic matching by computer are set up, which have only one undetermined constant. According to the matched model constant, the production, cumulative production and recoverable reserves of oil and gas fields can be forecasted. The application of field example indicated that, the content and methods in the paper are correct and effective.
2014, 21(1):36-39.
Abstract:
Considering the actual conditions of irregular well pattern and heterogeneity in reservoir, and based on the reservoir engineering theory, a method to predict the residual oil distribution and dynamic development indexes has been proposed herein. The method first splits the oil field into multiple units dynamically and the units can be equivalent to homogeneous one, so that, we can use the Buckley-Leverett waterflooding theory to predict the dynamic development indexes of every unit and then calculate the entire reservoir development indexes. Compared with the numerical simulation method, the new procedure runs more quickly and requires less computer memory. The analysis on the application of theory above in an oil reservoir with 16 wells shows that the results of the method are basi?cally consistent with the numerical simulation method, which is of significant value for field application.
Considering the actual conditions of irregular well pattern and heterogeneity in reservoir, and based on the reservoir engineering theory, a method to predict the residual oil distribution and dynamic development indexes has been proposed herein. The method first splits the oil field into multiple units dynamically and the units can be equivalent to homogeneous one, so that, we can use the Buckley-Leverett waterflooding theory to predict the dynamic development indexes of every unit and then calculate the entire reservoir development indexes. Compared with the numerical simulation method, the new procedure runs more quickly and requires less computer memory. The analysis on the application of theory above in an oil reservoir with 16 wells shows that the results of the method are basi?cally consistent with the numerical simulation method, which is of significant value for field application.
2014, 21(1):40-44.
Abstract:
In response to the energy and economy requirement of China, the high and stable production of Tarim oilfield is directly connected to the oil supply and economic growth. So far, some blocks have entered a new development stage with high water cut and high oil recovery. Finding suitable substitute technique is of important significance for slowing down the production rate decline, and maintaining the stable production of crude oil, and reducing our dependence on imported oil. The Tarim oilfield is rich in natural gas, however, it has disadvantages, such as high pressure high temperature, high salinity and high content of calcium and magnesium. Consequently, based on the geological features of reservoirs and development status, the development situation of Tarim oilfield now facing is analyzed, and technical ideas of gas injection to enhance oil recovery are proposed. In view of the existing problems encountered in the study and applications of gas injection, and for the improvement of crude oil displacement performance, six suggestions, such as optimization of gas source and target block, preparation of gas injection, selection of injection types and methods, physical and numerical sim? ulation and gas injection formulating, field test and matching techniques, and gas storage theory are introduced to develop oil reservoirs.
In response to the energy and economy requirement of China, the high and stable production of Tarim oilfield is directly connected to the oil supply and economic growth. So far, some blocks have entered a new development stage with high water cut and high oil recovery. Finding suitable substitute technique is of important significance for slowing down the production rate decline, and maintaining the stable production of crude oil, and reducing our dependence on imported oil. The Tarim oilfield is rich in natural gas, however, it has disadvantages, such as high pressure high temperature, high salinity and high content of calcium and magnesium. Consequently, based on the geological features of reservoirs and development status, the development situation of Tarim oilfield now facing is analyzed, and technical ideas of gas injection to enhance oil recovery are proposed. In view of the existing problems encountered in the study and applications of gas injection, and for the improvement of crude oil displacement performance, six suggestions, such as optimization of gas source and target block, preparation of gas injection, selection of injection types and methods, physical and numerical sim? ulation and gas injection formulating, field test and matching techniques, and gas storage theory are introduced to develop oil reservoirs.
11 Proration optimization of production and injection rate based on sequential quadratic programming
2014, 21(1):45-50.
Abstract:
Optimizing the oilfield working system has become one of the most effective ways to maximize the oilfield profits. In order to improve the efficiency of the production optimization and handle the nonlinear inequality constraints, this paper applied sequential quadratic programming algorithm to this study area. The sequential quadratic programming algorithm will transform the nonlinear optimization problem that seeks the optimal value of the variable into a series of quadratic programming sub-problems that locates the searching directions of the variables. The gradients of the augmented Lagrange function, used in the construction of the QP sub-problems with respect to the variables, are calculated by the adjoint method while the Hessen matrix is updated using BFGS method. By solving the QP sub-problems, the searching directions of the control variables are then obtained which can be used to adjust the initial vari?ables and finally to locate the optimal values of control variables. The new method has not only super linear convergence speed, but also combines the advantages of adjoint method which can efficiently calculate the gradients even in the case of a large number of parameters. In this paper, a two-dimensional three-phase reservoir model is tested to verify the validity of the method. The displacement results of optimized development plans under total injection and production rate equality constraints and inequality constraints show that,the field cumulative water injection amount of the former is less than that of the latter by 18 percent, and the field cumulative oil production amount of the former is higher than the latter by 14%. However, the pressure in the former has fallen dramatically which would easily lead to energy shortage in the late development stage. In order to get reasonable development performance, we should do production optimization under total injection and production equality constraints or add lower limit constraints to the inequality constraints.The theory is also applied to a real oil field and the total injection rate is set with equality constraints. The recovery has increased by 0.92% and the NPV has increased by 35% after the optimization.
