To explore the method of improving development effect and solving the problem of water breakthrough and water out for ultralow permeability fractured reservoirs, an indoor evaluation method of dynamic imbibition for f...To explore the method of improving development effect and solving the problem of water breakthrough and water out for ultralow permeability fractured reservoirs, an indoor evaluation method of dynamic imbibition for fracture-matrix system was established taking the Chang 8 reservoir in southern Yanchang Oilfield as a research target. Key factors for the imbibition effect were obtained, an imbibition's rate expression was obtained, a model considering the double effects of imbibition-displacement was built and optimal injection and production parameters for the research area were obtained as well. The results show that an optimum displacement rate that maximizes the oil displacement efficiency exists in the water displacing oil process, and the optimal displacing rate becomes smaller as the permeability decreases. The imbibition displacement efficiency increases as the reservoir quality index and water wettability index of rock become bigger. But the larger the initial water saturation or oil-water viscosity ratio is, the smaller the imbibition displacement efficiency is. The optimal injection-production ratio for the Chang 8 reservoir of southern Yanchang Oilfield is 0.95, and the predicted recovery is 17.2% when the water cut is 95%, it is 2.9% higher than the recovery of conventional injection-production ratio 1.2. By using the moderate water injection technique based on the double effects of imbibition-displacement mechanism, the water injection development effect for the ultra-low permeability fractured reservoirs can be improved significantly.展开更多
Based on drilling, logging, test production and dynamic monitoring data, the control effects of low-amplitude structure on hydrocarbon accumulation and development performance of ultra-low permeability reservoirs were...Based on drilling, logging, test production and dynamic monitoring data, the control effects of low-amplitude structure on hydrocarbon accumulation and development performance of ultra-low permeability reservoirs were discussed by using the methods of dense well pattern, multi-factor geological modeling, macro and micro analysis and static and dynamic analysis. The results show that the low-amplitude structure always had a significant control and influence on the distribution and accumulation of original hydrocarbon and water and the evolution trend of water flooding performance in ultra-low permeability reservoirs, and it was not only the direction of oil and gas migration, but also a favorable place for relative accumulation of oil and gas. The controlling effect of low-amplitude structure on ultra-low permeability reservoir mainly depended on its tectonic amplitude and scale;the larger the tectonic amplitude and scale, and the higher the tectonic position of the low amplitude structure, the better the reservoir characteristic parameters, oil and gas enrichment degree and development effect, and the larger the spatial scope it controlled and influenced;water cut and oil well output always fluctuated orderly with the height of the low-amplitude structure;the dynamic response of waterflooding was closely related to the relative structural position of the injection and production wells;the injected water always advanced to the low-lying area of the structure first and then moved up to the high-lying area of the structure gradually;with the continuous expansion of the flooded area, part of the oil and gas in the low-lying part of the structure was forced to be distributed to the high part of the structure, resulting in a new oil and gas enrichment, so that the dynamic reserves of oil wells in the high part increased, and the production capacity remained stable.展开更多
The global mobility theory was used to evaluate the experimental results of oil displacement with water of different salinities.The results of scanning electron microscopy,X diffraction of clay minerals,nonlinear seep...The global mobility theory was used to evaluate the experimental results of oil displacement with water of different salinities.The results of scanning electron microscopy,X diffraction of clay minerals,nonlinear seepage and nuclear magnetic resonance experiments and particle migration inhibition experiments before and after water flooding were compared to determine the mechanisms of water sensitive damage and enhanced water flooding mechanism of low permeability sandy conglomerate reservoirs in Wushi region of Beibuwan Basin,China.A production equation of the oil-water two phase flow well considering low-speed non-Darcy seepage and reservoir stress sensitivity was established to evaluate the effect of changes in