Volume 22,Issue 4,2015 Table of Contents
1 Research on geothermal resources assessment of the Guantao-Dongying Formation in Jiyang depression
2015, 22(4):1-5.
Abstract:
Geothermal resource is a kind of renewable clean energy which is significant to promote energy-saving and emission-reduction and green and low carbon. On the basis of regional geological characteristics analysis and the research on geothermal reservoir and geothermal field，the geothermal reservoirs of the Dongying Formation and the lower Guantao Formation in Jiyang depression were divided into 12 geothermal units as quick heat supply type，26 geothermal units as moderate-speed heat supply type and 33 geothermal units as low-speed heat supply type. The geothermal reservoir conceptual model was set up combining with comprehensive analysis of pressure and hydrochemical field. The geothermal reservoirs develop in deltas and braided rivers of the Dongying Formation and the lower Guantao Formation. The crust mantle heat flow，formed during the evolution of faulted basin，conducts to the upper geothermal reservoirs and is stored along bedrock under the blocking of thick mudstones and loose insulating layers developing in the Minghuazhen-Quaternary Formation.There is no surface seepage or air infiltration in the geothermal reservoirs. And it is infinite confined horizontal two-dimen? sional flow without inter layer leakage flow for outward heat leaking. The heat storage method was selected to calculate the resource and the results show that the geothermal resources of the lower Guantao Formation and the Dongying Formation are 419.18×109 GJ，which amount to 143.12 million tons of standard coal. The recoverable geothermal resources are 104.8×109 GJ，which amount to 35.8 million tons of standard coal.
Geothermal resource is a kind of renewable clean energy which is significant to promote energy-saving and emission-reduction and green and low carbon. On the basis of regional geological characteristics analysis and the research on geothermal reservoir and geothermal field，the geothermal reservoirs of the Dongying Formation and the lower Guantao Formation in Jiyang depression were divided into 12 geothermal units as quick heat supply type，26 geothermal units as moderate-speed heat supply type and 33 geothermal units as low-speed heat supply type. The geothermal reservoir conceptual model was set up combining with comprehensive analysis of pressure and hydrochemical field. The geothermal reservoirs develop in deltas and braided rivers of the Dongying Formation and the lower Guantao Formation. The crust mantle heat flow，formed during the evolution of faulted basin，conducts to the upper geothermal reservoirs and is stored along bedrock under the blocking of thick mudstones and loose insulating layers developing in the Minghuazhen-Quaternary Formation.There is no surface seepage or air infiltration in the geothermal reservoirs. And it is infinite confined horizontal two-dimen? sional flow without inter layer leakage flow for outward heat leaking. The heat storage method was selected to calculate the resource and the results show that the geothermal resources of the lower Guantao Formation and the Dongying Formation are 419.18×109 GJ，which amount to 143.12 million tons of standard coal. The recoverable geothermal resources are 104.8×109 GJ，which amount to 35.8 million tons of standard coal.
2015, 22(4):6-13.
Abstract:
The 3D basin modeling technique was used to restore the geohistory evolution process of Middle-Upper Yangtze area. Based on geological development characteristics，the control of paleo-tectonic on sedimentary was analyzed to point out its geological significance for hydrocarbon generation. The results show that depressions and uplifts developed alternately in the Yangtze area before Devonian sedimentary period，and an uplift and two depressions of north-east striking developed in Yangtze platform during Indo-Chinese epoch. Through comparing the structures developed in the Caledonian period and in Indo-Chinese epoch，Chuanxi depression developed in Indo-Chinese epoch locates on the Leshan-Longnüsi uplift developed in the Caledonian period. Luzhou paleo-uplift developed in Indo-Chinese epoch superposes on the Chuannan depression developed in the Caledonian period. The zone of Nanchong-Liangping locates in structure transform regions and the Shishou-Yichang uplift develops in north depression of Jianghan Basin，which suggests that the Caledonian strata reversed strongly in Indo-Chinese epoch. The Caledonian structures superposed and reversed strongly in Indo-Chinese ep? och showing by the east-west and the north-south structural evolution profiles crossing the whole Sichuan Basin.The Luzhou paleo-uplift，superposed on the Caledonian paleo-depression developed in Indo-Chinese epoch，is a typical uplift which could accumulate hydrocarbons generated from the Silurian source rocks below. It could form favorable reservoirs and has good exploration prospect. The Leshan-Longnüsi paleo-uplift and the Qianzhong paleo-uplift are the areas that receive the charge of hydrocarbons coming from the source rocks below until the Indo-Chinese epoch，but they only control the accumulation of the Cambrian hydrocarbons underlying the Ordovician. The paleo-slope adjacent to the hydrocarbon generation depression of the Cambrian source rocks is the benefit zone for hydrocarbon exploration.
The 3D basin modeling technique was used to restore the geohistory evolution process of Middle-Upper Yangtze area. Based on geological development characteristics，the control of paleo-tectonic on sedimentary was analyzed to point out its geological significance for hydrocarbon generation. The results show that depressions and uplifts developed alternately in the Yangtze area before Devonian sedimentary period，and an uplift and two depressions of north-east striking developed in Yangtze platform during Indo-Chinese epoch. Through comparing the structures developed in the Caledonian period and in Indo-Chinese epoch，Chuanxi depression developed in Indo-Chinese epoch locates on the Leshan-Longnüsi uplift developed in the Caledonian period. Luzhou paleo-uplift developed in Indo-Chinese epoch superposes on the Chuannan depression developed in the Caledonian period. The zone of Nanchong-Liangping locates in structure transform regions and the Shishou-Yichang uplift develops in north depression of Jianghan Basin，which suggests that the Caledonian strata reversed strongly in Indo-Chinese epoch. The Caledonian structures superposed and reversed strongly in Indo-Chinese ep? och showing by the east-west and the north-south structural evolution profiles crossing the whole Sichuan Basin.The Luzhou paleo-uplift，superposed on the Caledonian paleo-depression developed in Indo-Chinese epoch，is a typical uplift which could accumulate hydrocarbons generated from the Silurian source rocks below. It could form favorable reservoirs and has good exploration prospect. The Leshan-Longnüsi paleo-uplift and the Qianzhong paleo-uplift are the areas that receive the charge of hydrocarbons coming from the source rocks below until the Indo-Chinese epoch，but they only control the accumulation of the Cambrian hydrocarbons underlying the Ordovician. The paleo-slope adjacent to the hydrocarbon generation depression of the Cambrian source rocks is the benefit zone for hydrocarbon exploration.
2015, 22(4):14-19.