Optimizing the oilfield working system has become one of the most effective ways to maximize the oilfield profits. In order to improve the efficiency of the production optimization and handle the nonlinear inequality constraints, this paper applied sequential quadratic programming algorithm to this study area. The sequential quadratic programming algorithm will transform the nonlinear optimization problem that seeks the optimal value of the variable into a series of quadratic programming sub-problems that locates the searching directions of the variables. The gradients of the augmented Lagrange function, used in the construction of the QP sub-problems with respect to the variables, are calculated by the adjoint method while the Hessen matrix is updated using BFGS method. By solving the QP sub-problems, the searching directions of the control variables are then obtained which can be used to adjust the initial vari?ables and finally to locate the optimal values of control variables. The new method has not only super linear convergence speed, but also combines the advantages of adjoint method which can efficiently calculate the gradients even in the case of a large number of parameters. In this paper, a two-dimensional three-phase reservoir model is tested to verify the validity of the method. The displacement results of optimized development plans under total injection and production rate equality constraints and inequality constraints show that,the field cumulative water injection amount of the former is less than that of the latter by 18 percent, and the field cumulative oil production amount of the former is higher than the latter by 14%. However, the pressure in the former has fallen dramatically which would easily lead to energy shortage in the late development stage. In order to get reasonable development performance, we should do production optimization under total injection and production equality constraints or add lower limit constraints to the inequality constraints.The theory is also applied to a real oil field and the total injection rate is set with equality constraints. The recovery has increased by 0.92% and the NPV has increased by 35% after the optimization.
2014, 21(1):51-54.
Abstract:
Miscible and/or near miscible gas injection processes are those among the most widely used enhanced oil recovery techniques. And, a CO2-oil miscible flooding is more effective to enhance the local displacement efficiency. The successful design and implementation of a miscible CO2 injection project is dependent upon the accurate determination of MMP（minimum miscibility pressure）, the pressure above which the displacement process becomes multicontact miscible. This paper considers the multicontact process during the miscible flooding, and presents a method to get the characteristics curve of multicontact, and analyzes the character of characteristics curve for CO2 flooding, and combines some main factor (reservoir temperature, oil composition) that may infect MMP,then, we suggest a correlation to make a prediction for the minimum value of characteristics curve of multicontact. Based on the work above, we suggest a new method to predict MMP for CO2 flooding. Our method needn’t locate the key tie lines, and avoid the unfavorable factors existing in the MOC and the mixing-cell method which leads to the failure of MMP prediction, so as to overcome the shortcoming of traditional correlation which didn’t consider the process of multicontact. For all of these reasons, our method becomes more practical and more accurate. The prediction error for our method is within 8%.
Miscible and/or near miscible gas injection processes are those among the most widely used enhanced oil recovery techniques. And, a CO2-oil miscible flooding is more effective to enhance the local displacement efficiency. The successful design and implementation of a miscible CO2 injection project is dependent upon the accurate determination of MMP（minimum miscibility pressure）, the pressure above which the displacement process becomes multicontact miscible. This paper considers the multicontact process during the miscible flooding, and presents a method to get the characteristics curve of multicontact, and analyzes the character of characteristics curve for CO2 flooding, and combines some main factor (reservoir temperature, oil composition) that may infect MMP,then, we suggest a correlation to make a prediction for the minimum value of characteristics curve of multicontact. Based on the work above, we suggest a new method to predict MMP for CO2 flooding. Our method needn’t locate the key tie lines, and avoid the unfavorable factors existing in the MOC and the mixing-cell method which leads to the failure of MMP prediction, so as to overcome the shortcoming of traditional correlation which didn’t consider the process of multicontact. For all of these reasons, our method becomes more practical and more accurate. The prediction error for our method is within 8%.
2014, 21(1):55-58.
Abstract:
The particle size and size distribution of pore-scale elastic microspheres are studied through laser particle size analyzer; using RheoStress600 rotary rheometer and M5600 rheometer, the creep-recovery property of elastic microspheres and their viscous modulus and elastic modulus variation at different frequency and temperature are tested respectively; through the LVDV-II+Pro rotating viscometer, the effect of concentration, temperature, shear rate, salinity on viscosity of elastic microspheres solution are studied. The results show that the elastic microspheres synthesized in laboratory are micron pore-scale feature which matche with the reservoir rock and obey the Weibull distribution. They have better creep-recovery property and viscoelasticity; and the elastic microspheres solution behaves as a pseudoplastic liquid at low temperature and low shear rate condition, moreover, it behaves as an expansibility liquid at middle shear rate condition or high temperature and low shear rate condition, and shows similar Newtonian fluid feature at high shear rate condition; the viscosity of elastic microspheres solution is lower with good mobility and can be injected easily in the process of profile control and flooding; the elastic microspheres solution has better stability and can be used for high temperature and high salinity reservoirs to enhance oil recovery with good reservoir adaptability.
