Volume 24,Issue 2,2017 Table of Contents
2017, 24(2):1-7.
DOI: 10.13673/j.cnki.cn37-1359/te.2017.02.001
Abstract:
Ben1 oil reservoir and AG1 oil reservoir of Jake South Oilfield in Fula sag of Muglad Basin are typical complex fault-block oil reservoirs，which are anticline oil reservoir and layered oil reservoir developed in the complex fault block re?spectively. A number of low resistivity pays were ound in Ben1 oil reservoir and AG1 oil reservoir，which added to the difficulty of net pay identification. So the data，such as core data，test data and logging data，were comprehensively used to study the genesis and control factors of low resistivity pays. First，the reservoirs in Ben1 oil reservoir and AG1 oil reservoir were categorized according to their grain size，petrophysical properties，pore type and tightness，and low resistivity pays were defined in each type of reservoir. Then cores，thin sections，petrophysical data，SEM and X-ray diffraction data were comprehensively used to study the genesis of the low resistivity pays. Finally，the relationship between the identified low resistivity pays and the reservoir characteristics was studied to seek the controlling factors of its distribution. The results show that the main genesis of the low resistivity pays were high bound water saturation，low oil saturation caused by insufficient hydrocarbon charging and existence of conductive minerals，while additional conductivity of clay minerals and other engineering causes have little effects. The genesis of low resistivity pays found in different reservoir types and in different complex fault block types were different. The distribution of low resistivity pays was controlled by sedimentary microfacies，reservoir types and low resistivity pay belts，generally by one or two factors. The next exploration and development of the low resistivity oil layer in the study area should be mainly aimed at the high-quality reservoir in Ben1 oil reservoir and AG1 oil reservoir.
Ben1 oil reservoir and AG1 oil reservoir of Jake South Oilfield in Fula sag of Muglad Basin are typical complex fault-block oil reservoirs，which are anticline oil reservoir and layered oil reservoir developed in the complex fault block re?spectively. A number of low resistivity pays were ound in Ben1 oil reservoir and AG1 oil reservoir，which added to the difficulty of net pay identification. So the data，such as core data，test data and logging data，were comprehensively used to study the genesis and control factors of low resistivity pays. First，the reservoirs in Ben1 oil reservoir and AG1 oil reservoir were categorized according to their grain size，petrophysical properties，pore type and tightness，and low resistivity pays were defined in each type of reservoir. Then cores，thin sections，petrophysical data，SEM and X-ray diffraction data were comprehensively used to study the genesis of the low resistivity pays. Finally，the relationship between the identified low resistivity pays and the reservoir characteristics was studied to seek the controlling factors of its distribution. The results show that the main genesis of the low resistivity pays were high bound water saturation，low oil saturation caused by insufficient hydrocarbon charging and existence of conductive minerals，while additional conductivity of clay minerals and other engineering causes have little effects. The genesis of low resistivity pays found in different reservoir types and in different complex fault block types were different. The distribution of low resistivity pays was controlled by sedimentary microfacies，reservoir types and low resistivity pay belts，generally by one or two factors. The next exploration and development of the low resistivity oil layer in the study area should be mainly aimed at the high-quality reservoir in Ben1 oil reservoir and AG1 oil reservoir.
2017, 24(2):8-14.
DOI: 10.13673/j.cnki.cn37-1359/te.2017.02.002
Abstract:
Based on the comparison of outcrops and underground depositions of Fal structure in P Oilfield，South Sudan，outcrops of sandy braided-river reservoirs，found in Wuguantun，Datong City of Shanxi Province，were taken as a prototype model to be analyzed in detail through measuring and recording the actual geological profiles. The genetic types and distribution patterns of intercalations were recognized and summarized. On this basis，the impacts of restraining barrier and intercalation on the migration of edge and bottom water in the target area were discussed. The results show that there are five types of intercalations according to the genesis，including channel lag muddy gravel，fine-grained sediments of abandoned channel，fine-grained sediments of flood plain，fallen-silt overlaid mud and lateral accretion mud. Taking one single braided channel as the basic unit，the distribution patterns of intercalations were established，which are characterized as finegrained sediments of abandoned channel superimposed with braided sandbodies，fine-grained sediments of flood plain extending continuously to the outside of the river，fallen-silt overlaid-mud，lateral accretion mud and channel lag muddy gravels filling into the channel sandbodies due to their later erosion and modification. The distribution of fine-grained sediments of flood plain is the main factor preventing edge and bottom water breakthrough according to the distribution patterns of intercalations built for sandy braided-river reservoir in Fal structure，and the blocking effect on edge water becomes serious when intercalations occur with high frequency.
Based on the comparison of outcrops and underground depositions of Fal structure in P Oilfield，South Sudan，outcrops of sandy braided-river reservoirs，found in Wuguantun，Datong City of Shanxi Province，were taken as a prototype model to be analyzed in detail through measuring and recording the actual geological profiles. The genetic types and distribution patterns of intercalations were recognized and summarized. On this basis，the impacts of restraining barrier and intercalation on the migration of edge and bottom water in the target area were discussed. The results show that there are five types of intercalations according to the genesis，including channel lag muddy gravel，fine-grained sediments of abandoned channel，fine-grained sediments of flood plain，fallen-silt overlaid mud and lateral accretion mud. Taking one single braided channel as the basic unit，the distribution patterns of intercalations were established，which are characterized as finegrained sediments of abandoned channel superimposed with braided sandbodies，fine-grained sediments of flood plain extending continuously to the outside of the river，fallen-silt overlaid-mud，lateral accretion mud and channel lag muddy gravels filling into the channel sandbodies due to their later erosion and modification. The distribution of fine-grained sediments of flood plain is the main factor preventing edge and bottom water breakthrough according to the distribution patterns of intercalations built for sandy braided-river reservoir in Fal structure，and the blocking effect on edge water becomes serious when intercalations occur with high frequency.
2017, 24(2):15-21.
