Volume 23,Issue 1,2016 Table of Contents
2016, 23(1):1-7.
Abstract:
After shale gas，the tight oil becomes another new target for the exploration and development of unconventional oil and gas all over the world，and it is paid more attention by domestic petroleum industry. The controversy，however，has been going on throughout the nation over the concept of the tight oil. The paper aims at defining tight oil of the Yanchang Formation in Ordos Basin，based on analysis of the tight oil in the Yanchang Formation from different perspectives including reservoir physical property and mobile fluid. The permeability boundary was determined combining with the exploration and development practice in Ordos Basin to make a discussion on the standard of definition of tight oil. The result shows that conditions for hydrocarbon reservoiring in the Yanchang Formation are good in Ordos Basin. The intervals of Chang6，Chang7，Chang8 and Chang9 are the main areas for tight oil accumulation. The central area and the south of deep lacustrine of the Yanchang Formation are most favorable for tight oil exploration in Ordos Basin. Six parameters were proposed to define the permeability boundary of tight oil based on logging，physical property，movable fluid，radius of main flow throat，threshold pressure gradient，oil viscosity，pressure coefficient and data of oil test. As a result，the classification criteria of reservoir type were modified and the upper limit of reservoir permeability of tight oil was determined as 0.5×10- 3 μm2，which is mainly suitable for tight sandstone oil and shale oil. Therefore，the concept of tight oil should be defined according to geological characteristics，practices of exploration and development in each basin.
After shale gas，the tight oil becomes another new target for the exploration and development of unconventional oil and gas all over the world，and it is paid more attention by domestic petroleum industry. The controversy，however，has been going on throughout the nation over the concept of the tight oil. The paper aims at defining tight oil of the Yanchang Formation in Ordos Basin，based on analysis of the tight oil in the Yanchang Formation from different perspectives including reservoir physical property and mobile fluid. The permeability boundary was determined combining with the exploration and development practice in Ordos Basin to make a discussion on the standard of definition of tight oil. The result shows that conditions for hydrocarbon reservoiring in the Yanchang Formation are good in Ordos Basin. The intervals of Chang6，Chang7，Chang8 and Chang9 are the main areas for tight oil accumulation. The central area and the south of deep lacustrine of the Yanchang Formation are most favorable for tight oil exploration in Ordos Basin. Six parameters were proposed to define the permeability boundary of tight oil based on logging，physical property，movable fluid，radius of main flow throat，threshold pressure gradient，oil viscosity，pressure coefficient and data of oil test. As a result，the classification criteria of reservoir type were modified and the upper limit of reservoir permeability of tight oil was determined as 0.5×10- 3 μm2，which is mainly suitable for tight sandstone oil and shale oil. Therefore，the concept of tight oil should be defined according to geological characteristics，practices of exploration and development in each basin.
2016, 23(1):8-13.
Abstract:
The structural evolution in Paleogene continental rift basin of east China and the successive sedimentary filling pattern control the trap type，the carrier system and the dynamic continuity of reservoiring，resulting in continuous reservoir distribution，ordered reservoir type and complicated hydrocarbon accumulation model characterized by vertical superposition and lateral adjacency. Through the analysis of reservoir distribution sequence of different levels of geologic unit，reservoir types in sags，second-order sequences and large-scale sedimentary systems usually distributed in an order as follows：lithologic reservoir-structural reservoir-stratigraphic reservoir. Corresponding to the macroscopic geological elements of reservoir-forming and the ordered reservoir types，the microscopic reservoir attributes，including oil-bearing saturability，displacement pressure and median pressure，show ordered-changing patterns accordingly. On the other hand，differencesexsit in reservoir distribution sequence for different levels of geologic unit of the basin，mainly include the absence of some kind of reservoir type and the unbalanced resources proportioning between different reservoir types.
The structural evolution in Paleogene continental rift basin of east China and the successive sedimentary filling pattern control the trap type，the carrier system and the dynamic continuity of reservoiring，resulting in continuous reservoir distribution，ordered reservoir type and complicated hydrocarbon accumulation model characterized by vertical superposition and lateral adjacency. Through the analysis of reservoir distribution sequence of different levels of geologic unit，reservoir types in sags，second-order sequences and large-scale sedimentary systems usually distributed in an order as follows：lithologic reservoir-structural reservoir-stratigraphic reservoir. Corresponding to the macroscopic geological elements of reservoir-forming and the ordered reservoir types，the microscopic reservoir attributes，including oil-bearing saturability，displacement pressure and median pressure，show ordered-changing patterns accordingly. On the other hand，differencesexsit in reservoir distribution sequence for different levels of geologic unit of the basin，mainly include the absence of some kind of reservoir type and the unbalanced resources proportioning between different reservoir types.
2016, 23(1):14-21.
Abstract:
Types of the heterogeneous carbonate reservoir are various and its genetic mechanism is complex. The hole，cave and fissure with different genesis，formation mechanisms and scales always develop in company，thus it is difficult to classify reservoir types only using static data（outcrop，core，logging and seismic data，etc.）. The carbonate interlayer karst reservoirs in the Lower Ordovician Yingshan Formation of the western Tazhong Ⅰ gasfield was chosen as an example，and the carbonate reservoirs in the study area were classified into three types：cavity，fracture-hole and hole mainly using dynamic data（acid fracture，well test，production test，etc.）with auxiliary of static data. Combining with seismic forward and well drilling data，the seismic reflection characteristics of the carbonate reservoir are divided into three types based on geophysical response characteristics：string beads reflection，flake reflection and messy reflection. Small caves，fractures and holes are more developed in the carbonate reservoirs with bead-like reflection，in which the fracture-hole reservoir is the main space providing liquid followed by the cave reservoir；fracture-hole and hole reservoir are the main space providing liquid with flake-like reflection and messy reflection respectively. The carbonate reservoirs with three kinds of seismic reflection developed with inheritance，the carbonate reservoirs with some messy reflections were reconstructed later strongly by burial dissolution to form carbonate reservoirs with bead-like and flake-like reflection. Besides，the oil and gas bearing characteristics of relatively tight reservoirs and its continuity were discussed preliminarily，and it is believed that the oil and gas in relative compacted segments accumulates in channels and throats in adsorbed or in free state，and the reservoirs are horizontally continuous and connected to some degree.