reservoir properties and oil-water two-phase seepage capacity on reservoir productivity quantitatively,and injection water source suitable for the low permeability sandy conglomerate reservoirs in Wushi region was selected according to dynamic compatibility experimental results of different types of injected water.The seepage capacity of reservoir is the strongest when the injected water is formation water of 2 times salinity.The water-sensitive damage mechanisms of the reservoirs in Wushi region include hydration of clay minerals and particle migration.By increasing the content of cations(especially K+and Mg2+)in the injected water,the water-sensitive damage of the reservoir can be effectively inhibited.The formation water of Weizhou Formation can be used as the injection water source of low permeability sandy conglomerate reservoirs in the Wushi region.展开更多
It is very important to design the optimum starting time of water injection for the development of low permeability reservoirs. In this type of reservoir the starting time of water injection will be affected by a rese...It is very important to design the optimum starting time of water injection for the development of low permeability reservoirs. In this type of reservoir the starting time of water injection will be affected by a reservoir pressure-sensitive effect. In order to optimize the starting time of water injection in low permeability reservoirs, this effect of pressure change on rock permeability of low permeability reservoirs was, at first, studied by physical simulation. It was shown that the rock permeability decreases exponentially with an increase in formation pressure. Secondly, we conducted a reservoir engineering study, from which we obtained analytic relationships between formation pressure, oil production rate, water production rate and water injection rate. After our physical, theoretical and economical analyses, we proposed an approach which takes the pressure-sensitive effect into consideration and designed the optimum starting time of water injection, based on the principle of material balance. Finally, the corresponding software was developed and applied to one block of the Jiangsu Oilfield. It is shown that water injection, in advance of production, can decrease the adverse impact of the pressure-sensitive effect on low permeability reservoir development. A water-flooding project should be preferably initiated in advance of production for no more than one year and the optimum ratio of formation pressure to initial formation pressure should be maintained at a level between 1.05 and 1.2.展开更多
The development of low-permeability oil and gas resources presents a significant challenge to traditional development methods.To address the problem of“no injection and no production”in low-permeability reservoirs,a...The development of low-permeability oil and gas resources presents a significant challenge to traditional development methods.To address the problem of“no injection and no production”in low-permeability reservoirs,a novel fracture-injection-production integration technology named fracturing-flooding has been proposed by oilfield sites.This technology combines the advantages of conventional fracturing,water flooding,and chemical flooding,resulting in improved reservoir physical properties,increased injection,replenished energy,and increased oil displacement efficiency.The technology is especially suitable for low-permeability reservoirs that suffer from lack of energy,and strong heterogeneity.Fracturing-flooding technology has shown significant results and broad development prospects in some oilfields in China.This paper analyzes the development status of fracturing-flooding technology from its development history,technical mechanism,technical characteristics,process flow,types of fracturing and oil displacement fluids,and field applications.Physical and numerical simulations of fracturingflooding technology are also summarized.The results suggest that fracturing-flooding technology is more effective than conventional fracturing,water flooding,and chemical flooding in stimulating lowpermeability tight reservoirs and improving oil recovery.Moreover,it has a high input-output ratio and can be utilized for future reservoir stimulation and transformation.展开更多