Abstract:
Based on comprehensive analysis of the present exploration research，the tecto-sedimentary evolution features of the deep-water pre-salt in Gabon basin and its effect on hydrocarbon accumulation were studied to reveal the hydrocarbon accumulation conditions and key factors and to guide the hydrocarbon exploration in the area effectively. The results show that the pre-salt in Gabon basin experienced three tecto-sedimentary evolution stages：the faulting stage（early Cretaceous Neocomian-early Barremian），the faulting-downwarping stage（late Barremian-early Aptian）and early basin transition stage（middle Aptian）. Pre-salt lacustrine source rocks developed during the faulting stage. Influenced by the strong basin rifting in the south and the weak basin rifting in the north，the pre-salt lacustrine source rocks in the sub-basin of north Gabon developed only within the rifting belt，while those in the sub-basin of south Gabon distributed widely. The different distribution of source rocks is the main reason that the deep-water pre-salt hydrocarbon discoveries success in the sub-basin of south Gabon but failed in the sub basin of north Gabon. The main pre-salt reservoirs developed during the faultingdownwarping and the early basin transition stage. Due to the inherited effects of outward migration of subsidence center from the rift belt and strong subsidence in the south and weak subsidence in the north，the fluvial deposits widely developed in the inner rift belt and the central uplift belt in the Dentale Formation during the faulting-downwarping stage，while the deltaic front-shallow lacustrine deposits developed in the outer rift belt（deep-water sub-basin in south Gabon）.In the ear? ly basin transition stage，the Gamba Formation deposited under a peneplain setting；the fluvial-deltaic plain deposits developed in the inner rift belt and central uplift belt，and the deltaic front-shallow lacustrine deposits developed in the outer rift belt（present deep-water area），both of which are at risk of reservoir properties deteriorated toward deep-water area. The long-distance provenance migration along the N’Komi Fracture Zone might play a positive role in the development of Gam? ba and Dentale reservoirs in the deep-water outer rift belt.
Based on comprehensive analysis of the present exploration research，the tecto-sedimentary evolution features of the deep-water pre-salt in Gabon basin and its effect on hydrocarbon accumulation were studied to reveal the hydrocarbon accumulation conditions and key factors and to guide the hydrocarbon exploration in the area effectively. The results show that the pre-salt in Gabon basin experienced three tecto-sedimentary evolution stages：the faulting stage（early Cretaceous Neocomian-early Barremian），the faulting-downwarping stage（late Barremian-early Aptian）and early basin transition stage（middle Aptian）. Pre-salt lacustrine source rocks developed during the faulting stage. Influenced by the strong basin rifting in the south and the weak basin rifting in the north，the pre-salt lacustrine source rocks in the sub-basin of north Gabon developed only within the rifting belt，while those in the sub-basin of south Gabon distributed widely. The different distribution of source rocks is the main reason that the deep-water pre-salt hydrocarbon discoveries success in the sub-basin of south Gabon but failed in the sub basin of north Gabon. The main pre-salt reservoirs developed during the faultingdownwarping and the early basin transition stage. Due to the inherited effects of outward migration of subsidence center from the rift belt and strong subsidence in the south and weak subsidence in the north，the fluvial deposits widely developed in the inner rift belt and the central uplift belt in the Dentale Formation during the faulting-downwarping stage，while the deltaic front-shallow lacustrine deposits developed in the outer rift belt（deep-water sub-basin in south Gabon）.In the ear? ly basin transition stage，the Gamba Formation deposited under a peneplain setting；the fluvial-deltaic plain deposits developed in the inner rift belt and central uplift belt，and the deltaic front-shallow lacustrine deposits developed in the outer rift belt（present deep-water area），both of which are at risk of reservoir properties deteriorated toward deep-water area. The long-distance provenance migration along the N’Komi Fracture Zone might play a positive role in the development of Gam? ba and Dentale reservoirs in the deep-water outer rift belt.
Wang Yong
,
Song Guoqi
,
Liu Huimin
,
Jiang Xiufang
,
Hao Xuefeng
,
Ning Fangxing
,
Zhu Deshun
,
Lin Lu
2015, 22(4):20-25.
Abstract:
Based on shale oil reservoir types，effective single layer thickness distribution of conventional oil and gas in the area with proved reserves，and thickness distribution and proportion of interbed in wells drilling at shale oil，the shale oil enrichment types in Jiyang depression are divided into matrix，fracture and interbed with a thickness not more than 2.5 m and a proportion not more than 20%. By typical well analyzing and mathematical statistics，factors for shale oil enrichment were analyzed. Enrichment factors of the matrix type include lithofacies，reservoir performance，abnormal pressures and shale oil mobility. Organic-rich layered muddy limestone and organic-rich lime mudstone are the most favorable lithofacies. The porosity of oil charging segment is more than 3%. And there is a significant positive correlation between reservoir properties and the daily outputs. The low-pressure area among abnormal high pressure areas is relatively enriched in shale oil. The mobility of shale oil is good while S1/ TOC >1. Enrichment factors of the fractured type include lithofacies，fracture development extent and fault sealing，and the layered lithofacies is easy to form net fracture and controls vertical distribution of fracture-type shale oil. Fractures develop when fracture development coefficient is more than 0.2. High-yield wells distribute in hanging wall of fault where the distance between well and fault is less than 1.2 km and fault throw is more than 100 m. Shale oil enriches in abnormal high pressure area（pressure coefficient>1.3）which is in good preservation conditions.Enrichment factors of the interbed type include reservoir property，source rock expulsion intensity and abnormal pressure.
Based on shale oil reservoir types，effective single layer thickness distribution of conventional oil and gas in the area with proved reserves，and thickness distribution and proportion of interbed in wells drilling at shale oil，the shale oil enrichment types in Jiyang depression are divided into matrix，fracture and interbed with a thickness not more than 2.5 m and a proportion not more than 20%. By typical well analyzing and mathematical statistics，factors for shale oil enrichment were analyzed. Enrichment factors of the matrix type include lithofacies，reservoir performance，abnormal pressures and shale oil mobility. Organic-rich layered muddy limestone and organic-rich lime mudstone are the most favorable lithofacies. The porosity of oil charging segment is more than 3%. And there is a significant positive correlation between reservoir properties and the daily outputs. The low-pressure area among abnormal high pressure areas is relatively enriched in shale oil. The mobility of shale oil is good while S1/ TOC >1. Enrichment factors of the fractured type include lithofacies，fracture development extent and fault sealing，and the layered lithofacies is easy to form net fracture and controls vertical distribution of fracture-type shale oil. Fractures develop when fracture development coefficient is more than 0.2. High-yield wells distribute in hanging wall of fault where the distance between well and fault is less than 1.2 km and fault throw is more than 100 m. Shale oil enriches in abnormal high pressure area（pressure coefficient>1.3）which is in good preservation conditions.Enrichment factors of the interbed type include reservoir property，source rock expulsion intensity and abnormal pressure.
2015, 22(4):26-32.
Abstract:
Based on the approach of tectonic-sedimentary analysis and the basin tectonic activity，the filling response of paleogene tectonic-sedimentary and its evolution process in great details were studied by 3D seismic and drilling data of the Shabei area in Bozhong depression. Furthermore，combined with the corresponding relationship among the lithofacies，seismic facies and seismic attributes，the tectonic-sedimentary evolution regularity in time-space was discussed. Five types of ancient valley systems（U-type，W-type，V-type valleys，single fault trough，and double fault trough），and four types of tectonic break zones（cliff type，ramp type，synthetic and antithetic fault terrace types）developed in the study area. The sandtransport ability of different ancient valleys varies，so the scale of its corresponding fan body differs as well；sedimentary build-up varies with different slope broken zones. The sand-rich fan delta and mud-rich coastal shallow-lake developed during Shahejie Formation deposited in the study region，whose provenance came from the near source system of Shijiutuo uplift and Shaleitian uplift. However，not only the fan delta developed during Dongying Formation sedimentary period，but also the braided river delta began to develop，which included two main provenance systems（the near source system of Shijiutuo uplift and Shaleitian uplift）and the far source system of northern paleo-Luan River.