Types of the heterogeneous carbonate reservoir are various and its genetic mechanism is complex. The hole，cave and fissure with different genesis，formation mechanisms and scales always develop in company，thus it is difficult to classify reservoir types only using static data（outcrop，core，logging and seismic data，etc.）. The carbonate interlayer karst reservoirs in the Lower Ordovician Yingshan Formation of the western Tazhong Ⅰ gasfield was chosen as an example，and the carbonate reservoirs in the study area were classified into three types：cavity，fracture-hole and hole mainly using dynamic data（acid fracture，well test，production test，etc.）with auxiliary of static data. Combining with seismic forward and well drilling data，the seismic reflection characteristics of the carbonate reservoir are divided into three types based on geophysical response characteristics：string beads reflection，flake reflection and messy reflection. Small caves，fractures and holes are more developed in the carbonate reservoirs with bead-like reflection，in which the fracture-hole reservoir is the main space providing liquid followed by the cave reservoir；fracture-hole and hole reservoir are the main space providing liquid with flake-like reflection and messy reflection respectively. The carbonate reservoirs with three kinds of seismic reflection developed with inheritance，the carbonate reservoirs with some messy reflections were reconstructed later strongly by burial dissolution to form carbonate reservoirs with bead-like and flake-like reflection. Besides，the oil and gas bearing characteristics of relatively tight reservoirs and its continuity were discussed preliminarily，and it is believed that the oil and gas in relative compacted segments accumulates in channels and throats in adsorbed or in free state，and the reservoirs are horizontally continuous and connected to some degree.
2016, 23(1):22-30.
Abstract:
Based on a large number of experimental data analysis and microscopic observation，the systemic evaluation of origin-rich lacustrine shale in the Paleogene Shahejie Formation in the central-north area of Huanghua depression was taken to determine the formation condition and resources potential of shale gas in the area through analyzing characteristics of the shale development，organic matter abundance and type，thermal evolution degree，reservoir performance and other aspects. The results show that the cumulative thickness of the effective shale is thick（>1 000 m）；the organic matter abundance is high（>1.0%）and the organic type is moderate（mainlyⅡ1 andⅡ2）；the degree of thermal evolution is mature to higher mature，and the reservoir properties are good；these conditions are favorable for shale gas formation. The parameters of thickness of shale with rich organic matter，organic carbon content，vitrinite reflectance，buried depth and formation pressure were taken as the evaluation standards for target optimization in the area through the comparison of the main features of the shale gas in America，Chinese continent and marine. The southwest of Qikou sag and the Zhangjuhe area were selected initially as favorable areas for shale gas exploration，especially Es3 the most favorable interval for shale gas formation.The total amount of prospective resource of shale oil and gas generated from the Shahejie Formation in the central-north area of Huanghua depression is 0.46×1012 m3，of which Es3 occupies 73%. It shows enormous potential of the shale gas reseurces there.
Based on a large number of experimental data analysis and microscopic observation，the systemic evaluation of origin-rich lacustrine shale in the Paleogene Shahejie Formation in the central-north area of Huanghua depression was taken to determine the formation condition and resources potential of shale gas in the area through analyzing characteristics of the shale development，organic matter abundance and type，thermal evolution degree，reservoir performance and other aspects. The results show that the cumulative thickness of the effective shale is thick（>1 000 m）；the organic matter abundance is high（>1.0%）and the organic type is moderate（mainlyⅡ1 andⅡ2）；the degree of thermal evolution is mature to higher mature，and the reservoir properties are good；these conditions are favorable for shale gas formation. The parameters of thickness of shale with rich organic matter，organic carbon content，vitrinite reflectance，buried depth and formation pressure were taken as the evaluation standards for target optimization in the area through the comparison of the main features of the shale gas in America，Chinese continent and marine. The southwest of Qikou sag and the Zhangjuhe area were selected initially as favorable areas for shale gas exploration，especially Es3 the most favorable interval for shale gas formation.The total amount of prospective resource of shale oil and gas generated from the Shahejie Formation in the central-north area of Huanghua depression is 0.46×1012 m3，of which Es3 occupies 73%. It shows enormous potential of the shale gas reseurces there.
2016, 23(1):31-38.
Abstract:
Yining sag has good oil and gas exploration prospect and complicated tectonic conditions due to the orogeny of the North，Central and South Tianshan，so it is important to carry out research on tectonic style and its relation with oil and gas in the region. Based on comprehensive analysis，thrust faults developed in Yining sag in NW-NWW，formed in the Hercynian period，mostly activated continuously during the Indo-Chinese and Yanshan epoch and became silent in the Himalayan period. According to the characteristics of fault development and its control degree on deposition and structure，faults in the study area can be divided into three types：deep fault controlling basin，large fault controlling zone and secondary fault controlling structure. And they are combined with fold to form the fault-folded structures which include ramp and back thrust，imbricate structure，Y-type structure，flower structure and so on. According to tectonic style and structure deformation level，Yining sag from north to south can be divided into north rim strong deformation zone，Huocheng-Quluhai weak deformation zone，Cha County-Well Y2 medium deformation zone and south strong deformation zone. Yining sag experienced four evolutionary stages since Mesozoic：the large-scale fault-depression basin formed in the Indo-Chinese epoch，the formation and development of foreland basin in early-middle Yanshan epoch，the uplifting of basin as whole and imbalanced basin reformation in the late Yanshanian period，the imbalanced development of Paleogene-Neogene sediments in the Himalayan period. In the process of tectonic evolution，three sets of main hydrocarbon source rocks deposited and remained in the area，including the middle Permian Tamuqisayi Formation，the upper Triassic Baijiantan Formation and the Lower Jurassic Badaowan Formation，in which large-scale hydrocarbon expulsion happened respectively in the Indo-Chinese and Yanshan epoch and the early-late Yanshanian period. The fault fold structure zone，formed in the IndoChinese epoch，is the main pointing area for oil and gas migration and accumulation. More attention should be paid to the fault-folded structure of Y-type structure and flower structure in the Cha County-Well N4 for oil and gas exploration.