The particle size and size distribution of pore-scale elastic microspheres are studied through laser particle size analyzer; using RheoStress600 rotary rheometer and M5600 rheometer, the creep-recovery property of elastic microspheres and their viscous modulus and elastic modulus variation at different frequency and temperature are tested respectively; through the LVDV-II+Pro rotating viscometer, the effect of concentration, temperature, shear rate, salinity on viscosity of elastic microspheres solution are studied. The results show that the elastic microspheres synthesized in laboratory are micron pore-scale feature which matche with the reservoir rock and obey the Weibull distribution. They have better creep-recovery property and viscoelasticity; and the elastic microspheres solution behaves as a pseudoplastic liquid at low temperature and low shear rate condition, moreover, it behaves as an expansibility liquid at middle shear rate condition or high temperature and low shear rate condition, and shows similar Newtonian fluid feature at high shear rate condition; the viscosity of elastic microspheres solution is lower with good mobility and can be injected easily in the process of profile control and flooding; the elastic microspheres solution has better stability and can be used for high temperature and high salinity reservoirs to enhance oil recovery with good reservoir adaptability.
2014, 21(1):59-62.
Abstract:
The waterflooding and replacing oil is currently the chief method of enhancing oil recovery in the single well fracture-vuggy units in Tahe oilfield. But, the proportion of failure wells increases gradually, and then it influences greatly the effect of waterflooding performance. Through analyzing the mechanism of water injection for oil to improve the development effect and combined with the production characteristics, the main failures can be summarized. The main characteristics that may cause the wells ineffective are, the watercut rising quickly, the upturned of cyclic water injection instruction curve, the gradually decrease of the cyclic water storage rate, the dramatically increase of the cyclic water replacing for a ton of oil. For the water injection wells, the main objective causes accounting for the failure are: reservoir type of individual well and bottom water intrusion in late stage of water injection to replace oil; and too much injection of cyclic water injection in wells, and inappropriate cyclic injection production parameters caused by insufficient soaking subjectively.
The waterflooding and replacing oil is currently the chief method of enhancing oil recovery in the single well fracture-vuggy units in Tahe oilfield. But, the proportion of failure wells increases gradually, and then it influences greatly the effect of waterflooding performance. Through analyzing the mechanism of water injection for oil to improve the development effect and combined with the production characteristics, the main failures can be summarized. The main characteristics that may cause the wells ineffective are, the watercut rising quickly, the upturned of cyclic water injection instruction curve, the gradually decrease of the cyclic water storage rate, the dramatically increase of the cyclic water replacing for a ton of oil. For the water injection wells, the main objective causes accounting for the failure are: reservoir type of individual well and bottom water intrusion in late stage of water injection to replace oil; and too much injection of cyclic water injection in wells, and inappropriate cyclic injection production parameters caused by insufficient soaking subjectively.
2014, 21(1):63-65.
Abstract:
The polymer microgels are a kind of agents, which has a role of improving reservoir heterogeneity and enhancing oil recovery. This new laboratory studies reported in this paper aimed at knowing how the polymer microgels propagate in porous media by artificial conglomerate cores experiments with multiple pressure measurement and the size distribution of microgels in yielding fluid. The results show that the maximum resistance factors are 5.3 and 8.5 respectively, while the polymer microgels propagate within the artificial conglomerate cores. There is only single peak, in which the highest peak is 5 μm in the yielding fluid of the core with permeability of 0.295 7 μm2. Furthermore, the double peaks appeared, in which the highest peaks are 7 and 150 μm respectively in the yielding fluid from the core with permeability of 0. 634 5 μm2. It is a good way on how to choose the size of polymer microgels in the field application of polymer microgels flooding.
The polymer microgels are a kind of agents, which has a role of improving reservoir heterogeneity and enhancing oil recovery. This new laboratory studies reported in this paper aimed at knowing how the polymer microgels propagate in porous media by artificial conglomerate cores experiments with multiple pressure measurement and the size distribution of microgels in yielding fluid. The results show that the maximum resistance factors are 5.3 and 8.5 respectively, while the polymer microgels propagate within the artificial conglomerate cores. There is only single peak, in which the highest peak is 5 μm in the yielding fluid of the core with permeability of 0.295 7 μm2. Furthermore, the double peaks appeared, in which the highest peaks are 7 and 150 μm respectively in the yielding fluid from the core with permeability of 0. 634 5 μm2. It is a good way on how to choose the size of polymer microgels in the field application of polymer microgels flooding.
2014, 21(1):66-69.