DOI: 10.13673/j.cnki.cn37-1359/te.2017.02.003
Abstract:
The geometrical deformation and tectonic evolution vary with different structural belts in the eastern segment of Kuqa depression. Based on the newest seismic data interpretation achievements，geometrical tectonic deformation characteristics of Tugerming and eastern Qiulitag tectonic zones located in the eastern segment of Kuqa depression were contrasted. On this basis，combined with the characteristics of growth strata and the transformation of regional dynamic environment，differential evolutional process and control factors of the two structural belts were investigated. The results show that the Tugerming tectonic belt is a faulted anticline developed above the hanging wall that is based on the Paleozoic uplift and basement-involved fault，which suffered tectonic reconstruction. There are few salt structures developed in Tugerming structural zone，and the whole deformations are relatively homogeneous. While the major tectonic deformation of eastern Qiulitage mainly occurred in the Neogene and salt structures are well developed，and hierarchical shrinked structural deformations are significant. The main factors leading to this difference are the size of tectonic stress，pre-existing structure and original thickness of salt rock.
The geometrical deformation and tectonic evolution vary with different structural belts in the eastern segment of Kuqa depression. Based on the newest seismic data interpretation achievements，geometrical tectonic deformation characteristics of Tugerming and eastern Qiulitag tectonic zones located in the eastern segment of Kuqa depression were contrasted. On this basis，combined with the characteristics of growth strata and the transformation of regional dynamic environment，differential evolutional process and control factors of the two structural belts were investigated. The results show that the Tugerming tectonic belt is a faulted anticline developed above the hanging wall that is based on the Paleozoic uplift and basement-involved fault，which suffered tectonic reconstruction. There are few salt structures developed in Tugerming structural zone，and the whole deformations are relatively homogeneous. While the major tectonic deformation of eastern Qiulitage mainly occurred in the Neogene and salt structures are well developed，and hierarchical shrinked structural deformations are significant. The main factors leading to this difference are the size of tectonic stress，pre-existing structure and original thickness of salt rock.
2017, 24(2):22-29.
DOI: 10.13673/j.cnki.cn37-1359/te.2017.02.004
Abstract:
Based on well logging，drilling，seismic interpretation and other data，the sedimentary evolution characteristics and the main controlling factors of the 2nd and 3rd members of Paleogene Shahejie Formation in downthrown side of Shicun Fault in Dongying sag were researched. The result shows that the sedimentary facies of the 3rd member of Shahejie Formation includes delta plain subfacies，delta front subfacies，shore-shallow lake subfacies and beach-bar subfacies. The southeastern Guangrao Salient and the southwestern Luxi Uplift were the two major provenances in this depositional period. The braided delta front subfacies，delta front subfacies，shore-shallow lake subfacies and beach-bar subfacies were identified in the 2nd member of Shahejie Formation. The braided delta front subfacies developed in the eastern zone of the study area，which was affected by the source supply of Guangrao Salient. The delta front subfacies originated from Luxi Uplift developed in the southern zone dominantly. The sedimentary filling process was from retrogradation to progradation during the deposition of the 3rd member and the 2nd member of Shahejie Formation. The development and evolution of sedimentary facies were mainly affected and controlled by fault movement，supply intensity of provenances and paleoclimate.
Based on well logging，drilling，seismic interpretation and other data，the sedimentary evolution characteristics and the main controlling factors of the 2nd and 3rd members of Paleogene Shahejie Formation in downthrown side of Shicun Fault in Dongying sag were researched. The result shows that the sedimentary facies of the 3rd member of Shahejie Formation includes delta plain subfacies，delta front subfacies，shore-shallow lake subfacies and beach-bar subfacies. The southeastern Guangrao Salient and the southwestern Luxi Uplift were the two major provenances in this depositional period. The braided delta front subfacies，delta front subfacies，shore-shallow lake subfacies and beach-bar subfacies were identified in the 2nd member of Shahejie Formation. The braided delta front subfacies developed in the eastern zone of the study area，which was affected by the source supply of Guangrao Salient. The delta front subfacies originated from Luxi Uplift developed in the southern zone dominantly. The sedimentary filling process was from retrogradation to progradation during the deposition of the 3rd member and the 2nd member of Shahejie Formation. The development and evolution of sedimentary facies were mainly affected and controlled by fault movement，supply intensity of provenances and paleoclimate.
2017, 24(2):30-37.
DOI: 10.13673/j.cnki.cn37-1359/te.2017.02.005
Abstract:
The sandbodies of fan delta front developed widely in Cretaceous Bashenjiqike Formation in the foreland area of Kuqa depression，which are favorable places for natural gas accumulation. In view of the situation of few drillings and large inter-well spacing in a certain gas field，a typical outcrop，which has the similar geological situation with the target stratum，was chosen to be scanned in multi-faceted and full coverage by the holographic laser scanning technology for acquiring three-dimensional data，and then a three-dimensional digital geological model was built through matching the data with the measured geological information and sampling analysis data by computer simulation technology to reveal the sandbody architecture of fan delta front effectively. The results show that the sandbody architecture types of fan delta front in the study area include three types：incomplete stacked stitching type，side stitching type and isolated type，while the sandbody connectivity are very different owing to the architecture differences. The channel sandbodies are presented as multiple underwater distributary channels stacked vertically and distributed widely，where the physical properties of the middle and lower part are better than that of the bottom and the top and the homogeneous medium sandstone and fine sandstone are the best. A few mouth bars and distal bars are also developed with a negative correlation between the sand thickness and width thickness ratio. The sandstone content of the modeling section is high and there is stable lateral distribution of mudstone interbedded with the sandbodies. The sandbodies are not fully connected with each other and the inner-and interlayer hetero? geneity is strong.
The sandbodies of fan delta front developed widely in Cretaceous Bashenjiqike Formation in the foreland area of Kuqa depression，which are favorable places for natural gas accumulation. In view of the situation of few drillings and large inter-well spacing in a certain gas field，a typical outcrop，which has the similar geological situation with the target stratum，was chosen to be scanned in multi-faceted and full coverage by the holographic laser scanning technology for acquiring three-dimensional data，and then a three-dimensional digital geological model was built through matching the data with the measured geological information and sampling analysis data by computer simulation technology to reveal the sandbody architecture of fan delta front effectively. The results show that the sandbody architecture types of fan delta front in the study area include three types：incomplete stacked stitching type，side stitching type and isolated type，while the sandbody connectivity are very different owing to the architecture differences. The channel sandbodies are presented as multiple underwater distributary channels stacked vertically and distributed widely，where the physical properties of the middle and lower part are better than that of the bottom and the top and the homogeneous medium sandstone and fine sandstone are the best. A few mouth bars and distal bars are also developed with a negative correlation between the sand thickness and width thickness ratio. The sandstone content of the modeling section is high and there is stable lateral distribution of mudstone interbedded with the sandbodies. The sandbodies are not fully connected with each other and the inner-and interlayer hetero? geneity is strong.