Yining sag has good oil and gas exploration prospect and complicated tectonic conditions due to the orogeny of the North，Central and South Tianshan，so it is important to carry out research on tectonic style and its relation with oil and gas in the region. Based on comprehensive analysis，thrust faults developed in Yining sag in NW-NWW，formed in the Hercynian period，mostly activated continuously during the Indo-Chinese and Yanshan epoch and became silent in the Himalayan period. According to the characteristics of fault development and its control degree on deposition and structure，faults in the study area can be divided into three types：deep fault controlling basin，large fault controlling zone and secondary fault controlling structure. And they are combined with fold to form the fault-folded structures which include ramp and back thrust，imbricate structure，Y-type structure，flower structure and so on. According to tectonic style and structure deformation level，Yining sag from north to south can be divided into north rim strong deformation zone，Huocheng-Quluhai weak deformation zone，Cha County-Well Y2 medium deformation zone and south strong deformation zone. Yining sag experienced four evolutionary stages since Mesozoic：the large-scale fault-depression basin formed in the Indo-Chinese epoch，the formation and development of foreland basin in early-middle Yanshan epoch，the uplifting of basin as whole and imbalanced basin reformation in the late Yanshanian period，the imbalanced development of Paleogene-Neogene sediments in the Himalayan period. In the process of tectonic evolution，three sets of main hydrocarbon source rocks deposited and remained in the area，including the middle Permian Tamuqisayi Formation，the upper Triassic Baijiantan Formation and the Lower Jurassic Badaowan Formation，in which large-scale hydrocarbon expulsion happened respectively in the Indo-Chinese and Yanshan epoch and the early-late Yanshanian period. The fault fold structure zone，formed in the IndoChinese epoch，is the main pointing area for oil and gas migration and accumulation. More attention should be paid to the fault-folded structure of Y-type structure and flower structure in the Cha County-Well N4 for oil and gas exploration.
2016, 23(1):39-45.
Abstract:
Diapirs are mainly secondary diapirs resulted from fault activity. But there are more syngenetic diapirs in Niger Termit Basin because early faults developed poorly. Through experimental simulation，the formation mechanism of mud diapirs in study areas is that the plastic mudstone was compressed by regional stress field which was the active force and warped up while two sides of the mudstone were loaded unevenly. According to the type of force and structural position，the mud diapirs in this area were divided into three types：faulted slope-extrusion diapir，low uplift-induced tension-differential loading diapir and sag-differential loading diapir. Impacts of diapir on hydrocarbon accumulation were mainly concluded as follows：①Uncompacted mudstone with high pressure has hydrocarbon generation potential，and the hydrocarbon will be generated after they reach into hydrocarbon generation threshold；②Diapirs penetration could improve the ability of oil and gas vertical migration and produce micro-cracks to make high-pressure fluid discharge easy；③Traps formed by diapir penetration are the anticline trap at the top of diapir and the lithologic trap at the sides of diapir；④Conditions of sands at the middle of slope near hydrocarbon-generation sag are superior to hydrocarbon accumulation，and the trap formed in this diapir penetration area is the favorable hydrocarbon accumulation zone. Exploration examples show that all wells drilled in the Cretaceous and basement near Moul sag are successful in oil test in the east faulted slope where diapir penetration developed the most.
Diapirs are mainly secondary diapirs resulted from fault activity. But there are more syngenetic diapirs in Niger Termit Basin because early faults developed poorly. Through experimental simulation，the formation mechanism of mud diapirs in study areas is that the plastic mudstone was compressed by regional stress field which was the active force and warped up while two sides of the mudstone were loaded unevenly. According to the type of force and structural position，the mud diapirs in this area were divided into three types：faulted slope-extrusion diapir，low uplift-induced tension-differential loading diapir and sag-differential loading diapir. Impacts of diapir on hydrocarbon accumulation were mainly concluded as follows：①Uncompacted mudstone with high pressure has hydrocarbon generation potential，and the hydrocarbon will be generated after they reach into hydrocarbon generation threshold；②Diapirs penetration could improve the ability of oil and gas vertical migration and produce micro-cracks to make high-pressure fluid discharge easy；③Traps formed by diapir penetration are the anticline trap at the top of diapir and the lithologic trap at the sides of diapir；④Conditions of sands at the middle of slope near hydrocarbon-generation sag are superior to hydrocarbon accumulation，and the trap formed in this diapir penetration area is the favorable hydrocarbon accumulation zone. Exploration examples show that all wells drilled in the Cretaceous and basement near Moul sag are successful in oil test in the east faulted slope where diapir penetration developed the most.
2016, 23(1):46-52.
Abstract:
Nm Ⅱ2-4 layers in Qinhuangdao32-6 oilfield are a set of far source sandy braided river reservoirs. According to river configuration classification scheme of Maill，the architecture of the braided river reservoir was analyzed. The genesis，characteristics，identification methods and the superposed pattern of all levels of configuration units were discussed. The fifth level configuration unit is the whole braided river；the fourth level configuration unit consists of three microfacies which are channel，channel bar and floodplain，and four kinds of vertical superposed models were proposed as channelbarfloodplain，channel-channel，channel-bar-channel and channel-bar-floodplain-channel，while three kinds of horizontal contact model were described as channel-beach，channel-floodplain and beach-floodplain. For the third level configuration unit，the channel was divided into bottom energy retention unit，high energy filling unit，accretion unit in the central part and waste low energy filling unit on the top of the channel. The channel bar was divided into vertical accretion body and off silt layer. Three superposed models of the third level configuration unit within the channel are retention-filling-accretion-waste-retention，retention-filling-accretion-retention and retention-filling-retention. The contact relation? ships of the vertical accretion bodies were divided into contact type and isolation type. The controlling factors of the configuration characteristics are terrain conditions，water energy，provenance supply，the ascending-descending of base levels and tectonic movements.
Nm Ⅱ2-4 layers in Qinhuangdao32-6 oilfield are a set of far source sandy braided river reservoirs. According to river configuration classification scheme of Maill，the architecture of the braided river reservoir was analyzed. The genesis，characteristics，identification methods and the superposed pattern of all levels of configuration units were discussed. The fifth level configuration unit is the whole braided river；the fourth level configuration unit consists of three microfacies which are channel，channel bar and floodplain，and four kinds of vertical superposed models were proposed as channelbarfloodplain，channel-channel，channel-bar-channel and channel-bar-floodplain-channel，while three kinds of horizontal contact model were described as channel-beach，channel-floodplain and beach-floodplain. For the third level configuration unit，the channel was divided into bottom energy retention unit，high energy filling unit，accretion unit in the central part and waste low energy filling unit on the top of the channel. The channel bar was divided into vertical accretion body and off silt layer. Three superposed models of the third level configuration unit within the channel are retention-filling-accretion-waste-retention，retention-filling-accretion-retention and retention-filling-retention. The contact relation? ships of the vertical accretion bodies were divided into contact type and isolation type. The controlling factors of the configuration characteristics are terrain conditions，water energy，provenance supply，the ascending-descending of base levels and tectonic movements.
2016, 23(1):53-60.