Abstract:
There is plenty of low resistivity reservoir in the western south China sea, it is difficult to identify and evaluate the low resistivity reservoir effectively using the conventional logging data, according to the logging response characteristics of low resistivity reservoir. This paper analyzed the macro feature and microscopic pore structure of formation combined with the core data, and pointed out that the main geologic origin for the property of low resistivity is the high content of clay and bound water. In response to the identification and evaluation of low resistivity reservoir, firstly, we applied the ΔlgR technology which is usually used in logging evaluation of source rock, the second is multiple mineral analysis to construct the multiple mineral model by choosing the appropriate component of formation mineral and fluid, so as to solve the equations based on the principle of least square and optimization technique, so, we can get multiple mineral section and reservoir parameter, combining with the characteristic of NMR T2 spectra, the distribution of pore size,clay water and bound water and others NMR logging results, finally, we make comprehensive estimation for low resistivity reservoir based on the qualitative identification and tested by production. We calculate the reservoir parameters including the shale content, porosity, total saturation, mobile fluid saturation, clay water saturation and the volume content of all kinds of rock mineralogical composition in the formation, then, using the sealed coring data to calibrate the final interpretation, and ascertaining that there is a good consistency between them. The result indicates that the methods we used in the paper can offer an effective identification and quantitative evaluation for the low resistivity reservoir.
There is plenty of low resistivity reservoir in the western south China sea, it is difficult to identify and evaluate the low resistivity reservoir effectively using the conventional logging data, according to the logging response characteristics of low resistivity reservoir. This paper analyzed the macro feature and microscopic pore structure of formation combined with the core data, and pointed out that the main geologic origin for the property of low resistivity is the high content of clay and bound water. In response to the identification and evaluation of low resistivity reservoir, firstly, we applied the ΔlgR technology which is usually used in logging evaluation of source rock, the second is multiple mineral analysis to construct the multiple mineral model by choosing the appropriate component of formation mineral and fluid, so as to solve the equations based on the principle of least square and optimization technique, so, we can get multiple mineral section and reservoir parameter, combining with the characteristic of NMR T2 spectra, the distribution of pore size,clay water and bound water and others NMR logging results, finally, we make comprehensive estimation for low resistivity reservoir based on the qualitative identification and tested by production. We calculate the reservoir parameters including the shale content, porosity, total saturation, mobile fluid saturation, clay water saturation and the volume content of all kinds of rock mineralogical composition in the formation, then, using the sealed coring data to calibrate the final interpretation, and ascertaining that there is a good consistency between them. The result indicates that the methods we used in the paper can offer an effective identification and quantitative evaluation for the low resistivity reservoir.
2014, 21(1):70-73.
Abstract:
A new low-tension foam flooding system is developed for high-temperature and high-salinity reservoir using molecular simulation and in-home experiments. Under the conditions of 80 °C, the foam volume maintained at 200 mL and half-life >5 000 s, implying that the foam system has great foaming capability and foam stability. A one-month single-well test with low-tension nitrogen foam flooding is carried out at Shengtuo field on August 30, 2011. The foaming capability and foam stability of foam system under different conditions are investigated. The plugging ability for high-permeability streaks is examined as well. The injection mode and gas/liquid ratio are optimized. The cumulative injection of foaming agent is 2 087 m3. The average water cut of 3 influential producers decreased from 98.5% to 97.8%. The average fluid production is stable and oil production increases from 6.3 to 9.2 t/d. According to the perfor?mance of injectors and producers and the variation of injection profile, the low-tension foam system can form stable foam and exhibit good blocking efficiency for high-permeability streaks. The gas-liquid mixed injection can improve percolating resistance and plugging ability. The optimal gas/liquid ratio under test condition is 1∶1.
A new low-tension foam flooding system is developed for high-temperature and high-salinity reservoir using molecular simulation and in-home experiments. Under the conditions of 80 °C, the foam volume maintained at 200 mL and half-life >5 000 s, implying that the foam system has great foaming capability and foam stability. A one-month single-well test with low-tension nitrogen foam flooding is carried out at Shengtuo field on August 30, 2011. The foaming capability and foam stability of foam system under different conditions are investigated. The plugging ability for high-permeability streaks is examined as well. The injection mode and gas/liquid ratio are optimized. The cumulative injection of foaming agent is 2 087 m3. The average water cut of 3 influential producers decreased from 98.5% to 97.8%. The average fluid production is stable and oil production increases from 6.3 to 9.2 t/d. According to the perfor?mance of injectors and producers and the variation of injection profile, the low-tension foam system can form stable foam and exhibit good blocking efficiency for high-permeability streaks. The gas-liquid mixed injection can improve percolating resistance and plugging ability. The optimal gas/liquid ratio under test condition is 1∶1.
2014, 21(1):74-77.
Abstract:
Surfactant with higher mass concentration from 1 000 mg/L to 3 000 mg/L is always used in ASP or SP flooding for getting ultra-low interfacial tension. Using surfactant with higher concentration does not always enhance the oil recovery, although it increases the cost of production. Through six displacement experiments, the most appropriate systems for Nanyang oilfield are selected. Using low concentration surfactant can improve the recovery efficiency significantly .The alkali/surfactant/polymer system can improve oil recovery by 22.3%, better than that of surfactant/polymer system, alkali/polymer system and polymer system. Before the displacement experiments, the oil-water interfacial tension, viscosity and viscoelasticity of flooding systems are tested. The conclusions are as follows: first,low-concentration surfactant can lower the interfacial tension to below 10-2 mN/m; second, the surfactant and the alkali used in this experiment can both influence the viscosity and viscoelasticity of the polymer.