Based on the approach of tectonic-sedimentary analysis and the basin tectonic activity，the filling response of paleogene tectonic-sedimentary and its evolution process in great details were studied by 3D seismic and drilling data of the Shabei area in Bozhong depression. Furthermore，combined with the corresponding relationship among the lithofacies，seismic facies and seismic attributes，the tectonic-sedimentary evolution regularity in time-space was discussed. Five types of ancient valley systems（U-type，W-type，V-type valleys，single fault trough，and double fault trough），and four types of tectonic break zones（cliff type，ramp type，synthetic and antithetic fault terrace types）developed in the study area. The sandtransport ability of different ancient valleys varies，so the scale of its corresponding fan body differs as well；sedimentary build-up varies with different slope broken zones. The sand-rich fan delta and mud-rich coastal shallow-lake developed during Shahejie Formation deposited in the study region，whose provenance came from the near source system of Shijiutuo uplift and Shaleitian uplift. However，not only the fan delta developed during Dongying Formation sedimentary period，but also the braided river delta began to develop，which included two main provenance systems（the near source system of Shijiutuo uplift and Shaleitian uplift）and the far source system of northern paleo-Luan River.
2015, 22(4):33-37.
Abstract:
To establish different levels of reservoir architectures of the braided river sedimentary system for adjustment and remaining oil exploration，based on the hierarchical level system of fluvial facies，the architecture interfaces of braided river reservoir in Ying-13 fault block can be classified into six hierarchies，and the causes and distribution characteristics of 3-6 hierarchy architecture interfaces were determined. According to different levels of architecture interfaces，based on sequence stratigraphy，analysis of spatial stacking pattern of channel sand-body，classification of architectural element，internal anatomy of mid-channel bar，etc.，the architecture model of the braided river have been categorized into four different levels，from large to small in turn which are complex braided river sand-body，fluvial sand-body，internal sand-body and internal mid-beach bar. Four-different stages channel complex sand-bodies developed in Dong2 oil bed of Ying-13 fault block，which can be divided into five sand-body architecture models：deep cut and superimposition in a large area，shallow cut and superimposition in a small area，no cut and crossing superimposition，no cut and layering superimposition，and isolating sand-body architecture model. Five architectural elements for braided river reservoirs were identified，i.e. channel filling，downstream accretion，sandy bed form，sand sheet and overbank fines. Mid-channel bar，filled by downstream accretion sand，is the most important architectural element within sand-body，in which the architecture model shows downstream accretion characteristic.
To establish different levels of reservoir architectures of the braided river sedimentary system for adjustment and remaining oil exploration，based on the hierarchical level system of fluvial facies，the architecture interfaces of braided river reservoir in Ying-13 fault block can be classified into six hierarchies，and the causes and distribution characteristics of 3-6 hierarchy architecture interfaces were determined. According to different levels of architecture interfaces，based on sequence stratigraphy，analysis of spatial stacking pattern of channel sand-body，classification of architectural element，internal anatomy of mid-channel bar，etc.，the architecture model of the braided river have been categorized into four different levels，from large to small in turn which are complex braided river sand-body，fluvial sand-body，internal sand-body and internal mid-beach bar. Four-different stages channel complex sand-bodies developed in Dong2 oil bed of Ying-13 fault block，which can be divided into five sand-body architecture models：deep cut and superimposition in a large area，shallow cut and superimposition in a small area，no cut and crossing superimposition，no cut and layering superimposition，and isolating sand-body architecture model. Five architectural elements for braided river reservoirs were identified，i.e. channel filling，downstream accretion，sandy bed form，sand sheet and overbank fines. Mid-channel bar，filled by downstream accretion sand，is the most important architectural element within sand-body，in which the architecture model shows downstream accretion characteristic.
2015, 22(4):38-43.
Abstract:
Dinan uplift of Junggar Basin is an important hydrocarbon accumulation zone in Ludong area with better hydrocarbon source and good reservoir-cap configuration，where industrial oil flow has been discovered in several strata from Carboniferous to Cretaceous. But the Cretaceous was lack of systematic research. Cretaceous Qingshuihe Formation has been correlated and divided in detail based on seismic data and logging data from 60 wells guided by sequence stratigraphic theory，and then its sequency stratigraphic characteristics，sedimentary characteristics and evolution were analyzed. The research results show that the Qingshuihe Formation can be divided into K1q1，K1q2，K1q3，K1q4 and K1q5 from bottom to top，and basal conglomerate strata in the K1q1-K1q4 distributed diachronously. The Qingshuihe Formation was identified as a third order sequence which consists of LST，TST and HST from bottom to top and forming a complete set of lake level change cycle. Braided river delta facies and lacustrine facies were identified and provenance changed from north-west to south in a plane. Good reservoir conditions in the braided river delta and diachronous distribution of basal conglomerate provide favorable conditions for hydrocarbon accumulating in stratigraphic and lithologic reservoirs. The basal conglomerate distributed along four overlap pinching out belts in the K1q1 to K1q4 could be regarded as next exploration targets.
Dinan uplift of Junggar Basin is an important hydrocarbon accumulation zone in Ludong area with better hydrocarbon source and good reservoir-cap configuration，where industrial oil flow has been discovered in several strata from Carboniferous to Cretaceous. But the Cretaceous was lack of systematic research. Cretaceous Qingshuihe Formation has been correlated and divided in detail based on seismic data and logging data from 60 wells guided by sequence stratigraphic theory，and then its sequency stratigraphic characteristics，sedimentary characteristics and evolution were analyzed. The research results show that the Qingshuihe Formation can be divided into K1q1，K1q2，K1q3，K1q4 and K1q5 from bottom to top，and basal conglomerate strata in the K1q1-K1q4 distributed diachronously. The Qingshuihe Formation was identified as a third order sequence which consists of LST，TST and HST from bottom to top and forming a complete set of lake level change cycle. Braided river delta facies and lacustrine facies were identified and provenance changed from north-west to south in a plane. Good reservoir conditions in the braided river delta and diachronous distribution of basal conglomerate provide favorable conditions for hydrocarbon accumulating in stratigraphic and lithologic reservoirs. The basal conglomerate distributed along four overlap pinching out belts in the K1q1 to K1q4 could be regarded as next exploration targets.
2015, 22(4):44-48.
Abstract:
Karst collapsed columns are widely developed in Qinshui basin，which has great influence on formation and distribution of gas accumulation. In order to analyze its influence on gas accumulation，by studying the column’s formation conditions，characteristics and distribution，it is found that the columns mainly formed during the time of Himalayan movement；they distribute in groups in the plane and most of them are half columns with a general diameter range of 100-300 m，cut through the upper main coal bed，namely the 3rd coal bed. Lots of broken belts and decompaction belts developed in the collapsed columns，which provide pathways for the gas accumulating in coal and sandstone to migrate outside. The seam pressure declines after the formed columns cut through the coal bed，which provides conditions for the coal seam gas desorption. The collapsed columns also communicate the seam vertically with the upper and the lower adjacent aquifers，which results in the hydrodynamic connectivity of different strata and the migration of desorbed gas into the upper stratum in free state or accompanying with underwater circulation. So the collapsed columns would play a role in destroying the gas accumulation in the coal measure strata，which leads to a low coal seam gas concentration around the columns and a decline methane concentration and an increasing concentration of N2，CO2. Additionally，several collapsed columns play a role in migrating seam gas into shallow strata to form new gas reservoirs. But most of the cases show that the areas influenced by the columns are always limited.