Abstract:
Fracture characteristics of individual wells of Keshen-2 gas field were analyzed using data of cores，thin sections and imaging logging，and interwell fractures were predicted quantitatively by stress field numerical simulation. The primary controlling factors of fracture development and the relationship between fracture and gas production were also discussed.The results demonstrate that upright and high angle shearing structural fractures with NNW-NW strike mainly develop in Keshen-2 gas field. Fracture aperture from core data are mainly between 0 and 0.2 mm，while that of microcosmic fractures are generally between 0.01 and 0.06 mm. Fractures are mainly filled by calcite，and the filling coefficient is approximately 0.63. Drilling fluid loss in the fractured zone is large，and the fracture linear density and fracture porosity are both high in fault belts which are the most favorable areas for fracture development. Fractures at the top of anticlines have low density but high aperture and porosity，and wells in these areas have high gas production，thus fractures develop well at the top of anticline in general. The increase of calcium content and the decrease of clay content are beneficial to the development of fractures. Fractures in underwater distributary channel or estuary dam develop better than those among interdistributary channels. Within the development process of fractured reservoir，reservoir protective procedures should be taken to avoid the rapid drop of production capacity.
Fracture characteristics of individual wells of Keshen-2 gas field were analyzed using data of cores，thin sections and imaging logging，and interwell fractures were predicted quantitatively by stress field numerical simulation. The primary controlling factors of fracture development and the relationship between fracture and gas production were also discussed.The results demonstrate that upright and high angle shearing structural fractures with NNW-NW strike mainly develop in Keshen-2 gas field. Fracture aperture from core data are mainly between 0 and 0.2 mm，while that of microcosmic fractures are generally between 0.01 and 0.06 mm. Fractures are mainly filled by calcite，and the filling coefficient is approximately 0.63. Drilling fluid loss in the fractured zone is large，and the fracture linear density and fracture porosity are both high in fault belts which are the most favorable areas for fracture development. Fractures at the top of anticlines have low density but high aperture and porosity，and wells in these areas have high gas production，thus fractures develop well at the top of anticline in general. The increase of calcium content and the decrease of clay content are beneficial to the development of fractures. Fractures in underwater distributary channel or estuary dam develop better than those among interdistributary channels. Within the development process of fractured reservoir，reservoir protective procedures should be taken to avoid the rapid drop of production capacity.
2016, 23(1):61-67.
Abstract:
Fundamental research on rock physics indicates that rock elastic features are essentially determined by its physical properties like mineral contents，texture，porosity，pore fluid and so on. However，rock physical properties are closely related to and affected by its sedimentary environment，process and consequent diagenesis history. Study on the influences of rock sedimentary features on its elastic parameters will be beneficial to reservoir prediction using seismic elastic parameters.Taking a fan-delta sandy conglomerate reservoir，the impacts of the rock physical parameters like lithology and pore fluid on its elastic parameters like density，velocity and modulus were analyzed systematically through rock physics analysis technique. The results show that velocity ratio of compressional and shear wave，shear wave impedance，shear modulus and μρ（the product of shear modulus and density）are sensitive to sandy conglomerate and mudstone，which can be used to predict the distribution of sandy conglomerate. The velocity ratio of compressional and shear wave and λρ（the product of Lame constant and the density）can be used to discriminate oil layer from water layer and to predict oil layer. Further research demonstrates that the correlations of velocity and impedance with rock porosity are becoming better when the multiple sedimentary cycles of stratigraphic sedimentary sequences are divided finely into single cycle. But their relationships are not linear and affected apparently by shale content.
Fundamental research on rock physics indicates that rock elastic features are essentially determined by its physical properties like mineral contents，texture，porosity，pore fluid and so on. However，rock physical properties are closely related to and affected by its sedimentary environment，process and consequent diagenesis history. Study on the influences of rock sedimentary features on its elastic parameters will be beneficial to reservoir prediction using seismic elastic parameters.Taking a fan-delta sandy conglomerate reservoir，the impacts of the rock physical parameters like lithology and pore fluid on its elastic parameters like density，velocity and modulus were analyzed systematically through rock physics analysis technique. The results show that velocity ratio of compressional and shear wave，shear wave impedance，shear modulus and μρ（the product of shear modulus and density）are sensitive to sandy conglomerate and mudstone，which can be used to predict the distribution of sandy conglomerate. The velocity ratio of compressional and shear wave and λρ（the product of Lame constant and the density）can be used to discriminate oil layer from water layer and to predict oil layer. Further research demonstrates that the correlations of velocity and impedance with rock porosity are becoming better when the multiple sedimentary cycles of stratigraphic sedimentary sequences are divided finely into single cycle. But their relationships are not linear and affected apparently by shale content.
2016, 23(1):68-73.
Abstract:
A completely new method of chemical flooding，the viscosifying emulsion-enhanced surfactant flooding technology，was put forward for extra-high temperature reservoirs. Its core part is to develop a viscosifying emulsification flooding system with good temperature resistance property，tackifying emulsion and high displacement efficiency for EOR in the extra-high temperature reservoirs. The viscosifying emulsion-enhanced surfactant（CH-13）was designed for reservoir temperatures of 90 to 130 °C，whose main performance is tackifying emulsion and the main agent is alkanolamide polyoxyethylene ether carboxylate. The results show that water soluble index increases quickly with the increase of CH-13 mass fraction in the concentration range of 2%-5%. When the water phase volume is less than 55% of the total volume，CH-13 can promote the formation of W/O emulsion whose tackifying emulsion ratio can reach 300%. The core displacement experiment showed that the oil recovery was improved by 15.8%-20.2% when emulsification/super-low IFT surfactant solutions were injected into the system alternately for several times.
A completely new method of chemical flooding，the viscosifying emulsion-enhanced surfactant flooding technology，was put forward for extra-high temperature reservoirs. Its core part is to develop a viscosifying emulsification flooding system with good temperature resistance property，tackifying emulsion and high displacement efficiency for EOR in the extra-high temperature reservoirs. The viscosifying emulsion-enhanced surfactant（CH-13）was designed for reservoir temperatures of 90 to 130 °C，whose main performance is tackifying emulsion and the main agent is alkanolamide polyoxyethylene ether carboxylate. The results show that water soluble index increases quickly with the increase of CH-13 mass fraction in the concentration range of 2%-5%. When the water phase volume is less than 55% of the total volume，CH-13 can promote the formation of W/O emulsion whose tackifying emulsion ratio can reach 300%. The core displacement experiment showed that the oil recovery was improved by 15.8%-20.2% when emulsification/super-low IFT surfactant solutions were injected into the system alternately for several times.
11 Factors effecting decompression and augmented injection by surfactant in low permeability reservoir
2016, 23(1):74-78.