2017, 24(2):38-45.
DOI: 10.13673/j.cnki.cn37-1359/te.2017.02.006
Abstract:
Chang61 low resistivity oil pays are widely distributed in Triassic Yanchang Formation in Wuqi area of Ordos Basin with large reserves. However，they are often missed or misjudged using traditional identification methods due to uncertainties in their genesis. Based on actual oilfield production practice，data from well drilling，logging，well logging，experiment analysis，well testing and producing test were analyzed for genesis analysis and identification of Chang61 low resistivity oil pays using grey correlation method. The results show that the poor pore structure is the main factor of the formation of Chang61 low resistivity oil pays，and the secondary factors are high content of chlorite and ferrocalcite cements，high formation water salinity and the fine-grained rock. Meanwhile，the cross plot method，logging curve superimposition method，NMR logging method，special logging method and multi-well correlation method were developed for low resistivity oil pays identification. These methods were put into use and good effects were obtained during oilfield production.
Chang61 low resistivity oil pays are widely distributed in Triassic Yanchang Formation in Wuqi area of Ordos Basin with large reserves. However，they are often missed or misjudged using traditional identification methods due to uncertainties in their genesis. Based on actual oilfield production practice，data from well drilling，logging，well logging，experiment analysis，well testing and producing test were analyzed for genesis analysis and identification of Chang61 low resistivity oil pays using grey correlation method. The results show that the poor pore structure is the main factor of the formation of Chang61 low resistivity oil pays，and the secondary factors are high content of chlorite and ferrocalcite cements，high formation water salinity and the fine-grained rock. Meanwhile，the cross plot method，logging curve superimposition method，NMR logging method，special logging method and multi-well correlation method were developed for low resistivity oil pays identification. These methods were put into use and good effects were obtained during oilfield production.
2017, 24(2):46-51.
DOI: 10.13673/j.cnki.cn37-1359/te.2017.02.007
Abstract:
There are good biogenic gas accumulation conditions and exploration prospects in deepwater area of Rakhine Basin in Myanmar. Biogenic gas reservoirs，as unconventional natural gas reservoirs，form under very strict conditions. It is the primary issue to study the genesis of biogenic gas-source for analysis of factors of gas accumulation. It is proved by geochemistry analysis and seismic forward modeling that the seismic response created by gas chimneys，also known as biogenic gas reservoir，is obvious in Chinese exploration area of Rakhine Basin in Myanmar. Hydrocarbon source rocks of biogas is characterized by geologic features of“three high and one low，weak diagenesis”，indicating low lower organic carbon limit，low thermal maturation，low geothermal temperature environment and high deposition rate. The rock consolidation de? gree shows that it was in the earlier stage of weak diagenesis. Canyon shale，Miocene mudstones and Pliocene mudstones could provide food and material source for methane bacteria. The overlying mudstones on the Pliocene mudstones does not have the material conditions of biogas formation. It is speculated that natural gas hydrate might exist in the research area，and its stability changes with the variation of pressure and temperature caused by external factors. As a result，amounts of biogenic methane gas is expelled and entrapped to form biogenic gas reservoir. The process of gas expulsion and accumulation can be described as continuous gas generation and pressure increase-breaking pressure balance-gas leak-pressure rebalancing-gas regeneration and the second pressure increase-breaking pressure balance again-the second gas leak-pressure rebalancing.
There are good biogenic gas accumulation conditions and exploration prospects in deepwater area of Rakhine Basin in Myanmar. Biogenic gas reservoirs，as unconventional natural gas reservoirs，form under very strict conditions. It is the primary issue to study the genesis of biogenic gas-source for analysis of factors of gas accumulation. It is proved by geochemistry analysis and seismic forward modeling that the seismic response created by gas chimneys，also known as biogenic gas reservoir，is obvious in Chinese exploration area of Rakhine Basin in Myanmar. Hydrocarbon source rocks of biogas is characterized by geologic features of“three high and one low，weak diagenesis”，indicating low lower organic carbon limit，low thermal maturation，low geothermal temperature environment and high deposition rate. The rock consolidation de? gree shows that it was in the earlier stage of weak diagenesis. Canyon shale，Miocene mudstones and Pliocene mudstones could provide food and material source for methane bacteria. The overlying mudstones on the Pliocene mudstones does not have the material conditions of biogas formation. It is speculated that natural gas hydrate might exist in the research area，and its stability changes with the variation of pressure and temperature caused by external factors. As a result，amounts of biogenic methane gas is expelled and entrapped to form biogenic gas reservoir. The process of gas expulsion and accumulation can be described as continuous gas generation and pressure increase-breaking pressure balance-gas leak-pressure rebalancing-gas regeneration and the second pressure increase-breaking pressure balance again-the second gas leak-pressure rebalancing.
2017, 24(2):52-57.
DOI: 10.13673/j.cnki.cn37-1359/te.2017.02.008
Abstract:
Magnetic susceptibility logging is recognized as an efficient and eco-friendly logging method，nevertheless，which is barely used in oil and gas field fundamentally due to the imperfection of theoretical guidance and application methodology. Therefore，taking the Quaternary in Hetao basin as an example，combined with sedimentary architecture and theories of geomagnetism，relationship between magnetic susceptibility logging and geological factors was established based on core data from drilling holes of A，B and C in the study area and the measured magnetic susceptibility data from logging，and the main factors controlling response of magnetic susceptibility logging were determined. On this basis，well-logging interpretation pattern was established by combining both conventional well logging and magnetic susceptibility logging. The results manifest that the magnetic susceptibility is abnormally high when the formation has high abundance of organic matter and paramagnetic minerals，frequent occurrence of muddy-silty intercalations and drilling fluid penetration. The variation trend of magnetic susceptibility is highly consistent with the organic matter content. The maximum value of magnetic susceptibility is 137×10-5 SI in the study area，and the correlation coefficient between magnetic susceptibility and the relative content of paramagnetic minerals is 0.87. The magnetic susceptibility also has positive correlation with the scale of horizontal bedding and drilling fluid penetration. Moreover，curve φ，which represents the systematic error of magnetic susceptibility，can reflect the fluctuation of sedimentary environment and hydro-dynamic conditions. Combined with well-logging response characteristics，magnetic susceptibility logging could be widely applied in the research of sedimentation and sequence stratigraphy，evaluation of source rock，identification of clay minerals and fine reservoir description.