Karst collapsed columns are widely developed in Qinshui basin，which has great influence on formation and distribution of gas accumulation. In order to analyze its influence on gas accumulation，by studying the column’s formation conditions，characteristics and distribution，it is found that the columns mainly formed during the time of Himalayan movement；they distribute in groups in the plane and most of them are half columns with a general diameter range of 100-300 m，cut through the upper main coal bed，namely the 3rd coal bed. Lots of broken belts and decompaction belts developed in the collapsed columns，which provide pathways for the gas accumulating in coal and sandstone to migrate outside. The seam pressure declines after the formed columns cut through the coal bed，which provides conditions for the coal seam gas desorption. The collapsed columns also communicate the seam vertically with the upper and the lower adjacent aquifers，which results in the hydrodynamic connectivity of different strata and the migration of desorbed gas into the upper stratum in free state or accompanying with underwater circulation. So the collapsed columns would play a role in destroying the gas accumulation in the coal measure strata，which leads to a low coal seam gas concentration around the columns and a decline methane concentration and an increasing concentration of N2，CO2. Additionally，several collapsed columns play a role in migrating seam gas into shallow strata to form new gas reservoirs. But most of the cases show that the areas influenced by the columns are always limited.
2015, 22(4):49-53.
Abstract:
Porosity is an important parameter of reservoir rock，which is mainly used to evaluate reservoir physical properties and to calculate original reserves of petroleum. Pore structure characterization of tight oil reservoir is mainly on micronano scale. The tight oil reservoir porosity is generally less than10%. It is difficult to measure tight oil reservoir porosity accurately and quickly using conventional methods. Based on Boyle’s law and pressure differentiation function of porosity measuring，parameters affecting the accuracy of porosity measurement were analyzed. Also，experimental instrument parameters were optimized. Experimental apparatus for porosity determination，which is suitable for the tight oil reservoir，was designed. The porosity of a core sample is 2.55% using the experimental apparatus，while the core porosity is 2.40% using mercury intrusion method. The two results agrees. In order to verify the accuracy of the experimental apparatus，the porosity of an artificial core which is 25.16% was measured using the optimized experimental apparatus. The result is 25.56%.Therefore，porosity of the tight samples can be quickly and accurately determined by the optimized experimental apparatus.
Porosity is an important parameter of reservoir rock，which is mainly used to evaluate reservoir physical properties and to calculate original reserves of petroleum. Pore structure characterization of tight oil reservoir is mainly on micronano scale. The tight oil reservoir porosity is generally less than10%. It is difficult to measure tight oil reservoir porosity accurately and quickly using conventional methods. Based on Boyle’s law and pressure differentiation function of porosity measuring，parameters affecting the accuracy of porosity measurement were analyzed. Also，experimental instrument parameters were optimized. Experimental apparatus for porosity determination，which is suitable for the tight oil reservoir，was designed. The porosity of a core sample is 2.55% using the experimental apparatus，while the core porosity is 2.40% using mercury intrusion method. The two results agrees. In order to verify the accuracy of the experimental apparatus，the porosity of an artificial core which is 25.16% was measured using the optimized experimental apparatus. The result is 25.56%.Therefore，porosity of the tight samples can be quickly and accurately determined by the optimized experimental apparatus.
2015, 22(4):54-58.
Abstract:
Cathodoluminescence analysis of the carbonate mineral composition and structure is one of the most effective technical methods to research visually and quickly on carbonate reservoir diagenesis environment and its genesis. In this paper，cathodoluminescence features of calcite，filling in Ordovician carbonate fractured-vuggy reservoir，was analyzed further to instruct its diagenetic environment combined with the analysis of Fe-Mn-Sr trace elements and the homogenization temperature of fluid inclusion. Studies have shown that the content of Mn2+ and Fe2+ and cathodoluminescence characteristics largely reflects the diagenetic environment under oxidation-reduction conditions. Bright glow（high Mn2+）suggests the diagenetic environment was under reducing conditions，or it may be related to the stagnant oxide water connected with nonluminance cementation. Dark or non-luminescence suggests the diagenetic environment was under the conditions of oxidation when Mn2+ tended to be oxidized to higher state and difficult to replace Ca2+ and get into the lattice. The luminance of calcite filling in different typical fractured-vuggy reservoir，combined with the content and ratio of Mn2+ and Fe2+，could be used to indicate different diagenetic environment and filling period which show the complexity and multiple phases of the fractured-vuggy forming and filling in the study area.
Cathodoluminescence analysis of the carbonate mineral composition and structure is one of the most effective technical methods to research visually and quickly on carbonate reservoir diagenesis environment and its genesis. In this paper，cathodoluminescence features of calcite，filling in Ordovician carbonate fractured-vuggy reservoir，was analyzed further to instruct its diagenetic environment combined with the analysis of Fe-Mn-Sr trace elements and the homogenization temperature of fluid inclusion. Studies have shown that the content of Mn2+ and Fe2+ and cathodoluminescence characteristics largely reflects the diagenetic environment under oxidation-reduction conditions. Bright glow（high Mn2+）suggests the diagenetic environment was under reducing conditions，or it may be related to the stagnant oxide water connected with nonluminance cementation. Dark or non-luminescence suggests the diagenetic environment was under the conditions of oxidation when Mn2+ tended to be oxidized to higher state and difficult to replace Ca2+ and get into the lattice. The luminance of calcite filling in different typical fractured-vuggy reservoir，combined with the content and ratio of Mn2+ and Fe2+，could be used to indicate different diagenetic environment and filling period which show the complexity and multiple phases of the fractured-vuggy forming and filling in the study area.
2015, 22(4):59-63.
Abstract:
A detailed study about the mineral composition of the upper Ordovician Wufeng shale and the lower Silurian Longmaxi shale in southern Sichuan Basin was conducted by the measurements on core and outcrop samples including XRD （X-ray diffraction），thin slices observation，SEM（Scanning Electron Microscope）and QEMSCAN（Quantitatively Electron Microscope Scanning）. The results obtained show that quartz and clay minerals are the dominant minerals in this shale，followed by calcite and dolomite，with a small amount of potassium feldspar，plagioclase and pyrite. The quartz is mainly from terrigenous clastic sources while some of them is biogenous. The clay minerals are characterized by a combination of illite and chlorite；and the calcite and dolomite mainly act as cement and fracture filling in the shale. Based on mineral composition，the Wufeng-Longmaxi shale is classified into three lithofacies：quartz-rich shale，clay-rich shale and carbonate-rich shale，which have significant differences in the mineral composition，texture，fabric and depositional background. The calculated brittle index of 0.36-0.74（0.51 on average）for the Wufeng-Longmaxi shale indicates that this shale is favorable for hydraulic fracture to produce shale gas. The shale at the bottom has higher quartz content，larger brittleness index and richer in organic matter，which is favorable for shale gas enrichment and reservoir fracturing.