Abstract:
Surfactant can achieve the purpose of decompression and augmented injection in low permeability reservoirs by reducing interfacial tension and emulsification. The effect of emulsification rate and interfacial tension on the decompression was studied through macroscopic and microscopic methods. The synergy between the interfacial tension and emulsification rate were analyzed. The results show that decompression can be reached when the interfacial tension is less than 5.25 mN/m，and the effect is more significant with the reduction of interfacial tension. If the interfacial tension reduces，oil recovery may increase；but when the interfacial tension decreases to 10-1 mN/m，impact on the oil recovery is limited. When it arrives at 10-2 mN/m，the surfactant cannot completely eliminate the additional resistance of residual oil in the flow channel yet. When the emulsification rate of the surfactant is greater than 0.11 mL/min，decompression effect is obvious. More pres?sure drop appears with the emulsification rate improving. But when it is greater than 0.42 mL/min，it has little effect on the pressure. The oil recovery increases with the emulsification rate improving until l0.21 mL/min. But when it is higher than 0.21 mL/min，higher emulsification rate has smaller effect on the oil recovery. Therefore，the emulsification rate of suitable surfactant system should be as short as possible and thus let oil emulsified completely to gain rapid expansion of sweep area.Then the interfacial tension is reduced to improve displacement efficiency at lower pressure and thus，higher oil recovery.
Surfactant can achieve the purpose of decompression and augmented injection in low permeability reservoirs by reducing interfacial tension and emulsification. The effect of emulsification rate and interfacial tension on the decompression was studied through macroscopic and microscopic methods. The synergy between the interfacial tension and emulsification rate were analyzed. The results show that decompression can be reached when the interfacial tension is less than 5.25 mN/m，and the effect is more significant with the reduction of interfacial tension. If the interfacial tension reduces，oil recovery may increase；but when the interfacial tension decreases to 10-1 mN/m，impact on the oil recovery is limited. When it arrives at 10-2 mN/m，the surfactant cannot completely eliminate the additional resistance of residual oil in the flow channel yet. When the emulsification rate of the surfactant is greater than 0.11 mL/min，decompression effect is obvious. More pres?sure drop appears with the emulsification rate improving. But when it is greater than 0.42 mL/min，it has little effect on the pressure. The oil recovery increases with the emulsification rate improving until l0.21 mL/min. But when it is higher than 0.21 mL/min，higher emulsification rate has smaller effect on the oil recovery. Therefore，the emulsification rate of suitable surfactant system should be as short as possible and thus let oil emulsified completely to gain rapid expansion of sweep area.Then the interfacial tension is reduced to improve displacement efficiency at lower pressure and thus，higher oil recovery.
2016, 23(1):79-84.
Abstract:
Preponderance flow path（PFP）leads to inefficient cycle，even invalid cycle of injected water between injection and production wells，which seriously affects the effect of waterflooding. This is the key problem to improve waterflooding recovery for middle and high permeability sandstone reservoir. For the actual oil production，the dynamic data were mined in maximum degree，and the seepage theory and mathematical methods were applied in identification and description of the PFP. Based on coring well data，seepage partition was determined and PFP between injection and production wells was identified combined with numerical simulation technology. According to invalid cycle model，high velocity non-Darcy flow equation and Carman-Kozeny equation，the parameters of PFP between injection and production wells were quantitatively described，and those in well pattern were calculated using fuzzy set theory. Taking the typical well pattern of thick oil layer in P23 delta front in the Xingliuzhong area for example，the PFPs between Well X21 and Well X11，Well X24 and Well X13 and Well X26 and Well X14 were identified respectively，and the invalid cycle volume，average pore radius and permeability were calculated，which are in good agreement with the actual，and thus the accuracy of the proposed method is verified.
Preponderance flow path（PFP）leads to inefficient cycle，even invalid cycle of injected water between injection and production wells，which seriously affects the effect of waterflooding. This is the key problem to improve waterflooding recovery for middle and high permeability sandstone reservoir. For the actual oil production，the dynamic data were mined in maximum degree，and the seepage theory and mathematical methods were applied in identification and description of the PFP. Based on coring well data，seepage partition was determined and PFP between injection and production wells was identified combined with numerical simulation technology. According to invalid cycle model，high velocity non-Darcy flow equation and Carman-Kozeny equation，the parameters of PFP between injection and production wells were quantitatively described，and those in well pattern were calculated using fuzzy set theory. Taking the typical well pattern of thick oil layer in P23 delta front in the Xingliuzhong area for example，the PFPs between Well X21 and Well X11，Well X24 and Well X13 and Well X26 and Well X14 were identified respectively，and the invalid cycle volume，average pore radius and permeability were calculated，which are in good agreement with the actual，and thus the accuracy of the proposed method is verified.
2016, 23(1):85-89.
Abstract:
In order to study microscopic displacement effect of hot water flooding on heavy oil qualitatively and quantitatively，a new method for displacement effect analysis was established which is named as“Cutout-Flatten Image”method. In oilwet micro-models，hot water flooding of heavy oil was performed separately at 75 and 90 ℃. The variation characteristic and mechanism of micro sweep efficiency，displacement efficiency and recovery efficiency were analyzed comparatively. Experimental data show that micro displacement effect is improved greatly by emulsion entrapment and emulsion entrainment in the oil-wet models. Micro sweep efficiency，displacement efficiency and recovery efficiency of hot water flooding at 90 ℃ for heavy oil are all higher than those at 75 ℃. Water-in-oil emulsion is in a few of residual brown oil films in the oil-wet micro-models. The residual oil in the swept area of hot water at 75 ℃ is large in quantity with a net-and block-shaped distribution；while that at 90 ℃ is small in quantity and it distributes in the shape of isolated island with poor continuity.
In order to study microscopic displacement effect of hot water flooding on heavy oil qualitatively and quantitatively，a new method for displacement effect analysis was established which is named as“Cutout-Flatten Image”method. In oilwet micro-models，hot water flooding of heavy oil was performed separately at 75 and 90 ℃. The variation characteristic and mechanism of micro sweep efficiency，displacement efficiency and recovery efficiency were analyzed comparatively. Experimental data show that micro displacement effect is improved greatly by emulsion entrapment and emulsion entrainment in the oil-wet models. Micro sweep efficiency，displacement efficiency and recovery efficiency of hot water flooding at 90 ℃ for heavy oil are all higher than those at 75 ℃. Water-in-oil emulsion is in a few of residual brown oil films in the oil-wet micro-models. The residual oil in the swept area of hot water at 75 ℃ is large in quantity with a net-and block-shaped distribution；while that at 90 ℃ is small in quantity and it distributes in the shape of isolated island with poor continuity.
2016, 23(1):90-95.