Surfactant with higher mass concentration from 1 000 mg/L to 3 000 mg/L is always used in ASP or SP flooding for getting ultra-low interfacial tension. Using surfactant with higher concentration does not always enhance the oil recovery, although it increases the cost of production. Through six displacement experiments, the most appropriate systems for Nanyang oilfield are selected. Using low concentration surfactant can improve the recovery efficiency significantly .The alkali/surfactant/polymer system can improve oil recovery by 22.3%, better than that of surfactant/polymer system, alkali/polymer system and polymer system. Before the displacement experiments, the oil-water interfacial tension, viscosity and viscoelasticity of flooding systems are tested. The conclusions are as follows: first,low-concentration surfactant can lower the interfacial tension to below 10-2 mN/m; second, the surfactant and the alkali used in this experiment can both influence the viscosity and viscoelasticity of the polymer.
2014, 21(1):78-80.
Abstract:
Along with the development of oil and gas field, most blocks enter into the high water cut stage, and even very high water cut stage. Thin and low productive reservoirs are the potential reservoir by means of water flooding instead of the middle and high permeable reservoirs in low and medium water cut stage. With the imperfect injection-production relationship, low formation pressure, and low degree of producing reserves on thin and poor reservoirs. Taking the Xing6 east block of Daqing oilfield for example, the effective injection-production well spacing with different permeability is calculated by reservoir engineering methods, based on the flow tube model, the effective producing coefficient of different ratio of space between wells and rows for rhombus five-spot well pattern is solved. The results show that, the permeability of thin and poor reservoir is 12×10-3 μm2, and the corresponding effective injection-production well spacing is 180m, and the reasonable ratio of space between wells and rows is 1.8. The numerical models test and verify the results of theoretical methods, that is, the ratio is 1.8, the recovery factor is highest, the sweeping scope is large, and the water breakthrough time is earliest.
Along with the development of oil and gas field, most blocks enter into the high water cut stage, and even very high water cut stage. Thin and low productive reservoirs are the potential reservoir by means of water flooding instead of the middle and high permeable reservoirs in low and medium water cut stage. With the imperfect injection-production relationship, low formation pressure, and low degree of producing reserves on thin and poor reservoirs. Taking the Xing6 east block of Daqing oilfield for example, the effective injection-production well spacing with different permeability is calculated by reservoir engineering methods, based on the flow tube model, the effective producing coefficient of different ratio of space between wells and rows for rhombus five-spot well pattern is solved. The results show that, the permeability of thin and poor reservoir is 12×10-3 μm2, and the corresponding effective injection-production well spacing is 180m, and the reasonable ratio of space between wells and rows is 1.8. The numerical models test and verify the results of theoretical methods, that is, the ratio is 1.8, the recovery factor is highest, the sweeping scope is large, and the water breakthrough time is earliest.
2014, 21(1):81-83.
Abstract:
In the offshore Chengdao oilfield, the oil reservoir of Guantao member is consisted of high porosity and permeability sandstone. Due to the high speed oil development, the water cut increased quickly. In this paper, we used the elastic microspheres of seawater based to evaluate the matching relationship between the pore-scale and the feature of elastic-microspheres, the viscosity, and the double-tube driving test. The results suggested that the initial particle size of the elastic-microsphere is 1/3-1/7 times of the pore diameter, after 10-15 days, the microsphere particle size expands to 1.4-1.5 times of the pore diameter, which can plug the pore effectively.The initial viscosity of the microsphere solution is about 1 mPa ? s, that can come into the layer deeply. It is applied in CB25A test area with online mode for deep profile controlling technology. After 0.01 times pore volume flooding injection, the well’s water pressure increased by 1-2 MPa, and the full-deep improved by 0.22-0.57. In the corresponding 11 wells, 9 are enhanced by this technique, and the average water cut is reduced by 7.6%, moreover, the recovery performance is still enhanced even after 4 years of subsequent water flooding. The elastic-microspheres of deep flooding to the oil stabilization and water control of offshore oilfield are of durable performance.
In the offshore Chengdao oilfield, the oil reservoir of Guantao member is consisted of high porosity and permeability sandstone. Due to the high speed oil development, the water cut increased quickly. In this paper, we used the elastic microspheres of seawater based to evaluate the matching relationship between the pore-scale and the feature of elastic-microspheres, the viscosity, and the double-tube driving test. The results suggested that the initial particle size of the elastic-microsphere is 1/3-1/7 times of the pore diameter, after 10-15 days, the microsphere particle size expands to 1.4-1.5 times of the pore diameter, which can plug the pore effectively.The initial viscosity of the microsphere solution is about 1 mPa ? s, that can come into the layer deeply. It is applied in CB25A test area with online mode for deep profile controlling technology. After 0.01 times pore volume flooding injection, the well’s water pressure increased by 1-2 MPa, and the full-deep improved by 0.22-0.57. In the corresponding 11 wells, 9 are enhanced by this technique, and the average water cut is reduced by 7.6%, moreover, the recovery performance is still enhanced even after 4 years of subsequent water flooding. The elastic-microspheres of deep flooding to the oil stabilization and water control of offshore oilfield are of durable performance.