A detailed study about the mineral composition of the upper Ordovician Wufeng shale and the lower Silurian Longmaxi shale in southern Sichuan Basin was conducted by the measurements on core and outcrop samples including XRD （X-ray diffraction），thin slices observation，SEM（Scanning Electron Microscope）and QEMSCAN（Quantitatively Electron Microscope Scanning）. The results obtained show that quartz and clay minerals are the dominant minerals in this shale，followed by calcite and dolomite，with a small amount of potassium feldspar，plagioclase and pyrite. The quartz is mainly from terrigenous clastic sources while some of them is biogenous. The clay minerals are characterized by a combination of illite and chlorite；and the calcite and dolomite mainly act as cement and fracture filling in the shale. Based on mineral composition，the Wufeng-Longmaxi shale is classified into three lithofacies：quartz-rich shale，clay-rich shale and carbonate-rich shale，which have significant differences in the mineral composition，texture，fabric and depositional background. The calculated brittle index of 0.36-0.74（0.51 on average）for the Wufeng-Longmaxi shale indicates that this shale is favorable for hydraulic fracture to produce shale gas. The shale at the bottom has higher quartz content，larger brittleness index and richer in organic matter，which is favorable for shale gas enrichment and reservoir fracturing.
2015, 22(4):64-68.
Abstract:
The characteristics of reservoir and its control factors of Es3 member in Area 4，Bonan oilfield were studied using data of core observation and description，casting thin sections，scanning electron microscope and core laboratory analysis.The analysis results show that the reservoir of Es3 member is characterized by low compositional maturity and textural maturity of sandstone，poor physical property and development of secondary dissolution pore，which is controlled by deposition macroscopically and by diagenetic reform microcosmically. The main reason leading to the poor reservoir physical property is compaction，followed by cementation. Dissolution develops well to improve reservoir performance. On the basis of diagenesis study and diagenetic facies analysis，the reservoir diagenetic facies in the study area were divided into 4 types：residual intergranular pore after compaction-unstable component dissolution facies，secondary kaolinite intergranular pore-quartz overgrowth facies，filling and half-filling microfracture-carbonate cementation facies，severe compaction-matrix filling facies. The drilling data in the area reveal that high-quality reservoirs mainly distribute in residual intergranular pore-unsta? ble component dissolution diagenetic facies.
The characteristics of reservoir and its control factors of Es3 member in Area 4，Bonan oilfield were studied using data of core observation and description，casting thin sections，scanning electron microscope and core laboratory analysis.The analysis results show that the reservoir of Es3 member is characterized by low compositional maturity and textural maturity of sandstone，poor physical property and development of secondary dissolution pore，which is controlled by deposition macroscopically and by diagenetic reform microcosmically. The main reason leading to the poor reservoir physical property is compaction，followed by cementation. Dissolution develops well to improve reservoir performance. On the basis of diagenesis study and diagenetic facies analysis，the reservoir diagenetic facies in the study area were divided into 4 types：residual intergranular pore after compaction-unstable component dissolution facies，secondary kaolinite intergranular pore-quartz overgrowth facies，filling and half-filling microfracture-carbonate cementation facies，severe compaction-matrix filling facies. The drilling data in the area reveal that high-quality reservoirs mainly distribute in residual intergranular pore-unsta? ble component dissolution diagenetic facies.
2015, 22(4):69-73.
Abstract:
The metamorphic buried hill reservoir that bearing hydrocarbons develops in JZ25-1 oilfield，in which the main reservoir space is fracture in the study area. The porosity is an important standard for fracture reservoir evaluation，so the key factors of reservoir exploration and development are effective predictions on fracture development zone and porosity.Metamorphic rock reservoir in JZ25-1 oilfield was predicted using pre-stack elastic wave impedance inversion by integrating previous research results and making a comprehensive analysis of well logging and seismic data. The recognition criteria of fracture reservoir in the study area were determined through establishing the relationship between S-wave impedance and fracture reservoir porosity，and then the characteristics of fracture reservoir distribution were analyzed. Research results show that weathering crust，fracture zone，tight zone and two sets of reservoirs develop in the buried hill formation in the study area. The upper reservoir develops on the top of the weathering crust，and the lower reservoir develops in the fracture zone which is the main fracture reservoirs in the study area. The fracture reservoir spreads along the NE faults，and mainly distributes at structural highs of the buried-hill horizontally，while in the profile，it is characterized by poor reflection continuity and nearly layered formation. The better fractured reservoir develops mainly in the middle and the south of the study area. Regional structural highs in the southern part with porosity larger than 6.5% and parts near the fracture development zone should be favorable areas for the next oil and gas exploration.
The metamorphic buried hill reservoir that bearing hydrocarbons develops in JZ25-1 oilfield，in which the main reservoir space is fracture in the study area. The porosity is an important standard for fracture reservoir evaluation，so the key factors of reservoir exploration and development are effective predictions on fracture development zone and porosity.Metamorphic rock reservoir in JZ25-1 oilfield was predicted using pre-stack elastic wave impedance inversion by integrating previous research results and making a comprehensive analysis of well logging and seismic data. The recognition criteria of fracture reservoir in the study area were determined through establishing the relationship between S-wave impedance and fracture reservoir porosity，and then the characteristics of fracture reservoir distribution were analyzed. Research results show that weathering crust，fracture zone，tight zone and two sets of reservoirs develop in the buried hill formation in the study area. The upper reservoir develops on the top of the weathering crust，and the lower reservoir develops in the fracture zone which is the main fracture reservoirs in the study area. The fracture reservoir spreads along the NE faults，and mainly distributes at structural highs of the buried-hill horizontally，while in the profile，it is characterized by poor reflection continuity and nearly layered formation. The better fractured reservoir develops mainly in the middle and the south of the study area. Regional structural highs in the southern part with porosity larger than 6.5% and parts near the fracture development zone should be favorable areas for the next oil and gas exploration.
2015, 22(4):74-78.
Abstract:
It is difficult to use the original seismic data directly to describe the thin reservoir of subtle hydrocarbon reservoir due to seismic resolution and wave form interference. The reflection coefficient inversion based on reflection coefficient data cube is an inversion technology：original seismic data are firstly processed by amplitude preserving and data denoising and time varying wavelet and space varying wavelet are extracted respectively to construct wavelet inverse transform factor，then frequency cube obtained by frequency division algorithm is selected to construct the geological conditions，and finally reflection coefficient data cube for data interpretation are calculated and obtained. In this way，all kinds of interference phenomena can be eliminated effectively and the resolution of seismic data can be improved. According to the problems of the thin sand body in the Cretaceous reservoir of Chepaizi area and the poor corresponding relationship between the reservoir and seismic reflection，the thin reservoir of subtle hydrocarbon reservoir in the study area was described based on reflection coefficient inversion. Results show that the sand bodies stretch along nearly south-north discontinuously in belt or in massive block，mainly distribute in the eastern and western coastal areas of the study area，which agrees with the sedimentary law that the Cretaceous mainly develops shore-shallow lacustrine sand body as well as regional fan delta sand body. According to the inversion results，the pinchout line of reservoir was extrapolated reasonably to the shore to expand the effective range of the lithologic trap distribution.