Abstract:
In the Middle East area，some carbonate reservoirs have characteristic of porous-type reservoir with few fractures and caves and low in permeability. Based on the fluid analysis on A oil reservoir in the Middle East，some experiments on oil displacement methods of enhanced oil recovery were carried out. The results show that immiscible displacement can enhance oil recovery because gas flooding can lead to oil volume expansion，viscosity decline and mobility improvement. Under the conditions of A oil reservoir，CO2 miscible displacement can be achieved while associated gas miscible displacement can’t be achieved.CO2 WAG miscible displacement is the most effective method and associated gas WAG immiscible displacement can improve oil recovery to a certain degree. CO2 WAG miscible displacement after water flooding significantly improved oil recovery by nearly 20%，but CO2 WAG miscible displacement after associated gas immiscible displacement only improved oil recovery by 2%. Under field conditions，the combination oil displacement method of gas immiscible and miscible displacement is not available；CO2 WAG miscible displacement after water flooding is suggested.
In the Middle East area，some carbonate reservoirs have characteristic of porous-type reservoir with few fractures and caves and low in permeability. Based on the fluid analysis on A oil reservoir in the Middle East，some experiments on oil displacement methods of enhanced oil recovery were carried out. The results show that immiscible displacement can enhance oil recovery because gas flooding can lead to oil volume expansion，viscosity decline and mobility improvement. Under the conditions of A oil reservoir，CO2 miscible displacement can be achieved while associated gas miscible displacement can’t be achieved.CO2 WAG miscible displacement is the most effective method and associated gas WAG immiscible displacement can improve oil recovery to a certain degree. CO2 WAG miscible displacement after water flooding significantly improved oil recovery by nearly 20%，but CO2 WAG miscible displacement after associated gas immiscible displacement only improved oil recovery by 2%. Under field conditions，the combination oil displacement method of gas immiscible and miscible displacement is not available；CO2 WAG miscible displacement after water flooding is suggested.
2016, 23(1):96-100.
Abstract:
In the dynamic analysis and prediction of water drive oilfield，water drive curve can be used to predict water cut and recoverable reserves and evaluate dynamic development of oilfields. Through literature research and case study of oilfield，the survey found that Yu Qitai water drive curve was more convenient and accurate on predicting oilfield water cut. In the paper of A new method for prediction of volumetric sweep efficiency in water-drive oilfield，the authors deduced a new formula of predicting the volumetric sweep efficiency based on Yu Qitai water drive curve. However，irrationality existed in the process of its derivation，it was modified in this study and a revised one was proposed. Using the development data from T21 fault block in Shengtuo oilfield，the results of the two formulas，curves showing correlation between volumetric sweep efficiency and water cut，were respectively compared with that of Chen Yuanqian’s formula derived from Type-A，Type-B and Type-C water drive curves. The result of the revised formula has very good consistency with that of Chen Yuanqian’s formula；but the result of the original formula is different from that of Chen Yuanqian’s formula，which shows its irrationality. The revised formula is not only more widely applicable for different field types，but has more reasonable and accurate calculation result，and should be popularized.
In the dynamic analysis and prediction of water drive oilfield，water drive curve can be used to predict water cut and recoverable reserves and evaluate dynamic development of oilfields. Through literature research and case study of oilfield，the survey found that Yu Qitai water drive curve was more convenient and accurate on predicting oilfield water cut. In the paper of A new method for prediction of volumetric sweep efficiency in water-drive oilfield，the authors deduced a new formula of predicting the volumetric sweep efficiency based on Yu Qitai water drive curve. However，irrationality existed in the process of its derivation，it was modified in this study and a revised one was proposed. Using the development data from T21 fault block in Shengtuo oilfield，the results of the two formulas，curves showing correlation between volumetric sweep efficiency and water cut，were respectively compared with that of Chen Yuanqian’s formula derived from Type-A，Type-B and Type-C water drive curves. The result of the revised formula has very good consistency with that of Chen Yuanqian’s formula；but the result of the original formula is different from that of Chen Yuanqian’s formula，which shows its irrationality. The revised formula is not only more widely applicable for different field types，but has more reasonable and accurate calculation result，and should be popularized.
2016, 23(1):101-106.
Abstract:
At present，Saertu oilfield is at high water cut stage and it is necessary to identify the distribution of its remaining oil. And analytical method of sealed coring well is the most intuitive and reliable one. Based on reservoir subdivision，the overall water-flooding characteristics of the main blocks and different reservoirs were analyzed according to the waterflooding characteristics of four new sealed coring wells drilled in Beierxi area of Saertu oilfield. The results show that the overall water-flooding characteristics of the reservoirs in this area are at medium degree，which indicates a great potential of the block. The water-flooding degree of the main part of channel sand is higher：primarily medium and strong. The medium and strong waterflooding mainly distributes in the middle of channel sand and the weak and non-waterflooding is on the top of channel sand. The overall water-flooding degree of the tabulated reservoir is medium and that of the untabulated reservoir is quite low. The weak and non-waterflooding distributes in the thin-layer tabulated reservoir and isolated untabulated reservoir. It indicates that the potential reservoirs mainly locate on the top of the channel sand，the middle of the channel sand，the thin-layer tabulated reservoir and isolated untabulated reservoir，which are the targets of adjustment and potential tapping in the future.
At present，Saertu oilfield is at high water cut stage and it is necessary to identify the distribution of its remaining oil. And analytical method of sealed coring well is the most intuitive and reliable one. Based on reservoir subdivision，the overall water-flooding characteristics of the main blocks and different reservoirs were analyzed according to the waterflooding characteristics of four new sealed coring wells drilled in Beierxi area of Saertu oilfield. The results show that the overall water-flooding characteristics of the reservoirs in this area are at medium degree，which indicates a great potential of the block. The water-flooding degree of the main part of channel sand is higher：primarily medium and strong. The medium and strong waterflooding mainly distributes in the middle of channel sand and the weak and non-waterflooding is on the top of channel sand. The overall water-flooding degree of the tabulated reservoir is medium and that of the untabulated reservoir is quite low. The weak and non-waterflooding distributes in the thin-layer tabulated reservoir and isolated untabulated reservoir. It indicates that the potential reservoirs mainly locate on the top of the channel sand，the middle of the channel sand，the thin-layer tabulated reservoir and isolated untabulated reservoir，which are the targets of adjustment and potential tapping in the future.
2016, 23(1):107-112.