Changqing old oilfield Jurassic reservoir's average calibration recovery is 24.7%,with geological reserves recovery of 16.6%,water cut of 65.2%.And most of Jurassic reservoirs are in the middle and later field lif...Changqing old oilfield Jurassic reservoir's average calibration recovery is 24.7%,with geological reserves recovery of 16.6%,water cut of 65.2%.And most of Jurassic reservoirs are in the middle and later field life,part of them has entered the high water cut and high recovery stage.Traditional water flooding way for improving oil recovery becomes more difficult,and new method has to be considered.Maling oilfield BS district is a typical representative,with high water cut of 90.8%,high recovery percent of 26.1%and low oil recovery rate of 0.25%.To explore the new way to improve oil recovery,the polymer and surfactant(SP for short)important pilot test has been developed.The low permeability reservoir indoor core data in high water cut stage and inspection well results indicate that the reservoir permeability,pore combination characteristics and pore type changed greatly after long-term water flooding development.These changes bring more difficulties to the continue development,especially the high injection pressure,which can cause other problems for well pattern infilling and EOR.This paper takes the high injection pressure problem of Maling BS district Jurassic reservoir for example,analyzes the physical property change law on the following aspects:the development mode in the past,core analysis,formation sensitivity,interstitial matter,well test interpretation results,in order to help to further effective development and provide important parameters for tertiary oil recovery technique for similar reservoirs and others.展开更多
Low-permeability dense reservoirs,including micro-fractured reservoirs,are commonly characterized by high content of clay substances,high original water saturation,high sensitivity to invasive fluids,high capillary pr...Low-permeability dense reservoirs,including micro-fractured reservoirs,are commonly characterized by high content of clay substances,high original water saturation,high sensitivity to invasive fluids,high capillary pressure,complicated structure and anisotropic,high flow-resistance and micro pore throats etc,.Generally they also have lots of natural micro fractures,probably leading to stress sensibility.Main damaging factors in such reservoirs are water-sensibility and water-blocking caused by invasive fluids during drilling and production operations.Once damaged,formation permeability can rarely recovered.Numerous studies have shown that damaging extent of water-blocking ranges from 70% to 90%.Main damaging mechanisms and influencing factors of water-blocking were systematically analyzed.Also some feasible precaution or treating approaches of water-blocking were put forward.In a laboratory setting,a new multi-functional drilling fluid composed mainly of amphion polymer,sulfonation polymer,high effectively preventive water-blocking surfactants,ideal packing temporary bridging agents(TBA) and film-forming agents,etc.,were developed.New low-damage drilling fluids has many advantages,such as good rheological properties,excellent effectiveness of water-blocking prevention,good temporary plugging effect,low filtration and ultra-low permeability(API filtration≤5 mL,HTHP filtration≤10 mL,mud cake frictional coefficient≤0.14,permeability recovery>81%),can efficiently prevent or minimize damage,preserve natural formation and enhance comprehensive development-investment effect in TUHA Jurassic dense sandstone reservoir formation with low-permeability,the only one developing integrated condense gas field.Some references can be provided to similar reservoir formations.展开更多
基金Supported by Science Coordination New Project(2016KTCL01-12)
文摘To explore the method of improving development effect and solving the problem of water breakthrough and water out for ultralow permeability fractured reservoirs, an indoor evaluation method of dynamic imbibition for fracture-matrix system was established taking the Chang 8 reservoir in southern Yanchang Oilfield as a research target. Key factors for the imbibition effect were obtained, an imbibition's rate expression was obtained, a model considering the double effects of imbibition-displacement was built and optimal injection and production parameters for the research area were obtained as well. The results show that an optimum displacement rate that maximizes the oil displacement efficiency exists in the water displacing oil process, and the optimal displacing rate becomes smaller as the permeability decreases. The imbibition displacement efficiency increases as the reservoir quality index and water wettability index of rock become bigger. But the larger the initial water saturation or oil-water viscosity ratio is, the smaller the imbibition displacement efficiency is. The optimal injection-production ratio for the Chang 8 reservoir of southern Yanchang Oilfield is 0.95, and the predicted recovery is 17.2% when the water cut is 95%, it is 2.9% higher than the recovery of conventional injection-production ratio 1.2. By using the moderate water injection technique based on the double effects of imbibition-displacement mechanism, the water injection development effect for the ultra-low permeability fractured reservoirs can be improved significantly.