Magnetic susceptibility logging is recognized as an efficient and eco-friendly logging method，nevertheless，which is barely used in oil and gas field fundamentally due to the imperfection of theoretical guidance and application methodology. Therefore，taking the Quaternary in Hetao basin as an example，combined with sedimentary architecture and theories of geomagnetism，relationship between magnetic susceptibility logging and geological factors was established based on core data from drilling holes of A，B and C in the study area and the measured magnetic susceptibility data from logging，and the main factors controlling response of magnetic susceptibility logging were determined. On this basis，well-logging interpretation pattern was established by combining both conventional well logging and magnetic susceptibility logging. The results manifest that the magnetic susceptibility is abnormally high when the formation has high abundance of organic matter and paramagnetic minerals，frequent occurrence of muddy-silty intercalations and drilling fluid penetration. The variation trend of magnetic susceptibility is highly consistent with the organic matter content. The maximum value of magnetic susceptibility is 137×10-5 SI in the study area，and the correlation coefficient between magnetic susceptibility and the relative content of paramagnetic minerals is 0.87. The magnetic susceptibility also has positive correlation with the scale of horizontal bedding and drilling fluid penetration. Moreover，curve φ，which represents the systematic error of magnetic susceptibility，can reflect the fluctuation of sedimentary environment and hydro-dynamic conditions. Combined with well-logging response characteristics，magnetic susceptibility logging could be widely applied in the research of sedimentation and sequence stratigraphy，evaluation of source rock，identification of clay minerals and fine reservoir description.
2017, 24(2):58-62.
DOI: 10.13673/j.cnki.cn37-1359/te.2017.02.009
Abstract:
Emulsion surfactant flooding is a new chemical flooding method for enhanced oil recovery. Under a certain oilwater ratio condition，this type of surfactant can interact with oil and water and form water-in-oil emulsions with high viscosity，and thus the swept volume may be enlarged. The oil displacement mechanism of the emulsion surfactant is different from the traditional polymer and surfactant，and it could not be reflected by the existing numerical simulation methods and softwares. In order to accurately reflect the oil displacement characteristics of the emulsion surfactant，based on analysis of the laboratory results，the main mechanism of emulsification and viscosity increase was manifested，and the mathematical model for characterizing emulsion flow was built and the corresponding numerical simulation method was realized. The accuracy of the mathematic model and numerical simulation method was verified by the fitting result of laboratory model and the application of field model. Relationship between the enhanced oil recovery effect of emulsion surfactant flooding and the factors of emulsion particle size，permeability and heterogeneity was researched，and the effect of emulsion surfactant flooding and conventional surfactant flooding was compared. The results show that the matching relationship between median grain size of emulsion and pore throat has a great influence on the stability and viscosity of the emulsion. Compared with the conventional surfactant，the emulsion surfactant could further improve oil recovery due to better mobility control.
Emulsion surfactant flooding is a new chemical flooding method for enhanced oil recovery. Under a certain oilwater ratio condition，this type of surfactant can interact with oil and water and form water-in-oil emulsions with high viscosity，and thus the swept volume may be enlarged. The oil displacement mechanism of the emulsion surfactant is different from the traditional polymer and surfactant，and it could not be reflected by the existing numerical simulation methods and softwares. In order to accurately reflect the oil displacement characteristics of the emulsion surfactant，based on analysis of the laboratory results，the main mechanism of emulsification and viscosity increase was manifested，and the mathematical model for characterizing emulsion flow was built and the corresponding numerical simulation method was realized. The accuracy of the mathematic model and numerical simulation method was verified by the fitting result of laboratory model and the application of field model. Relationship between the enhanced oil recovery effect of emulsion surfactant flooding and the factors of emulsion particle size，permeability and heterogeneity was researched，and the effect of emulsion surfactant flooding and conventional surfactant flooding was compared. The results show that the matching relationship between median grain size of emulsion and pore throat has a great influence on the stability and viscosity of the emulsion. Compared with the conventional surfactant，the emulsion surfactant could further improve oil recovery due to better mobility control.
2017, 24(2):63-66.
DOI: 10.13673/j.cnki.cn37-1359/te.2017.02.010
Abstract:
Conglomerate reservoir，developed in the eastern No.7 district of Karamay oilfield in Xinjiang，has entered the high water content period after polymer flooding. However，it still has high potential and high value of development. SP and ASP flooding are two commonly used development models of enhanced oil recovery after polymer flooding in the conglomerate reservoir. The physical simulation experiment was carried out in the laboratory using natural core plugs. Injection pressure，water content，recovery ratio and remaining oil distribution of SP and ASP flooding after polymer flooding were analyzed. Development model after polymer flooding in the conglomerate reservoir was optimized. The experimental results show that the difference of water content and injection pressure between SP and ASP flooding was small，and the recovery ratio of ASP flooding was slightly higher than that of SP flooding. Moreover，core slice after SP or ASP flooding were observed by ultraviolet fluorescence microscopy，and the microscopic distribution type of the remaining oil was analyzed. It is found that the remaining oil after ASP flooding is mainly adsorbed in interparticle pore，which is likely to plug flow channel and hard to be driven. And the remaining oil after SP flooding is mainly adsorbed onto the surface of particles，which is less harmful to reservoir and the subsequent development. Considering the recovery ratio，construction cost and reservoir damage，SP flooding is chosen as the way to improve oil recovery after polymer flooding.