Abstract:
During the process of drilling and gas injection in coal seam，under the external force disturbance，the axial or circumferential load on coal seam will change significantly. The pore and fracture in coal seam will change dynamically due to stress change and then the permeability of coal seam also changes dynamically with variation of gas types. Using the No.9 coal seam in Ningwu basin as the research object，the self-developed triaxial gas seepage experiment device was used to study the permeability variation of coal samples with increased confining pressure，and also the relationship between permeability-strain and stress-strain while axial press was increased to damage coal samples by using He，CH4，CO2 respectively. The results show that in the process of increasing confining pressure，at the initial stage the permeability of coal sample for He is the largest，moderate for CH4，smallest for CO2. With the increase of confining pressure，the effective stress increases and the permeability decreases. While stress is being increased to broken the coal seam at the direction of axial press，the permeability-strain curves and stress-strain curves are basically identical，but the change of permeability lags behind the change of stress and the greater the gas adsorption，the more obvious the lag effect.
During the process of drilling and gas injection in coal seam，under the external force disturbance，the axial or circumferential load on coal seam will change significantly. The pore and fracture in coal seam will change dynamically due to stress change and then the permeability of coal seam also changes dynamically with variation of gas types. Using the No.9 coal seam in Ningwu basin as the research object，the self-developed triaxial gas seepage experiment device was used to study the permeability variation of coal samples with increased confining pressure，and also the relationship between permeability-strain and stress-strain while axial press was increased to damage coal samples by using He，CH4，CO2 respectively. The results show that in the process of increasing confining pressure，at the initial stage the permeability of coal sample for He is the largest，moderate for CH4，smallest for CO2. With the increase of confining pressure，the effective stress increases and the permeability decreases. While stress is being increased to broken the coal seam at the direction of axial press，the permeability-strain curves and stress-strain curves are basically identical，but the change of permeability lags behind the change of stress and the greater the gas adsorption，the more obvious the lag effect.
2016, 23(1):113-118.
Abstract:
Oil displacement tests in etched glass micromodel，sandpacked glass model and heterogeneous parallel sandpack model were carried out to study the recovery efficiency of the remaining oil by branched-preformed particle gel（BPPG）injection after polymer flooding. The results of micromodel flooding tests show that the remaining oil after polymer flooding stays mainly in the low permeability zones and the corners of the high permeability zones. In the areas swept by polymer flooding，the remaining oil exists in the form of film and beads. The sweep efficiency can be significantly improved by B-PPG flooding because of the dynamic flow diversion function of the viscoelastic B-PPG particles that alternately plug and pass the throats of the pores. B-PPG is capable of adjusting the flow resistances of different permeability zones of a heterogeneous reservoir and preventing the injected water from channeling. An incremental oil recovery of 21.7% was obtained by B-PPG injection after polymer flooding in the sandpacked glass model test. Experimental results in heterogeneous parallel sandpack model showed that polymer slug could not effectively improve the sweep efficiency；while B-PPG exhibited a good performance in adjusting the displacement profile in the heterogeneous model. The substantial amount of the remaining oil in the low permeability zones after polymer flooding could be recovered by B-PPG flooding. In the heterogeneous parallel sandpack test，the enhanced oil recovery of B-PPG flooding after polymer flooding was 22.9%.
Oil displacement tests in etched glass micromodel，sandpacked glass model and heterogeneous parallel sandpack model were carried out to study the recovery efficiency of the remaining oil by branched-preformed particle gel（BPPG）injection after polymer flooding. The results of micromodel flooding tests show that the remaining oil after polymer flooding stays mainly in the low permeability zones and the corners of the high permeability zones. In the areas swept by polymer flooding，the remaining oil exists in the form of film and beads. The sweep efficiency can be significantly improved by B-PPG flooding because of the dynamic flow diversion function of the viscoelastic B-PPG particles that alternately plug and pass the throats of the pores. B-PPG is capable of adjusting the flow resistances of different permeability zones of a heterogeneous reservoir and preventing the injected water from channeling. An incremental oil recovery of 21.7% was obtained by B-PPG injection after polymer flooding in the sandpacked glass model test. Experimental results in heterogeneous parallel sandpack model showed that polymer slug could not effectively improve the sweep efficiency；while B-PPG exhibited a good performance in adjusting the displacement profile in the heterogeneous model. The substantial amount of the remaining oil in the low permeability zones after polymer flooding could be recovered by B-PPG flooding. In the heterogeneous parallel sandpack test，the enhanced oil recovery of B-PPG flooding after polymer flooding was 22.9%.
2016, 23(1):119-123.
Abstract:
Xinggu buried hill reservoir is a one with giant thick metamorphic rock. It has the characteristics of strong reservoir heterogeneity，developed fractures，up to 2 300 m of oil column，development through natural energy and rapid decline of oil production. It is difficult to optimize reasonable development mode for insufficient formation energy supply by water flooding. In view of dual media characteristics of the oil reservoir，the experiment process was improved，and an experiment method of soaking under various pressures for the dual media reservoir was put forward. Oil displacement by osmosis in matrix was quantified，and oil displacement mechanism of gas injection flooding was studied thoroughly according to numerical simulation research and field test analysis. The research result shows that gas injection flooding in the giant thick metamorphic rock buried hill reservoir can play a role in gravitationally flooding，gas floatation oil displacement and matrix osmosis，and greatly improve the sweep volume，which can act as a guidance for three-dimensional gas injection development design in Xinggu buried hill reservoir. The gas was mainly injected at the top with supplementary injection at the middlelow part. The role of gas floatation oil displacement can be played during gravity drive，and oil recovery efficiency has been enhanced by 15% compared with that of natural energy production.
Xinggu buried hill reservoir is a one with giant thick metamorphic rock. It has the characteristics of strong reservoir heterogeneity，developed fractures，up to 2 300 m of oil column，development through natural energy and rapid decline of oil production. It is difficult to optimize reasonable development mode for insufficient formation energy supply by water flooding. In view of dual media characteristics of the oil reservoir，the experiment process was improved，and an experiment method of soaking under various pressures for the dual media reservoir was put forward. Oil displacement by osmosis in matrix was quantified，and oil displacement mechanism of gas injection flooding was studied thoroughly according to numerical simulation research and field test analysis. The research result shows that gas injection flooding in the giant thick metamorphic rock buried hill reservoir can play a role in gravitationally flooding，gas floatation oil displacement and matrix osmosis，and greatly improve the sweep volume，which can act as a guidance for three-dimensional gas injection development design in Xinggu buried hill reservoir. The gas was mainly injected at the top with supplementary injection at the middlelow part. The role of gas floatation oil displacement can be played during gravity drive，and oil recovery efficiency has been enhanced by 15% compared with that of natural energy production.
2016, 23(1):124-128.