It is difficult to use the original seismic data directly to describe the thin reservoir of subtle hydrocarbon reservoir due to seismic resolution and wave form interference. The reflection coefficient inversion based on reflection coefficient data cube is an inversion technology：original seismic data are firstly processed by amplitude preserving and data denoising and time varying wavelet and space varying wavelet are extracted respectively to construct wavelet inverse transform factor，then frequency cube obtained by frequency division algorithm is selected to construct the geological conditions，and finally reflection coefficient data cube for data interpretation are calculated and obtained. In this way，all kinds of interference phenomena can be eliminated effectively and the resolution of seismic data can be improved. According to the problems of the thin sand body in the Cretaceous reservoir of Chepaizi area and the poor corresponding relationship between the reservoir and seismic reflection，the thin reservoir of subtle hydrocarbon reservoir in the study area was described based on reflection coefficient inversion. Results show that the sand bodies stretch along nearly south-north discontinuously in belt or in massive block，mainly distribute in the eastern and western coastal areas of the study area，which agrees with the sedimentary law that the Cretaceous mainly develops shore-shallow lacustrine sand body as well as regional fan delta sand body. According to the inversion results，the pinchout line of reservoir was extrapolated reasonably to the shore to expand the effective range of the lithologic trap distribution.
2015, 22(4):79-86.
Abstract:
Old oilfields in China have successively entered into middle to late stage of oil production. Affected by strong reservoir heterogeneity，large amounts of remaining oils are still in the subsurface and provide an important material foundation for a long-term stable yield in old oilfields. It is a highly integrated and difficult research problem to predict potential areas of remaining oil under high water cut condition. The theoretical and practical prediction have never ceased but with fewer researches on enrichment mechanism of remaining oils. Research on oil-water flow rule is the key of water flooding in the low-permeability reservoirs. Oil-water rate difference and capillary force is not considered in Buckley-Leverett principle. Based on the theory of fluid potential energy and petroleum migration and accumulation，the formulae of oil-water seepage velocity and reservoir forming velocity of remaining oil re-enrichment in the whole fluid migration course of water flooding were deduced first in consideration of two states，oil in water and water in oil，in water-wet reservoir by means of force analysis using Darcy’s Law. The reservoir forming mechanism of remaining oil re-enrichment at different develop? ment stages in the water flooding reservoir was proposed. The research results show that the hydrodynamic force has a big impact on the remaining oil re-enrichment velocity in water flooding reservoir，and the remaining oil re-enrichment velocity increases with the increase of air permeability，water saturation and oil-water density difference，and it decreases with the increase of hydrodynamic pressure gradient，crude oil viscosity and dip angle. The field application indicates that the mechanism of remaining oil re-enrichment in the water flooding reservoir is reasonable and practical.
Old oilfields in China have successively entered into middle to late stage of oil production. Affected by strong reservoir heterogeneity，large amounts of remaining oils are still in the subsurface and provide an important material foundation for a long-term stable yield in old oilfields. It is a highly integrated and difficult research problem to predict potential areas of remaining oil under high water cut condition. The theoretical and practical prediction have never ceased but with fewer researches on enrichment mechanism of remaining oils. Research on oil-water flow rule is the key of water flooding in the low-permeability reservoirs. Oil-water rate difference and capillary force is not considered in Buckley-Leverett principle. Based on the theory of fluid potential energy and petroleum migration and accumulation，the formulae of oil-water seepage velocity and reservoir forming velocity of remaining oil re-enrichment in the whole fluid migration course of water flooding were deduced first in consideration of two states，oil in water and water in oil，in water-wet reservoir by means of force analysis using Darcy’s Law. The reservoir forming mechanism of remaining oil re-enrichment at different develop? ment stages in the water flooding reservoir was proposed. The research results show that the hydrodynamic force has a big impact on the remaining oil re-enrichment velocity in water flooding reservoir，and the remaining oil re-enrichment velocity increases with the increase of air permeability，water saturation and oil-water density difference，and it decreases with the increase of hydrodynamic pressure gradient，crude oil viscosity and dip angle. The field application indicates that the mechanism of remaining oil re-enrichment in the water flooding reservoir is reasonable and practical.
2015, 22(4):87-92.
Abstract:
Branched-preformed particle gel（B-PPG）is a novel oil displacement agent，which has a crosslinked network and linear branched chains. When mixed with water or brine，B-PPG is not dissolved completely and the produced mixture is a heterogeneous suspension system. The rheological properties of B-PPG with different concentrations and different crosslinked degrees in brine were studied by steady shear and dynamic oscillation test；and the mechanism was also discussed from the viewpoint of molecular structure. The results show that B-PPG suspension has excellent viscoelasticity，salt tolerance and rheological properties. With the increase of crosslinked degree，the viscosity of B-PPG suspension decreases，as well as the frequency at crossing point of viscosity and elasticity（Fc）. High salinity makes the elasticity of HPAM solution decrease and has few effects on B-PPG，which proves that B-PPG has better salt tolerance. The viscosity and linear viscoelastic region of B-PPG suspension increase and Fc decreases with increasing concentration. Moreover，BPPG suspension shows weak gel character by linear fitting of dynamic oscillation curve.
Branched-preformed particle gel（B-PPG）is a novel oil displacement agent，which has a crosslinked network and linear branched chains. When mixed with water or brine，B-PPG is not dissolved completely and the produced mixture is a heterogeneous suspension system. The rheological properties of B-PPG with different concentrations and different crosslinked degrees in brine were studied by steady shear and dynamic oscillation test；and the mechanism was also discussed from the viewpoint of molecular structure. The results show that B-PPG suspension has excellent viscoelasticity，salt tolerance and rheological properties. With the increase of crosslinked degree，the viscosity of B-PPG suspension decreases，as well as the frequency at crossing point of viscosity and elasticity（Fc）. High salinity makes the elasticity of HPAM solution decrease and has few effects on B-PPG，which proves that B-PPG has better salt tolerance. The viscosity and linear viscoelastic region of B-PPG suspension increase and Fc decreases with increasing concentration. Moreover，BPPG suspension shows weak gel character by linear fitting of dynamic oscillation curve.
2015, 22(4):93-96.
Abstract:
With the exploitation of heavy oil reservoir，hydrogen sulfide released in the process of heavy oil thermal recovery continually increases. Especially in steam drive block，the discharge of hydrogen sulfide surges，detrimentally affecting the safety production of the heavy oil thermal recovery block. In order to further understand the mechanism of the generation of hydrogen sulfide in the process of heavy oil thermal recovery，factors such as the water content，the processing temperature and the processing time were tested. The results show that the transformation of different forms of sulfides to hydrogen sulfide can be maximized under the conditions of 20% of water content，260 ℃ of processing temperature and 48 h of processing time for the target heavy oil. In the process of heavy oil thermal recovery，mercaptan sulfur and thioether sulfur contribute to the generation of hydrogen sulfide，while thiophenic sulfur has no contribution. Analysis on contribution of different forms of sulfides to sulfide hydrogen produced in the thermal recovery of heavy oil can provide technical supports for the corresponding prevention measures in the exploitation of high sulfur block.