Conglomerate reservoir，developed in the eastern No.7 district of Karamay oilfield in Xinjiang，has entered the high water content period after polymer flooding. However，it still has high potential and high value of development. SP and ASP flooding are two commonly used development models of enhanced oil recovery after polymer flooding in the conglomerate reservoir. The physical simulation experiment was carried out in the laboratory using natural core plugs. Injection pressure，water content，recovery ratio and remaining oil distribution of SP and ASP flooding after polymer flooding were analyzed. Development model after polymer flooding in the conglomerate reservoir was optimized. The experimental results show that the difference of water content and injection pressure between SP and ASP flooding was small，and the recovery ratio of ASP flooding was slightly higher than that of SP flooding. Moreover，core slice after SP or ASP flooding were observed by ultraviolet fluorescence microscopy，and the microscopic distribution type of the remaining oil was analyzed. It is found that the remaining oil after ASP flooding is mainly adsorbed in interparticle pore，which is likely to plug flow channel and hard to be driven. And the remaining oil after SP flooding is mainly adsorbed onto the surface of particles，which is less harmful to reservoir and the subsequent development. Considering the recovery ratio，construction cost and reservoir damage，SP flooding is chosen as the way to improve oil recovery after polymer flooding.
2017, 24(2):67-72.
DOI: 10.13673/j.cnki.cn37-1359/te.2017.02.011
Abstract:
Large caves，water-eroded pores and cracks are the main reservoir spaces of fractured-vuggy carbonate reservoir with complicated connectivity pattern and strong heterogeneity. CO2 huff and puff and CO2 displacement are effective productive method，which can improve development effect by supplying formation energy and reducing oil viscosity through dissolved CO2 in oil. According to the field geological data，a 3D simulation physical model was designed and used in laboratory experiment to simulate the typical fractured-vuggy reservoir units，and a series of laboratory experiments were carried out to simulate CO2 huff and puff and CO2 displacement processes. The dynamics of production was analyzed. The stimulation effect of CO2 huff and puff in high and low position was researched and the recovery percentage in high or low position with CO2 huff and puff and CO2 displacement was compared. On this basis，the mechanism of gas injection and oil displacement in the fractured-vuggy reservoir was analyzed. Experimental results show that the EOR of CO2 huff and puff in high position is 16.09% higher than that in low position due to the interaction between bottom water and secondary gas cap and the advantage of well location. Taking advantage of the different controlling areas of gas，the oil recovery of CO2 huff and puff in high and low position is 8.07% and 5.01% higher than that of CO2 displacement，respectively. The effect of CO2 huff and puff is superior to that of CO2 displacement.
Large caves，water-eroded pores and cracks are the main reservoir spaces of fractured-vuggy carbonate reservoir with complicated connectivity pattern and strong heterogeneity. CO2 huff and puff and CO2 displacement are effective productive method，which can improve development effect by supplying formation energy and reducing oil viscosity through dissolved CO2 in oil. According to the field geological data，a 3D simulation physical model was designed and used in laboratory experiment to simulate the typical fractured-vuggy reservoir units，and a series of laboratory experiments were carried out to simulate CO2 huff and puff and CO2 displacement processes. The dynamics of production was analyzed. The stimulation effect of CO2 huff and puff in high and low position was researched and the recovery percentage in high or low position with CO2 huff and puff and CO2 displacement was compared. On this basis，the mechanism of gas injection and oil displacement in the fractured-vuggy reservoir was analyzed. Experimental results show that the EOR of CO2 huff and puff in high position is 16.09% higher than that in low position due to the interaction between bottom water and secondary gas cap and the advantage of well location. Taking advantage of the different controlling areas of gas，the oil recovery of CO2 huff and puff in high and low position is 8.07% and 5.01% higher than that of CO2 displacement，respectively. The effect of CO2 huff and puff is superior to that of CO2 displacement.
2017, 24(2):73-79.
DOI: 10.13673/j.cnki.cn37-1359/te.2017.02.012
Abstract:
The limited number of natural cores obtained by drilling and sampling results in great discreteness in experiment results of indoor physical and mechanical tests. Reservoir rock mechanical parameters are hard to be determined accurately.Therefore，according to physical mechanical experiment results of cores and reservoir porosity at various burial depths interpreted by logging data in certain oilfield，a finite element analysis software RFPA2D was applied to build corresponding numerical simulation cores using numerical simulation method. The Young’s modulus，stress peak strength，residual stress strength，Poisson’s ratio and other rock mechanical parameters of cores with different porosities were analyzed. Regression analysis was done on the physical and mechanical experiment result and numerical simulation results. A prediction model was built with porosity as the main variable. Based on the prediction model，three-dimensional hydraulic fracturing model of the reservoir in certain oilfield was built and the configurations of the features were discussed. The fracturing curves predicted by the numerical simulation and those from the field operation were compared. It is shown that there is a good agreement between the simulation result of fracturing pressure and the actual one and there are few differences between the two in initiation pressure and propagation pressure of the fractured interval. The results and the method are rational and available.
The limited number of natural cores obtained by drilling and sampling results in great discreteness in experiment results of indoor physical and mechanical tests. Reservoir rock mechanical parameters are hard to be determined accurately.Therefore，according to physical mechanical experiment results of cores and reservoir porosity at various burial depths interpreted by logging data in certain oilfield，a finite element analysis software RFPA2D was applied to build corresponding numerical simulation cores using numerical simulation method. The Young’s modulus，stress peak strength，residual stress strength，Poisson’s ratio and other rock mechanical parameters of cores with different porosities were analyzed. Regression analysis was done on the physical and mechanical experiment result and numerical simulation results. A prediction model was built with porosity as the main variable. Based on the prediction model，three-dimensional hydraulic fracturing model of the reservoir in certain oilfield was built and the configurations of the features were discussed. The fracturing curves predicted by the numerical simulation and those from the field operation were compared. It is shown that there is a good agreement between the simulation result of fracturing pressure and the actual one and there are few differences between the two in initiation pressure and propagation pressure of the fractured interval. The results and the method are rational and available.
13 Study on oil displacement performance of self-assembled small-molecule supramolecular system for EOR
2017, 24(2):80-84.
DOI: 10.13673/j.cnki.cn37-1359/te.2017.02.013
Abstract:
Due to high temperature and high salinity in type-Ⅲreservoirs of Shengli oilfield，conventional polyacrylamide oil displacement agent cannot effectively enhance oil recovery. Therefore，a new type of non polyacrylamide supramolecular system with temperature resistance and salt tolerance was developed with self-made supramolecular main agent and assistant agent. And the basic performance，oil displacement efficiency and microscopic accumulation morphology were characterized. The result shows that the supramolecular system can form dense network aggregate like HPAM by self-assembly between small molecules. Under the condition of type-Ⅲreservoirs in Shengli oilfield，the viscosity of the supramolecular system increases by more than one time with mass concentration of 0.1%-0.25% compared with HPAM. Without oxygen re? moval，the viscosity of the supramolecular system keeps stable within 30 days. Single pipe physical simulation may enhance oil recovery by over 18% when the mass concentration of supramolecular system is 0.15%. So the supramolecular system is a very promising new type of oil displacement，suitable for high temperature and high salinity reservoirs in Shengli oilfield.