2014, 21(1):84-86.
Abstract:
Long-length fractured vertical well has been applied widely, but there is still not productivity prediction model for longlength fractured vertical well in the low permeability oil reservoirs. In view of the fluid flow mechanism around the vertically fractured well, the productivity prediction model of long-length fractured vertical well with infinite conductivity and finite conductivity is derived by using conformal transformation and bilinear flow theory in consideration of starting pressure gradient. The IPR curve is draw to analyze the influences of hydraulic fractured parameters on long-length fractured vertical well productivity. Combined with the actual example, the accuracy of this prediction model is verified. The well productivity is influenced by the fracture length more deeply than the fracture conductivity, and there is an optimal fracture conductivity for long-length fractured vertical well under certain fracture length.
Long-length fractured vertical well has been applied widely, but there is still not productivity prediction model for longlength fractured vertical well in the low permeability oil reservoirs. In view of the fluid flow mechanism around the vertically fractured well, the productivity prediction model of long-length fractured vertical well with infinite conductivity and finite conductivity is derived by using conformal transformation and bilinear flow theory in consideration of starting pressure gradient. The IPR curve is draw to analyze the influences of hydraulic fractured parameters on long-length fractured vertical well productivity. Combined with the actual example, the accuracy of this prediction model is verified. The well productivity is influenced by the fracture length more deeply than the fracture conductivity, and there is an optimal fracture conductivity for long-length fractured vertical well under certain fracture length.
22 Experiment on reasonable capillary number for binary compound flooding in heterogeneous reservoir
2014, 21(1):87-91.
Abstract:
In order to study the influence of capillary number on binary compound flooding system final oil recovery in the heterogeneous reservoir, the binary compound flooding experiments for different viscosities and interfacial tensions are carried out to evaluate the capacity so as to enhance the oil recovery in the heterogeneous reservoir with different capillary numbers(10-6-100)，and the differences of flooding process among different capillary number formulas are compared by microscopic visualization physical model. The flooding result shows that when the interfacial tensions are the same, the higher the viscosity, the higher oil recovery, but there exists a critical viscosity of binary compound flooding. The increment of oil recovery becomes stable when the critical viscosity is reached, and when the viscosity of binary compound system is smaller than critical viscosity, the lower the interfacial tension, the higher oil recovery increment; when the viscosity of binary compound system is higher than critical viscosity, there is a reasonable interfacial tension of binary compound system, and the oil recovery reaches maximum at the reasonable interfacial tension (1.865×10-2 mN/m). The oil recovery reaches the highest at critical viscosity and reasonable interfacial tension, and the reasonable capillary number is obtained. The microscopic visualization physical simulation experiment shows the reasonable capillary number formula. The formula with this capillary number has certain oil-washing ability，besides, the emulsion formed with this formula has profile control capacity on the target reser?voir.
In order to study the influence of capillary number on binary compound flooding system final oil recovery in the heterogeneous reservoir, the binary compound flooding experiments for different viscosities and interfacial tensions are carried out to evaluate the capacity so as to enhance the oil recovery in the heterogeneous reservoir with different capillary numbers(10-6-100)，and the differences of flooding process among different capillary number formulas are compared by microscopic visualization physical model. The flooding result shows that when the interfacial tensions are the same, the higher the viscosity, the higher oil recovery, but there exists a critical viscosity of binary compound flooding. The increment of oil recovery becomes stable when the critical viscosity is reached, and when the viscosity of binary compound system is smaller than critical viscosity, the lower the interfacial tension, the higher oil recovery increment; when the viscosity of binary compound system is higher than critical viscosity, there is a reasonable interfacial tension of binary compound system, and the oil recovery reaches maximum at the reasonable interfacial tension (1.865×10-2 mN/m). The oil recovery reaches the highest at critical viscosity and reasonable interfacial tension, and the reasonable capillary number is obtained. The microscopic visualization physical simulation experiment shows the reasonable capillary number formula. The formula with this capillary number has certain oil-washing ability，besides, the emulsion formed with this formula has profile control capacity on the target reser?voir.
2014, 21(1):92-94.
Abstract:
In view of upper Guantao sandbody in west block7 of Gudong oilfield, hierarchical interfaces of the sandbodies in the studied area are classified and recognized on the basis of core observation and dynamic analysis，and the study indicates that the effective permeability of long axis positive side and center of mid-channel bar are more favorable, and the effective permeability of sideband of mid-channel bar is lower, so sideband of mid-channel bar may concentrate the remaining oil. The experimental data is used to characterize how the log response is affected by polymer, and the study also indicates that the log response is not effected by the polymer, but it is affected by the polymer small clumps which are accumulated by polymer containing clean water due to uneven driving, and the polymer small clumps mainly appear at sideband of reservoir architecture, and the log response of polymer small clumps is high in resistance. So, the reservoir architecture and the well logging analysis techniques are used to identify the remaining oil. The research report indicates that the sideband of reservoir architecture cell can concentrate remaining oil or polymer, C/O well logging or other methods that can identify oil and polymer are suggested to be used.