With the exploitation of heavy oil reservoir，hydrogen sulfide released in the process of heavy oil thermal recovery continually increases. Especially in steam drive block，the discharge of hydrogen sulfide surges，detrimentally affecting the safety production of the heavy oil thermal recovery block. In order to further understand the mechanism of the generation of hydrogen sulfide in the process of heavy oil thermal recovery，factors such as the water content，the processing temperature and the processing time were tested. The results show that the transformation of different forms of sulfides to hydrogen sulfide can be maximized under the conditions of 20% of water content，260 ℃ of processing temperature and 48 h of processing time for the target heavy oil. In the process of heavy oil thermal recovery，mercaptan sulfur and thioether sulfur contribute to the generation of hydrogen sulfide，while thiophenic sulfur has no contribution. Analysis on contribution of different forms of sulfides to sulfide hydrogen produced in the thermal recovery of heavy oil can provide technical supports for the corresponding prevention measures in the exploitation of high sulfur block.
2015, 22(4):97-102.
Abstract:
Pore-throat structure before and after strong base ASP flooding in Daqing oilfield was researched qualitatively and quantitatively using mercury injection，rate-controlled mercury injection，SEM and casting thin sections analysis. The results show that grain boundaries are dissolved and zigzag-like with unclear edges and corners，and feldspar is dissolved seriously by alkali after base ASP flooding. A large number of dissolution pores were observed. Kaolinite is dissolved and secondary quartz formed on clay mineral surface at the same time. White cloud-like scale deposits filling in pores result in changes in pore structure and partial pores are plugged. Average core throat radius dropped by 6.528% and average pore radius dropped by 3.360%. Pore-throat ratio had wider distribution and increased by 12.839% averagely. The final oil saturation was lower than that of water drive core and its final oil saturation coefficient was smaller. The residual oil saturation and ultimate oil saturation decreased with the increase of core permeability before and after strong base damage. Permeability ratio changed from 5.567 to 5.691 after the strong base ASP flooding. The stronger core heterogeneity brings more possi? bility of fingering and channeling. The poor pore throat structure will greatly influence the subsequent water flooding and the implementation of enhancing oil recovery method，and also bring about difficulties in thin and poor layers.
Pore-throat structure before and after strong base ASP flooding in Daqing oilfield was researched qualitatively and quantitatively using mercury injection，rate-controlled mercury injection，SEM and casting thin sections analysis. The results show that grain boundaries are dissolved and zigzag-like with unclear edges and corners，and feldspar is dissolved seriously by alkali after base ASP flooding. A large number of dissolution pores were observed. Kaolinite is dissolved and secondary quartz formed on clay mineral surface at the same time. White cloud-like scale deposits filling in pores result in changes in pore structure and partial pores are plugged. Average core throat radius dropped by 6.528% and average pore radius dropped by 3.360%. Pore-throat ratio had wider distribution and increased by 12.839% averagely. The final oil saturation was lower than that of water drive core and its final oil saturation coefficient was smaller. The residual oil saturation and ultimate oil saturation decreased with the increase of core permeability before and after strong base damage. Permeability ratio changed from 5.567 to 5.691 after the strong base ASP flooding. The stronger core heterogeneity brings more possi? bility of fingering and channeling. The poor pore throat structure will greatly influence the subsequent water flooding and the implementation of enhancing oil recovery method，and also bring about difficulties in thin and poor layers.
2015, 22(4):103-108.
Abstract:
Equilibrium displacement is the basic principle for well pattern design in waterflood oilfield. For the case of buried hill reservoir with dominant mid-high angle fractures and large vertical thickness，the gravity of fluid has significant influence on equilibrium displacement in stereo well pattern. Based on percolation theory，taking five-spot stereo horizontal well pattern for instance，formulas for water breakthrough time of production well considering the gravity and that for injection-production well spacing while equilibrium displacement were established. The place of central horizontal well was calculated according to the selected oil reservoir parameters and was optimized using numerical simulation method. The results indicate that the error between calculation and numerical simulation is 4.73% which is allowable in experiment，and the reliability of the formula is verified. The water breakthrough time difference between vertical production wells decreases and then increases as the central injection well rises layer by layer. When the injection well of S2 locates in the 6th layer，equilibrium displacement is realized that the breakthrough time difference between S1 and S3 is the lowest. The degree of reserve recovery reaches 42.52%，which is the peak value，and is improved by 3.84% compared with that when S2 locates in 11th layer.When the equilibrium displacement is realized，the ratio of injection-production distance from S2 to S1 and that from S2 to S3 is 2.95. Therefore，well spacing adjustment could improve development by impairing non-equilibrium displacement induced by gravitational effect.
Equilibrium displacement is the basic principle for well pattern design in waterflood oilfield. For the case of buried hill reservoir with dominant mid-high angle fractures and large vertical thickness，the gravity of fluid has significant influence on equilibrium displacement in stereo well pattern. Based on percolation theory，taking five-spot stereo horizontal well pattern for instance，formulas for water breakthrough time of production well considering the gravity and that for injection-production well spacing while equilibrium displacement were established. The place of central horizontal well was calculated according to the selected oil reservoir parameters and was optimized using numerical simulation method. The results indicate that the error between calculation and numerical simulation is 4.73% which is allowable in experiment，and the reliability of the formula is verified. The water breakthrough time difference between vertical production wells decreases and then increases as the central injection well rises layer by layer. When the injection well of S2 locates in the 6th layer，equilibrium displacement is realized that the breakthrough time difference between S1 and S3 is the lowest. The degree of reserve recovery reaches 42.52%，which is the peak value，and is improved by 3.84% compared with that when S2 locates in 11th layer.When the equilibrium displacement is realized，the ratio of injection-production distance from S2 to S1 and that from S2 to S3 is 2.95. Therefore，well spacing adjustment could improve development by impairing non-equilibrium displacement induced by gravitational effect.
2015, 22(4):109-113.
Abstract:
Viscosity reduction experiments of new Gemini surfactant RB107 was done to solve the problems of high content of colloid and asphaltenes in formations，high viscosity of heavy oil and low recovery efficiency of water flooding in offshore S oilfield. Emulsion concentration，aggregation morphology，interfacial activity，wettability，stability and other properties of the surfactant were evaluated and its oil displacement performance was investigated through physical simulation experiment. When mass fraction is 0.3% and oil-water volume ratio is 50∶50，the viscosity of the heavy oil may be decreased by 97% and oil-water interfacial tension may be dropped to 0.165 6 mN/m under the condition of oil reservoir. The results show that RB107 has strong performance of viscosity reduction and interfacial activity under low concentration. RB107 also has fast emulsification speed（0.24 mL/min）and strong stability with uniformly dispersed oil-water emulsion droplets of small diameter. Contact angle of RB107 solution was 10.8° on oil base，which shows that RB107 has a strong wettability on the oil-water interface. Compared with water flooding results，physical simulation results of RB107 could enhance the oil recovery by 10.1%. RB107 could be the viscosity breaker of the heavy oil in S oilfield for its good viscosity reduction effect.