基金Supported by Open Fund(PLC20190203)of State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation(Chengdu University of Technology)the Natural Science Foundation of Shaanxi Province,China(2006Z07,2010JM5003)Youth Science and Technology Innovation Fund Project of Xi’an Petroleum University(2012BS010)
文摘Based on drilling, logging, test production and dynamic monitoring data, the control effects of low-amplitude structure on hydrocarbon accumulation and development performance of ultra-low permeability reservoirs were discussed by using the methods of dense well pattern, multi-factor geological modeling, macro and micro analysis and static and dynamic analysis. The results show that the low-amplitude structure always had a significant control and influence on the distribution and accumulation of original hydrocarbon and water and the evolution trend of water flooding performance in ultra-low permeability reservoirs, and it was not only the direction of oil and gas migration, but also a favorable place for relative accumulation of oil and gas. The controlling effect of low-amplitude structure on ultra-low permeability reservoir mainly depended on its tectonic amplitude and scale;the larger the tectonic amplitude and scale, and the higher the tectonic position of the low amplitude structure, the better the reservoir characteristic parameters, oil and gas enrichment degree and development effect, and the larger the spatial scope it controlled and influenced;water cut and oil well output always fluctuated orderly with the height of the low-amplitude structure;the dynamic response of waterflooding was closely related to the relative structural position of the injection and production wells;the injected water always advanced to the low-lying area of the structure first and then moved up to the high-lying area of the structure gradually;with the continuous expansion of the flooded area, part of the oil and gas in the low-lying part of the structure was forced to be distributed to the high part of the structure, resulting in a new oil and gas enrichment, so that the dynamic reserves of oil wells in the high part increased, and the production capacity remained stable.
基金Supported by the China National Science and Technology Major Project(2016ZX05024006).
文摘The global mobility theory was used to evaluate the experimental results of oil displacement with water of different salinities.The results of scanning electron microscopy,X diffraction of clay minerals,nonlinear seepage and nuclear magnetic resonance experiments and particle migration inhibition experiments before and after water flooding were compared to determine the mechanisms of water sensitive damage and enhanced water flooding mechanism of low permeability sandy conglomerate reservoirs in Wushi region of Beibuwan Basin,China.A production equation of the oil-water two phase flow well considering low-speed non-Darcy seepage and reservoir stress sensitivity was established to evaluate the effect of changes in reservoir properties and oil-water two-phase seepage capacity on reservoir productivity quantitatively,and injection water source suitable for the low permeability sandy conglomerate reservoirs in Wushi region was selected according to dynamic compatibility experimental results of different types of injected water.The seepage capacity of reservoir is the strongest when the injected water is formation water of 2 times salinity.The water-sensitive damage mechanisms of the reservoirs in Wushi region include hydration of clay minerals and particle migration.By increasing the content of cations(especially K+and Mg2+)in the injected water,the water-sensitive damage of the reservoir can be effectively inhibited.The formation water of Weizhou Formation can be used as the injection water source of low permeability sandy conglomerate reservoirs in the Wushi region.
基金Projects 2003BA613-07-05 supported by the Program of National "Fifteen" Science and Technology 04E7029 by the CNPC Innovation Foundation
文摘It is very important to design the optimum starting time of water injection for the development of low permeability reservoirs. In this type of reservoir the starting time of water injection will be affected by a reservoir pressure-sensitive effect. In order to optimize the starting time of water injection in low permeability reservoirs, this effect of pressure change on rock permeability of low permeability reservoirs was, at first, studied by physical simulation. It was shown that the rock permeability decreases exponentially with an increase in formation pressure. Secondly, we conducted a reservoir engineering study, from which we obtained analytic relationships between formation pressure, oil production rate, water production rate and water injection rate. After our physical, theoretical and economical analyses, we proposed an approach which takes the pressure-sensitive effect into consideration and designed the optimum starting time of water injection, based on the principle of material balance. Finally, the corresponding software was developed and applied to one block of the Jiangsu Oilfield. It is shown that water injection, in advance of production, can decrease the adverse impact of the pressure-sensitive effect on low permeability reservoir development. A water-flooding project should be preferably initiated in advance of production for no more than one year and the optimum ratio of formation pressure to initial formation pressure should be maintained at a level between 1.05 and 1.2.