In view of upper Guantao sandbody in west block7 of Gudong oilfield, hierarchical interfaces of the sandbodies in the studied area are classified and recognized on the basis of core observation and dynamic analysis，and the study indicates that the effective permeability of long axis positive side and center of mid-channel bar are more favorable, and the effective permeability of sideband of mid-channel bar is lower, so sideband of mid-channel bar may concentrate the remaining oil. The experimental data is used to characterize how the log response is affected by polymer, and the study also indicates that the log response is not effected by the polymer, but it is affected by the polymer small clumps which are accumulated by polymer containing clean water due to uneven driving, and the polymer small clumps mainly appear at sideband of reservoir architecture, and the log response of polymer small clumps is high in resistance. So, the reservoir architecture and the well logging analysis techniques are used to identify the remaining oil. The research report indicates that the sideband of reservoir architecture cell can concentrate remaining oil or polymer, C/O well logging or other methods that can identify oil and polymer are suggested to be used.
2014, 21(1):95-98.
Abstract:
In this paper, it investigates the effect of complexing agent on the viscosity and oil-water interfacial tension of partially hydrolyzed polyacrylamide HPAM and linear alkyl betaine BH systems, and discusses the method of utilizing complexing agent as additive to improve the increasing viscosity ability and interfacial property of polymer and surfactant flooding system in high salinity reservoir. It has been found that the viscosity of 1 800 mg/L HPAM may be increased by more than 80%, and the minimum of dynamic interfacial tension between BH surfactant solution and crude oil may be reduced from 10-2 mN/m magnitude to ultralow level by addition of only 50 mg/L complexing agent in salt water containing NaCl 6 500 mg/L, CaCl2 890 mg/L and MgCl2 520 mg/L respectively, which is also suitable for HPAM and BH mixed system. By studying the variation of aging viscosity and dynamic interfacial tension, the action mechanism of complexing agent is further analyzed.
In this paper, it investigates the effect of complexing agent on the viscosity and oil-water interfacial tension of partially hydrolyzed polyacrylamide HPAM and linear alkyl betaine BH systems, and discusses the method of utilizing complexing agent as additive to improve the increasing viscosity ability and interfacial property of polymer and surfactant flooding system in high salinity reservoir. It has been found that the viscosity of 1 800 mg/L HPAM may be increased by more than 80%, and the minimum of dynamic interfacial tension between BH surfactant solution and crude oil may be reduced from 10-2 mN/m magnitude to ultralow level by addition of only 50 mg/L complexing agent in salt water containing NaCl 6 500 mg/L, CaCl2 890 mg/L and MgCl2 520 mg/L respectively, which is also suitable for HPAM and BH mixed system. By studying the variation of aging viscosity and dynamic interfacial tension, the action mechanism of complexing agent is further analyzed.
2014, 21(1):99-102.
Abstract:
For high-temperature and high-salinity reservoirs, the surfactant flooding is an important technical measure for enhancing oil recovery. But the study of emulsification effect on enhancing oil recovery was not given sufficient attention. To evaluate emulsification effect on oil recovery in Pucheng oilfield, two surfactants YD-G1 and SHY-1 are selected through the experiment of decreasing interfacial tension. The interfacial tensions between the two surfactants solution and Pucheng dehydrated and degassed crude oil can reach the ultra-low level of 10-3 mN/m before and after two surfactants solution putting into constant temperature oven of 120 ℃ in 30 days, which shows two surfactants have good thermal and salinity tolerance capability. Compared with the SHY-1 emulsion, the YDG1 emulsion of same mass fraction has lower water separating proportion, smaller average diameter, which shows YD-G1 solution stronger emulsification capability. The two kinds of emulsion are prepared by using dehydrated and degassed crude oil from Pucheng oilfield and the two surfactants. The YD-G1 solution which has stronger emulsifying ability has a better oil displacement effect than SHY-1,which illustrates that the emulsion is one of the key factors to enhance the recovery efficiency. The optimum injection concentration and volume are 0.3wt% and 0.5 PV by optimization of laboratory experiments. In the preferred injection mode, the surfactant flooding can improve the recovery factor of 13.5%.