Due to high temperature and high salinity in type-Ⅲreservoirs of Shengli oilfield，conventional polyacrylamide oil displacement agent cannot effectively enhance oil recovery. Therefore，a new type of non polyacrylamide supramolecular system with temperature resistance and salt tolerance was developed with self-made supramolecular main agent and assistant agent. And the basic performance，oil displacement efficiency and microscopic accumulation morphology were characterized. The result shows that the supramolecular system can form dense network aggregate like HPAM by self-assembly between small molecules. Under the condition of type-Ⅲreservoirs in Shengli oilfield，the viscosity of the supramolecular system increases by more than one time with mass concentration of 0.1%-0.25% compared with HPAM. Without oxygen re? moval，the viscosity of the supramolecular system keeps stable within 30 days. Single pipe physical simulation may enhance oil recovery by over 18% when the mass concentration of supramolecular system is 0.15%. So the supramolecular system is a very promising new type of oil displacement，suitable for high temperature and high salinity reservoirs in Shengli oilfield.
2017, 24(2):85-89.
DOI: 10.13673/j.cnki.cn37-1359/te.2017.02.014
Abstract:
Anaerobic microbial degradation of crude oil is the main reason of the formation of heavy oil reservoir and associated gas reservoir. In order to study the formation process of heavy oil and associated gas by anaerobic microbial degradation of crude oil，shallow gas and heavy oil in Linfanjia area were studied. The heavy oil generated from the same source rock was selected for biodegradation experiment using oil-degrading bacterial consortium of the anaerobic microbe. It was found that the thin oil could be biodegraded and transformed to heavy oil，and at the same time 3 mmol methane and 0.5 mmol carbon dioxide could be produced per gram of crude oil on average after 248 days of degradation. The analysis on the produced gas carbon isotopes indicates that the δ13C1 of CH4 ranges from -46.36‰ to -45.27‰ and the δ13C1 of CO2 ranges from 4.24‰ to 8.5‰. Biodegradation gas in shallow gas of Linfanjia area accounts for 69% based on calculation result of carbon isotope data. The content of saturated hydrocarbon in crude oil was greatly reduced from 72.77% to 44.0%，which is the main reason of crude oil densification. Biomarker 25-norhopane/hopance significantly rose from 0.009 to 0.056，which indicates that the oil has suffered serious biodegradation. The process of crude oil biodegradation can be simulated in laboratory with shorter time.
Anaerobic microbial degradation of crude oil is the main reason of the formation of heavy oil reservoir and associated gas reservoir. In order to study the formation process of heavy oil and associated gas by anaerobic microbial degradation of crude oil，shallow gas and heavy oil in Linfanjia area were studied. The heavy oil generated from the same source rock was selected for biodegradation experiment using oil-degrading bacterial consortium of the anaerobic microbe. It was found that the thin oil could be biodegraded and transformed to heavy oil，and at the same time 3 mmol methane and 0.5 mmol carbon dioxide could be produced per gram of crude oil on average after 248 days of degradation. The analysis on the produced gas carbon isotopes indicates that the δ13C1 of CH4 ranges from -46.36‰ to -45.27‰ and the δ13C1 of CO2 ranges from 4.24‰ to 8.5‰. Biodegradation gas in shallow gas of Linfanjia area accounts for 69% based on calculation result of carbon isotope data. The content of saturated hydrocarbon in crude oil was greatly reduced from 72.77% to 44.0%，which is the main reason of crude oil densification. Biomarker 25-norhopane/hopance significantly rose from 0.009 to 0.056，which indicates that the oil has suffered serious biodegradation. The process of crude oil biodegradation can be simulated in laboratory with shorter time.
2017, 24(2):90-94.
DOI: 10.13673/j.cnki.cn37-1359/te.2017.02.015
Abstract:
The remaining economic recoverable reserves are the core assets of oil companies. Their scales and value reflect the development potential of the company，which directly affects the depreciation and profit of the company and value retaining and increment of oil and gas assets. Based on the calculation model of the remaining economic recoverable reserves and the reserve value，sensitivity of initial oil production，decline rate，oil price and operation cost under different oil prices on the remaining economic recoverable reserves and reserve value are determined quantitatively. The results show that the remaining economic recoverable reserves and reserve value are positively correlated with oil price and initial oil production，and negatively correlated with decline rate and operation cost. Under different oil prices，the remaining economic recoverable reserves and reserve value have different sensitivities to various factors. At high oil price，the main influencing factors are initial oil production and decline rate. With the declining of oil price，the influences of oil price and operation cost on the remaining economic recoverable reserves and reserve value are gradually enhanced，and even exceed those of the initial production and decline rate at a certain oil price.
The remaining economic recoverable reserves are the core assets of oil companies. Their scales and value reflect the development potential of the company，which directly affects the depreciation and profit of the company and value retaining and increment of oil and gas assets. Based on the calculation model of the remaining economic recoverable reserves and the reserve value，sensitivity of initial oil production，decline rate，oil price and operation cost under different oil prices on the remaining economic recoverable reserves and reserve value are determined quantitatively. The results show that the remaining economic recoverable reserves and reserve value are positively correlated with oil price and initial oil production，and negatively correlated with decline rate and operation cost. Under different oil prices，the remaining economic recoverable reserves and reserve value have different sensitivities to various factors. At high oil price，the main influencing factors are initial oil production and decline rate. With the declining of oil price，the influences of oil price and operation cost on the remaining economic recoverable reserves and reserve value are gradually enhanced，and even exceed those of the initial production and decline rate at a certain oil price.
2017, 24(2):95-100.