Abstract:
Through laboratory physical simulation and numerical simulation，enhanced oil recovery using weak gel flooding after cyclic steam stimulation was studied concerning high water cut and low recovery efficiency in heavy oil reservoir with edge and bottom water. The results of laboratory EOR research showed that compared with water flooding，the recovery of the steam stimulation was increased from 11.4% to 17.7% through oil viscosity reduction，and the recovery of the weak gelassisted steam stimulation may be increased by 18.3%. Optimal parameters were fixed after numerical simulation. The cyclic injection rate is 4 000 m3，the cyclic injection temperature is 280 ℃，and the slug size of injected gel is 0.06 PV. Based on the geological feature and exploitation characteristics of Nanpu35-2 oilfield，pilot test plan of weak gel flooding after cyclic steam stimulation was put forward. By the end of June 2014，11.2×104 m3 of weak gel was injected cumulatively and the cumulative oil production was 10.4×104 m3，and the recovery degree was predicted to increase by 2.6% in three pilot test well groups. The weak gel flooding is an effective development scheme after the cyclic steam stimulation in offshore heavy oil reservoir with edge and bottom water.
Through laboratory physical simulation and numerical simulation，enhanced oil recovery using weak gel flooding after cyclic steam stimulation was studied concerning high water cut and low recovery efficiency in heavy oil reservoir with edge and bottom water. The results of laboratory EOR research showed that compared with water flooding，the recovery of the steam stimulation was increased from 11.4% to 17.7% through oil viscosity reduction，and the recovery of the weak gelassisted steam stimulation may be increased by 18.3%. Optimal parameters were fixed after numerical simulation. The cyclic injection rate is 4 000 m3，the cyclic injection temperature is 280 ℃，and the slug size of injected gel is 0.06 PV. Based on the geological feature and exploitation characteristics of Nanpu35-2 oilfield，pilot test plan of weak gel flooding after cyclic steam stimulation was put forward. By the end of June 2014，11.2×104 m3 of weak gel was injected cumulatively and the cumulative oil production was 10.4×104 m3，and the recovery degree was predicted to increase by 2.6% in three pilot test well groups. The weak gel flooding is an effective development scheme after the cyclic steam stimulation in offshore heavy oil reservoir with edge and bottom water.
2016, 23(1):129-133.
Abstract:
The bottom water reservoir of fluvial facies in Caofeidian oilfields is a kind of important reservoir type in the Bohai sea，developed by irregular horizontal well pattern. Most of the oil reservoirs have entered into middle-high water cut stage with low recovery efficiency. It is urgent to research distribution law and main control factors of the remaining oil for guiding next overall adjustment. The lower member of GuanⅢ（NgⅢ）oil formation in Caofeidian oilfields is a main development unit with massive OIP，many production wells，small gas cap and low amplitude structure at high water cut stage.By analysis of geological data and production data，five factors controlling the distribution of remaining oil in the study area were concluded as structure factor（micromorphology of structure，faults with small fault throw and so on），interlayer of fluvial flood-plain，difference of oil-water contact，early development policy and current production well pattern. Remaining oil distribution has some regularity in the upper and the lower development units separated by the second-period interlayer.Remaining oil in the upper unit mainly distributes in the area with imperfect well pattern of oil ring. Remaining oil in the lower unit distributes mainly in areas with lower oil-water contact and imperfect well pattern of western oil reservoir，in the central region between lateral section and gas-oil contact，in the structural high part under the fourth-period interlayer and in areas near faults far away from production well.
The bottom water reservoir of fluvial facies in Caofeidian oilfields is a kind of important reservoir type in the Bohai sea，developed by irregular horizontal well pattern. Most of the oil reservoirs have entered into middle-high water cut stage with low recovery efficiency. It is urgent to research distribution law and main control factors of the remaining oil for guiding next overall adjustment. The lower member of GuanⅢ（NgⅢ）oil formation in Caofeidian oilfields is a main development unit with massive OIP，many production wells，small gas cap and low amplitude structure at high water cut stage.By analysis of geological data and production data，five factors controlling the distribution of remaining oil in the study area were concluded as structure factor（micromorphology of structure，faults with small fault throw and so on），interlayer of fluvial flood-plain，difference of oil-water contact，early development policy and current production well pattern. Remaining oil distribution has some regularity in the upper and the lower development units separated by the second-period interlayer.Remaining oil in the upper unit mainly distributes in the area with imperfect well pattern of oil ring. Remaining oil in the lower unit distributes mainly in areas with lower oil-water contact and imperfect well pattern of western oil reservoir，in the central region between lateral section and gas-oil contact，in the structural high part under the fourth-period interlayer and in areas near faults far away from production well.
2016, 23(1):134-138.
Abstract:
Tight oil reservoir is a kind of unconventional reservoir with poor permeability and well developed natural fractures. Stimulated reservoir volume（SRV）fracturing is an important means to effectively develop this kind of reservoirs. In order to study the influence of design parameters of fracture network on productivity，fractured tight oil reservoirs were divided into propped main fracture zones，fracture-network zones and unstimulated zones and the fracture-network zones were sub-divided into propped secondary fracture zone and un-propped secondary fracture zone based on the forming mechanism of fracture network. Dual pore system and single pore system were used to describe the seepage characteristics of the fracture-network zone and the unstimulated zone by taking non-Darcy seepage and stress sensitivity effect of the tight oil reservoir into consideration. Productivity model for tight oil reservoir after SRV fracturing was established，and the effects of SRV fracturing parameters on the productivity were analyzed. The research shows that the SRV fracturing can greatly improve the tight oil productivity. Tight oil reservoirs with higher productivity have larger stimulated reservoir volume and propped stimulated reservoir volume，intensive opened natural fractures，longer main fractures and higher primary and secondary fracture conductivity，but there is an optimal value.
Tight oil reservoir is a kind of unconventional reservoir with poor permeability and well developed natural fractures. Stimulated reservoir volume（SRV）fracturing is an important means to effectively develop this kind of reservoirs. In order to study the influence of design parameters of fracture network on productivity，fractured tight oil reservoirs were divided into propped main fracture zones，fracture-network zones and unstimulated zones and the fracture-network zones were sub-divided into propped secondary fracture zone and un-propped secondary fracture zone based on the forming mechanism of fracture network. Dual pore system and single pore system were used to describe the seepage characteristics of the fracture-network zone and the unstimulated zone by taking non-Darcy seepage and stress sensitivity effect of the tight oil reservoir into consideration. Productivity model for tight oil reservoir after SRV fracturing was established，and the effects of SRV fracturing parameters on the productivity were analyzed. The research shows that the SRV fracturing can greatly improve the tight oil productivity. Tight oil reservoirs with higher productivity have larger stimulated reservoir volume and propped stimulated reservoir volume，intensive opened natural fractures，longer main fractures and higher primary and secondary fracture conductivity，but there is an optimal value.
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