基金supported by the grant from the Science and Technology Cooperation Project of the CNPC-SWPU Innovation Alliance (2020CX010501)。
文摘The development of low-permeability oil and gas resources presents a significant challenge to traditional development methods.To address the problem of“no injection and no production”in low-permeability reservoirs,a novel fracture-injection-production integration technology named fracturing-flooding has been proposed by oilfield sites.This technology combines the advantages of conventional fracturing,water flooding,and chemical flooding,resulting in improved reservoir physical properties,increased injection,replenished energy,and increased oil displacement efficiency.The technology is especially suitable for low-permeability reservoirs that suffer from lack of energy,and strong heterogeneity.Fracturing-flooding technology has shown significant results and broad development prospects in some oilfields in China.This paper analyzes the development status of fracturing-flooding technology from its development history,technical mechanism,technical characteristics,process flow,types of fracturing and oil displacement fluids,and field applications.Physical and numerical simulations of fracturingflooding technology are also summarized.The results suggest that fracturing-flooding technology is more effective than conventional fracturing,water flooding,and chemical flooding in stimulating lowpermeability tight reservoirs and improving oil recovery.Moreover,it has a high input-output ratio and can be utilized for future reservoir stimulation and transformation.
文摘Changqing old oilfield Jurassic reservoir's average calibration recovery is 24.7%,with geological reserves recovery of 16.6%,water cut of 65.2%.And most of Jurassic reservoirs are in the middle and later field life,part of them has entered the high water cut and high recovery stage.Traditional water flooding way for improving oil recovery becomes more difficult,and new method has to be considered.Maling oilfield BS district is a typical representative,with high water cut of 90.8%,high recovery percent of 26.1%and low oil recovery rate of 0.25%.To explore the new way to improve oil recovery,the polymer and surfactant(SP for short)important pilot test has been developed.The low permeability reservoir indoor core data in high water cut stage and inspection well results indicate that the reservoir permeability,pore combination characteristics and pore type changed greatly after long-term water flooding development.These changes bring more difficulties to the continue development,especially the high injection pressure,which can cause other problems for well pattern infilling and EOR.This paper takes the high injection pressure problem of Maling BS district Jurassic reservoir for example,analyzes the physical property change law on the following aspects:the development mode in the past,core analysis,formation sensitivity,interstitial matter,well test interpretation results,in order to help to further effective development and provide important parameters for tertiary oil recovery technique for similar reservoirs and others.
基金Project(50574061) supported by the National Natural Science Foundation of China
文摘Low-permeability dense reservoirs,including micro-fractured reservoirs,are commonly characterized by high content of clay substances,high original water saturation,high sensitivity to invasive fluids,high capillary pressure,complicated structure and anisotropic,high flow-resistance and micro pore throats etc,.Generally they also have lots of natural micro fractures,probably leading to stress sensibility.Main damaging factors in such reservoirs are water-sensibility and water-blocking caused by invasive fluids during drilling and production operations.Once damaged,formation permeability can rarely recovered.Numerous studies have shown that damaging extent of water-blocking ranges from 70% to 90%.Main damaging mechanisms and influencing factors of water-blocking were systematically analyzed.Also some feasible precaution or treating approaches of water-blocking were put forward.In a laboratory setting,a new multi-functional drilling fluid composed mainly of amphion polymer,sulfonation polymer,high effectively preventive water-blocking surfactants,ideal packing temporary bridging agents(TBA) and film-forming agents,etc.,were developed.New low-damage drilling fluids has many advantages,such as good rheological properties,excellent effectiveness of water-blocking prevention,good temporary plugging effect,low filtration and ultra-low permeability(API filtration≤5 mL,HTHP filtration≤10 mL,mud cake frictional coefficient≤0.14,permeability recovery>81%),can efficiently prevent or minimize damage,preserve natural formation and enhance comprehensive development-investment effect in TUHA Jurassic dense sandstone reservoir formation with low-permeability,the only one developing integrated condense gas field.Some references can be provided to similar reservoir formations.