DOI: 10.13673/j.cnki.cn37-1359/te.2017.02.016
Abstract:
In order to analyze the effect of different types of injected water on reservoir seepage ability，core samples in H oilfield of Middle East was prepared to simulate formation water and injected water seepage experiments of single phase and oil-water two phase were made. The experiment results were comparatively analyzed and described by mathematical model. The results show that：the scouring effect of injected water A results in loss of solid particles and mineral compositions from core samples，which leads to stronger seepage ability of the core samples. So oil absolute permeability，water absolute permeability and the sum of oil and water absolute permeability are increased. The lipophilicity of the core samples is weakened and the hydrophilicity is enhanced. The residual oil saturation is reduced and the equivalent permeability point shifts to the right. Compared with the result of simulated formation water displacement，the oil displacement efficiency is increased by 2% to 5%. Mathematical model based on the experimental results can give more accurate description on oilwater seepage rule in early，middle and late stages of oilfield exploitation.
In order to analyze the effect of different types of injected water on reservoir seepage ability，core samples in H oilfield of Middle East was prepared to simulate formation water and injected water seepage experiments of single phase and oil-water two phase were made. The experiment results were comparatively analyzed and described by mathematical model. The results show that：the scouring effect of injected water A results in loss of solid particles and mineral compositions from core samples，which leads to stronger seepage ability of the core samples. So oil absolute permeability，water absolute permeability and the sum of oil and water absolute permeability are increased. The lipophilicity of the core samples is weakened and the hydrophilicity is enhanced. The residual oil saturation is reduced and the equivalent permeability point shifts to the right. Compared with the result of simulated formation water displacement，the oil displacement efficiency is increased by 2% to 5%. Mathematical model based on the experimental results can give more accurate description on oilwater seepage rule in early，middle and late stages of oilfield exploitation.
2017, 24(2):101-106.
DOI: 10.13673/j.cnki.cn37-1359/te.2017.02.017
Abstract:
The determination of interwell permeability can be used to reservoir description and plane heterogeneity evaluation，which is of vital importance to the oilfield development decision making. The conventional approach for calculating interwell permeability is dynamic testing method. Because of the complex operation process and excessive cost，its application has been limited. To solve this problem，the relationship between interwell permeability and injection allocation coefficients was established based on hydropower similarity principle. Combined with Capacitance-Resistance Model（CRM）that enables estimation of injection allocation coefficients，a novel method was proposed for calculating the interwell permeability using injection and production data. The method was validated by numerical conceptual models，and was further applied to E07 well group in south Bozhong 25 oilfield. The results show that the estimated interwell permeability in direction of oil well E18 reaches the maximum value，which matches the fastest frontal movement of waterflood in that direction by tracer testing. In addition，the estimated value 5 192×10-3 μm2 in E18 direction is basically consistent with the interpretation value 5 616×10- 3 μm2 by tracer testing. The method extends the application range of CRM from injection allocation coefficients estimation to interwell permeability estimation，which provides a rapid and efficient tool for reservoir plane heterogeneity research.
The determination of interwell permeability can be used to reservoir description and plane heterogeneity evaluation，which is of vital importance to the oilfield development decision making. The conventional approach for calculating interwell permeability is dynamic testing method. Because of the complex operation process and excessive cost，its application has been limited. To solve this problem，the relationship between interwell permeability and injection allocation coefficients was established based on hydropower similarity principle. Combined with Capacitance-Resistance Model（CRM）that enables estimation of injection allocation coefficients，a novel method was proposed for calculating the interwell permeability using injection and production data. The method was validated by numerical conceptual models，and was further applied to E07 well group in south Bozhong 25 oilfield. The results show that the estimated interwell permeability in direction of oil well E18 reaches the maximum value，which matches the fastest frontal movement of waterflood in that direction by tracer testing. In addition，the estimated value 5 192×10-3 μm2 in E18 direction is basically consistent with the interpretation value 5 616×10- 3 μm2 by tracer testing. The method extends the application range of CRM from injection allocation coefficients estimation to interwell permeability estimation，which provides a rapid and efficient tool for reservoir plane heterogeneity research.
2017, 24(2):107-110.
DOI: 10.13673/j.cnki.cn37-1359/te.2017.02.018
Abstract:
Suizhong oilfield is an offshore heavy oil one. The ground density of crude oil is between 0.958 and 0.982 g/cm3.The underground viscosity of crude oil is between 50 and 250 mPa?s. In order to decrease water breakthrough，to enhance oil recovery and to improve development effect，polymer flooding pilot test was put into practice in 2003. Enhanced liquid treatment was implemented fully in high water cut block in 2010，and subdivision of layer series was put into practice in 2013. With the implementation of various measures，it is difficult to distinguish incremental oil effect of each measure.Analogy method was used to evaluate polymer flooding effect. The new water cut forecasting model was derived based on relative permeability curve and material balance theory. By comparing the predicted water cut curve with the actual water cut curve，the turning point of the curve is response time，and the difference value of the curve is oil increment of polymer flooding. Incremental oil of various measures was calculated by dynamic method and numerical simulation method，which realizes the splitting of incremental oil from polymer flooding，integral liquid increase，subdivision of series of strata and other stimulation measures. By the end of 2015，the cumulative incremental oil of polymer flooding is 264.3×104 m3，that of integral liquid increase is 97.1×104 m3，and that of subdivision of series of strata is 12.6×104 m3.
Suizhong oilfield is an offshore heavy oil one. The ground density of crude oil is between 0.958 and 0.982 g/cm3.The underground viscosity of crude oil is between 50 and 250 mPa?s. In order to decrease water breakthrough，to enhance oil recovery and to improve development effect，polymer flooding pilot test was put into practice in 2003. Enhanced liquid treatment was implemented fully in high water cut block in 2010，and subdivision of layer series was put into practice in 2013. With the implementation of various measures，it is difficult to distinguish incremental oil effect of each measure.Analogy method was used to evaluate polymer flooding effect. The new water cut forecasting model was derived based on relative permeability curve and material balance theory. By comparing the predicted water cut curve with the actual water cut curve，the turning point of the curve is response time，and the difference value of the curve is oil increment of polymer flooding. Incremental oil of various measures was calculated by dynamic method and numerical simulation method，which realizes the splitting of incremental oil from polymer flooding，integral liquid increase，subdivision of series of strata and other stimulation measures. By the end of 2015，the cumulative incremental oil of polymer flooding is 264.3×104 m3，that of integral liquid increase is 97.1×104 m3，and that of subdivision of series of strata is 12.6×104 m3.
2017, 24(2):111-115.