For high-temperature and high-salinity reservoirs, the surfactant flooding is an important technical measure for enhancing oil recovery. But the study of emulsification effect on enhancing oil recovery was not given sufficient attention. To evaluate emulsification effect on oil recovery in Pucheng oilfield, two surfactants YD-G1 and SHY-1 are selected through the experiment of decreasing interfacial tension. The interfacial tensions between the two surfactants solution and Pucheng dehydrated and degassed crude oil can reach the ultra-low level of 10-3 mN/m before and after two surfactants solution putting into constant temperature oven of 120 ℃ in 30 days, which shows two surfactants have good thermal and salinity tolerance capability. Compared with the SHY-1 emulsion, the YDG1 emulsion of same mass fraction has lower water separating proportion, smaller average diameter, which shows YD-G1 solution stronger emulsification capability. The two kinds of emulsion are prepared by using dehydrated and degassed crude oil from Pucheng oilfield and the two surfactants. The YD-G1 solution which has stronger emulsifying ability has a better oil displacement effect than SHY-1,which illustrates that the emulsion is one of the key factors to enhance the recovery efficiency. The optimum injection concentration and volume are 0.3wt% and 0.5 PV by optimization of laboratory experiments. In the preferred injection mode, the surfactant flooding can improve the recovery factor of 13.5%.
2014, 21(1):103-106.
Abstract:
The“well factory”is becoming more and more concerned in the development of oil and gas field with its obvious advantages such as intensive well layout, small area cover, resources sharing, assembly line production, large-scale mass production, high runtime rate, instant gratification, obvious benefits. The tight conglomerate reservoir in Dongxin Yan227 has adopted the conventional methods at the early stage. Hydraulic fracturing is used to stimulate the vertical wells and deviated wells. Single well’s daily liquid yielding is 3 m3 /d, daily oil production is 1.2 t/d. The oil well productivity and the block’s oil production rate are low, and the economic performance is poor, as well as the poor development effect. Based on the problems above, the unconventional development method named “well factory”is intensively constructed in recent years. The centralized drilling, fracturing and producing mode is used. Through strengthening technology research and integrated application, focusing on the geological characteristics and the reservoir properties, the matching methods such as the well pattern optimization technology, the long well section of horizontal well technology, the optimized drilling technology and the multistage fracturing technology with pumping segment bridge plug and other unconventional techniques are carried on. The block reserve producing rate and single well productivity are greatly increased. This technology improves the development level of the low permeability conglomerate reservoir significantly, and provides the beneficial reference for the efficient development to similar reservoirs.
The“well factory”is becoming more and more concerned in the development of oil and gas field with its obvious advantages such as intensive well layout, small area cover, resources sharing, assembly line production, large-scale mass production, high runtime rate, instant gratification, obvious benefits. The tight conglomerate reservoir in Dongxin Yan227 has adopted the conventional methods at the early stage. Hydraulic fracturing is used to stimulate the vertical wells and deviated wells. Single well’s daily liquid yielding is 3 m3 /d, daily oil production is 1.2 t/d. The oil well productivity and the block’s oil production rate are low, and the economic performance is poor, as well as the poor development effect. Based on the problems above, the unconventional development method named “well factory”is intensively constructed in recent years. The centralized drilling, fracturing and producing mode is used. Through strengthening technology research and integrated application, focusing on the geological characteristics and the reservoir properties, the matching methods such as the well pattern optimization technology, the long well section of horizontal well technology, the optimized drilling technology and the multistage fracturing technology with pumping segment bridge plug and other unconventional techniques are carried on. The block reserve producing rate and single well productivity are greatly increased. This technology improves the development level of the low permeability conglomerate reservoir significantly, and provides the beneficial reference for the efficient development to similar reservoirs.
2014, 21(1):107-110.
Abstract:
Aiming at the challenges of poor capping rock, and in view of the development of lower aqueous layer and natural fractures of Fan134-1 well, the research and application of secondary sand fracturing technology are conducted to the well. According to reservoir geological features and well conditions, and based on the technical difficulties of fracturing operation on Fan134-1, the research is conducted with respect to proppant quantity, optimization of proppant ratio to the second operation, pump-stopped time, selection and evaluation of fracturing fluids and proppant, and supporting technical measures. The secondary sand fracturing operation is thereafter carried out on November 26, 2012. The operation lasted 189 minutes with accumulatively loading of 468 m3 fracturing fluids and 46 m3 proppant. The pump stopping time was 115 minutes. Three days after operation, the average fluid flowing production is achieved at 27.1 t/d, and average daily oil production at 13.2 t, the stimulation effect and the economic benefit are remarkable.
Aiming at the challenges of poor capping rock, and in view of the development of lower aqueous layer and natural fractures of Fan134-1 well, the research and application of secondary sand fracturing technology are conducted to the well. According to reservoir geological features and well conditions, and based on the technical difficulties of fracturing operation on Fan134-1, the research is conducted with respect to proppant quantity, optimization of proppant ratio to the second operation, pump-stopped time, selection and evaluation of fracturing fluids and proppant, and supporting technical measures. The secondary sand fracturing operation is thereafter carried out on November 26, 2012. The operation lasted 189 minutes with accumulatively loading of 468 m3 fracturing fluids and 46 m3 proppant. The pump stopping time was 115 minutes. Three days after operation, the average fluid flowing production is achieved at 27.1 t/d, and average daily oil production at 13.2 t, the stimulation effect and the economic benefit are remarkable.
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