Viscosity reduction experiments of new Gemini surfactant RB107 was done to solve the problems of high content of colloid and asphaltenes in formations，high viscosity of heavy oil and low recovery efficiency of water flooding in offshore S oilfield. Emulsion concentration，aggregation morphology，interfacial activity，wettability，stability and other properties of the surfactant were evaluated and its oil displacement performance was investigated through physical simulation experiment. When mass fraction is 0.3% and oil-water volume ratio is 50∶50，the viscosity of the heavy oil may be decreased by 97% and oil-water interfacial tension may be dropped to 0.165 6 mN/m under the condition of oil reservoir. The results show that RB107 has strong performance of viscosity reduction and interfacial activity under low concentration. RB107 also has fast emulsification speed（0.24 mL/min）and strong stability with uniformly dispersed oil-water emulsion droplets of small diameter. Contact angle of RB107 solution was 10.8° on oil base，which shows that RB107 has a strong wettability on the oil-water interface. Compared with water flooding results，physical simulation results of RB107 could enhance the oil recovery by 10.1%. RB107 could be the viscosity breaker of the heavy oil in S oilfield for its good viscosity reduction effect.
2015, 22(4):114-117.
Abstract:
There are some difficulties in the development of Hai26 block in Liaohe oilfield，such as high oil viscosity and poor performance of conventional water flooding. Based on the evaluation of surface activity，interfacial tension，temperature tolerance and absorbability of ten kinds of surfactants，the most suitable surfactant was selected for Hai26 block.Through the one dimension flooding experiment，the injected water temperature，the influence of surfactant concentration and injection way on the recovery ratio was explored. The results showed that：as the injected water temperature increased， the recovery ratio increased at the same time，and the recovery ratio changed smoothly when the temperature was above 120 ℃. The recovery ratio increased with the concentration of the surfactant until it reached to 0.3%. The recovery ratio of multi-slug injected way was higher than that of single slug injected way. At the optimized conditions，the injected water temperature of 120 ℃，the surfactant concentration of 0.3% and 4 cycles of alternating injection，the ultimate recovery efficiency of hot water and surfactant flooding was 83.67%.
There are some difficulties in the development of Hai26 block in Liaohe oilfield，such as high oil viscosity and poor performance of conventional water flooding. Based on the evaluation of surface activity，interfacial tension，temperature tolerance and absorbability of ten kinds of surfactants，the most suitable surfactant was selected for Hai26 block.Through the one dimension flooding experiment，the injected water temperature，the influence of surfactant concentration and injection way on the recovery ratio was explored. The results showed that：as the injected water temperature increased， the recovery ratio increased at the same time，and the recovery ratio changed smoothly when the temperature was above 120 ℃. The recovery ratio increased with the concentration of the surfactant until it reached to 0.3%. The recovery ratio of multi-slug injected way was higher than that of single slug injected way. At the optimized conditions，the injected water temperature of 120 ℃，the surfactant concentration of 0.3% and 4 cycles of alternating injection，the ultimate recovery efficiency of hot water and surfactant flooding was 83.67%.
2015, 22(4):118-122.
Abstract:
In the processes of steam flooding in heavy oil reservoirs，the steam overlay and channeling often occur，which leads to small sweep efficiency of steam and low recovery efficiency of oil. Aiming at these problems，three experiments were conducted with a three-dimension displacement system，which included steam flooding，steam flooding converting to urea assisted steam flooding and steam flooding converting to urea-foam assisted steam flooding. The results show that the effect of the conventional steam flooding is not satisfactory；however，that of steam flooding converting to urea assisted or to urea-foam assisted steam flooding is better. After the conversion points of these two experiments，the instantaneous oil steam ratio was increased by 0.24 and 0.27 respectively；the recovery efficiency was improved by 9.56% and 16.29% respectively；the pressure difference between inlet and outlet increased by 0.18 and 0.33 MPa respectively and the instantaneous water cut decreased by 15.77% and 36.80% respectively. Variation of three-dimension temperature fields shows that the urea assisted steam flooding can expand the steam swept area but the effect is not obvious，and the urea-foam assisted steam flooding can control the steam overlay and channeling effectively and improve the sweep efficiency of the steam and produced degree of the oil. Comprehensive comparison of the above indexes indicates that the effect of urea-foam assisted steam flooding is the best.
In the processes of steam flooding in heavy oil reservoirs，the steam overlay and channeling often occur，which leads to small sweep efficiency of steam and low recovery efficiency of oil. Aiming at these problems，three experiments were conducted with a three-dimension displacement system，which included steam flooding，steam flooding converting to urea assisted steam flooding and steam flooding converting to urea-foam assisted steam flooding. The results show that the effect of the conventional steam flooding is not satisfactory；however，that of steam flooding converting to urea assisted or to urea-foam assisted steam flooding is better. After the conversion points of these two experiments，the instantaneous oil steam ratio was increased by 0.24 and 0.27 respectively；the recovery efficiency was improved by 9.56% and 16.29% respectively；the pressure difference between inlet and outlet increased by 0.18 and 0.33 MPa respectively and the instantaneous water cut decreased by 15.77% and 36.80% respectively. Variation of three-dimension temperature fields shows that the urea assisted steam flooding can expand the steam swept area but the effect is not obvious，and the urea-foam assisted steam flooding can control the steam overlay and channeling effectively and improve the sweep efficiency of the steam and produced degree of the oil. Comprehensive comparison of the above indexes indicates that the effect of urea-foam assisted steam flooding is the best.
2015, 22(4):123-126.
Abstract:
Hydraulic fracturing is an important technical method for improving the reservoir production，whose aim is forming fractures with high conductivity. The shape of sand banks developed by the settlement of proppant particles determines the stimulation performance. Large scale visible fracture simulator was used to carry out the proppant settlement stimulation experiment based on abundant theoretical researches and scarce experimental studies in China. The sand carrying capability of four kinds of commonly used fracturing fluids，including slick water，linear gel，fiber liquid and crosslinked flu? id，have been evaluated after the shape of sand banks，and the proppant settlement velocity and horizontal migration velocity were analyzed. The results show that the slick water can develop short and high sand banks，so it has the worst sand carrying capability. Crosslinked fluid can develop long and low sand banks，which is also the most gradual one，so it has the best sand carrying capability. The sand carrying capabilities of the linear gel and fiber liquid are between them. The horizontal migration velocities of proppant particles in four kinds of fracturing fluids are 78 percent，85 percent，91 percent and 95 percent of fluid velocity，and the settlement velocities from high to low are slick water，linear gel，fiber liquid and crosslinked fluid respectively. So the appropriate fracturing fluids should be chosen based on the reservoir parameters and the types of fractures in the field.
Hydraulic fracturing is an important technical method for improving the reservoir production，whose aim is forming fractures with high conductivity. The shape of sand banks developed by the settlement of proppant particles determines the stimulation performance. Large scale visible fracture simulator was used to carry out the proppant settlement stimulation experiment based on abundant theoretical researches and scarce experimental studies in China. The sand carrying capability of four kinds of commonly used fracturing fluids，including slick water，linear gel，fiber liquid and crosslinked flu? id，have been evaluated after the shape of sand banks，and the proppant settlement velocity and horizontal migration velocity were analyzed. The results show that the slick water can develop short and high sand banks，so it has the worst sand carrying capability. Crosslinked fluid can develop long and low sand banks，which is also the most gradual one，so it has the best sand carrying capability. The sand carrying capabilities of the linear gel and fiber liquid are between them. The horizontal migration velocities of proppant particles in four kinds of fracturing fluids are 78 percent，85 percent，91 percent and 95 percent of fluid velocity，and the settlement velocities from high to low are slick water，linear gel，fiber liquid and crosslinked fluid respectively. So the appropriate fracturing fluids should be chosen based on the reservoir parameters and the types of fractures in the field.
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