DOI: 10.13673/j.cnki.cn37-1359/te.2017.02.019
Abstract:
Reservoir protection is an essential condition for economical and efficient exploration of the tight sandstone gas reservoirs. Now，the main method to evaluate the reservoir protection effect of the drilling fluid is permeability recovery，but it is so simple that cannot evaluate the long-term impact of drilling fluid on the gas reservoir productivity，which is a process of long-term interaction between two phases of gas and fluid. While the relative permeability experiment of the core before and after being polluted by the drilling fluid can be a good remedy for the problem. According to the reservoir characteristics of the Shenmu block in Tarim oilfield，comprehensive analysis and comparison were done on the variation of core permeability recovery value，relative permeability curves and oil and water saturation used in sandstone module of CMG numerical simulation software before and after pollution of core by polysulfonated potassium drilling fluid and oil-based drilling fluid. Reservoir protection effect of the polysulfonated potassium drilling fluid and oil-based drilling fluid was simulated. The impact of various drilling fluids on the gas reservoir productivity was matched and the productivity can be an evaluation index of formation damage degree. The comprehensive evaluation results show that the oil-based drilling fluid has a better effect of reservoir protection than the polysulfonated potassium drilling fluid. The cumulative gas production will be increased by 15%.
Reservoir protection is an essential condition for economical and efficient exploration of the tight sandstone gas reservoirs. Now，the main method to evaluate the reservoir protection effect of the drilling fluid is permeability recovery，but it is so simple that cannot evaluate the long-term impact of drilling fluid on the gas reservoir productivity，which is a process of long-term interaction between two phases of gas and fluid. While the relative permeability experiment of the core before and after being polluted by the drilling fluid can be a good remedy for the problem. According to the reservoir characteristics of the Shenmu block in Tarim oilfield，comprehensive analysis and comparison were done on the variation of core permeability recovery value，relative permeability curves and oil and water saturation used in sandstone module of CMG numerical simulation software before and after pollution of core by polysulfonated potassium drilling fluid and oil-based drilling fluid. Reservoir protection effect of the polysulfonated potassium drilling fluid and oil-based drilling fluid was simulated. The impact of various drilling fluids on the gas reservoir productivity was matched and the productivity can be an evaluation index of formation damage degree. The comprehensive evaluation results show that the oil-based drilling fluid has a better effect of reservoir protection than the polysulfonated potassium drilling fluid. The cumulative gas production will be increased by 15%.
20 Effect of injected water properties on oil displacement effect in Middle East carbonate reservoirs
2017, 24(2):116-120.
DOI: 10.13673/j.cnki.cn37-1359/te.2017.02.020
Abstract:
Carbonate reservoirs in Middle East are mainly porous. Water flooding will be a useful development scheme，and water flooding recovery is influenced by properties of injected water. Based on the core displacement experiments of carbonate reservoir in M layer of Middle East，effects of salinity and mass concentration of calcium ion and sulfate ion of the injected water on oil displacement were studied. The results show that water flooding recovery can be effectively enhanced and oil displacement can be effectively improved when the salinity and calcium ion concentration of injected water decrease and sulfate ion concentration of injected water increases. The oil displacement effect may be enhanced through the change of salinity and ion mass concentration of the injected water in the process of water flooding in the field. The experiment results can be used for guiding optimal selection and improving the source of injected water of carbonate reservoir in M layer of Middle East.
Carbonate reservoirs in Middle East are mainly porous. Water flooding will be a useful development scheme，and water flooding recovery is influenced by properties of injected water. Based on the core displacement experiments of carbonate reservoir in M layer of Middle East，effects of salinity and mass concentration of calcium ion and sulfate ion of the injected water on oil displacement were studied. The results show that water flooding recovery can be effectively enhanced and oil displacement can be effectively improved when the salinity and calcium ion concentration of injected water decrease and sulfate ion concentration of injected water increases. The oil displacement effect may be enhanced through the change of salinity and ion mass concentration of the injected water in the process of water flooding in the field. The experiment results can be used for guiding optimal selection and improving the source of injected water of carbonate reservoir in M layer of Middle East.
2017, 24(2):121-126.
Abstract:
Beach-bar sandstone reservoirs are characterized by large longitudinal span，multiple thin layers，poor physical properties and strong heterogeneity. Traditional integral fracturing has poor effect. Step-by-step fracturing costs high with complex operation. Optimization of the separate layer fracturing technology has crucial significance on production. Aimed at the difficulty about low degree of longitudinal stimulation，lacking of effective fracture length and flow conductivity，the beach-bar sandstone reservoirs in Dongying sag were researched. First，in-situ stress profile was determined，concentrated perforation and critical discharge capacity in various layers was optimized. Fracture parameters of the vertical fracturing were optimized. The degree of longitudinal stimulation of long-section and multi-thin-layer reservoir was improved using separate layer fracturing. Second，the effective placement of proppant was realized and the degree of layer stimulation was improved by optimizing the fracture parameters，operation parameters，proppant and low-damage fracturing fluid system.The application result of separate layer fracturing in Bin 438 well block show that the average oil production after three months of the separate layer fracturing is 2.2 times of that of the integral fracturing in adjacent wells，which demonstratesthe effectiveness of this method.
Beach-bar sandstone reservoirs are characterized by large longitudinal span，multiple thin layers，poor physical properties and strong heterogeneity. Traditional integral fracturing has poor effect. Step-by-step fracturing costs high with complex operation. Optimization of the separate layer fracturing technology has crucial significance on production. Aimed at the difficulty about low degree of longitudinal stimulation，lacking of effective fracture length and flow conductivity，the beach-bar sandstone reservoirs in Dongying sag were researched. First，in-situ stress profile was determined，concentrated perforation and critical discharge capacity in various layers was optimized. Fracture parameters of the vertical fracturing were optimized. The degree of longitudinal stimulation of long-section and multi-thin-layer reservoir was improved using separate layer fracturing. Second，the effective placement of proppant was realized and the degree of layer stimulation was improved by optimizing the fracture parameters，operation parameters，proppant and low-damage fracturing fluid system.The application result of separate layer fracturing in Bin 438 well block show that the average oil production after three months of the separate layer fracturing is 2.2 times of that of the integral fracturing in adjacent wells，which demonstratesthe effectiveness of this method.
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