Casing deformation and frac-hit pose significant challenges to the development of deep shale gas in southern Sichuan Basin.By analyzing the mechanism and main control factors of casing deformation and frac-hit,two kin...Casing deformation and frac-hit pose significant challenges to the development of deep shale gas in southern Sichuan Basin.By analyzing the mechanism and main control factors of casing deformation and frac-hit,two kinds of risk assessment methods were defined,and the overall prevention and control concept and practice were formulated.The results show that initial stress,pore pressure,fault development and large scale fracturing in local block are the main factors leading to the deformation.The development of fracture through well group and uncontrolled fracturing fluid volume are the main factors leading to pressure channeling.Based on this,the risk classification technology of casing deformation and frac-hit is established,and the dual-optimal,dual-control concept and technology are formed.In terms of the prevention and control of casing deformation,the formation of small-diameter bridge plug fracturing,large section combined fracturing,glass beads cementing,singlewell staggered and platform straddle fracturing mode,dual-dimension controlled and lift fracturing,hyperbolic diagnosis,etc.Frac-hit prevention and control formed pump sequence optimization mode,physical and chemical temporary plugging and other methods.The above technology achieved casing deformation rate decreased from 50.4%to 25.4%,frac-hit rate decreased from 58.6%to 33.9%,and the average well kilometer EUR reached 0.52e0.7 million square meters,an increase of 7.7%compared with the previous research,with remarkable results.展开更多
During volume fracturing of shale gas reservoirs,hydraulic fractures may readily communicate with natural fractures to propagate forward and induce the formations to slip along the fracture surfaces.The resulted inter...During volume fracturing of shale gas reservoirs,hydraulic fractures may readily communicate with natural fractures to propagate forward and induce the formations to slip along the fracture surfaces.The resulted inter-well frac-hit and casing deformation affect the safe and efficient operation of shale gas fracturing.In addition,unpropped fractures caused by small natural fracture width lead to deteriorating fracture conductivity,which in turn impacts the stimulation effect of shale gas reservoirs.This paper discusses the three key issues,i.e.inter-well frac-hit,casing deformation and unpropped microfractures,that impact the economic exploration and exploitation of shale gas,and proposes engineering prevention and control measures through literature review and research on mechanism by integrating theoretical and experimental analysis,which have been applied on site.Firstly,after clarifying the mechanism and main controlling factors of inter-well frac-hit,an evaluation model and prediction method of frac-hit based on machine learning were established.The measures for preventing and controlling inter-well frac-hit,including temporary plugging at fracture tip and shut-in of old wells,were determined after evaluation with the well-cluster fracture model.Secondly,an analysis model of casing deformation caused by fracture shear and slippage was established after stress analysis.According to the analysis of stress on casing intersected with fractures during fracturing,it is ascertained that increase of fluid pressure within natural fractures is the main factor that causes casing deformation.The methods for preventing casing deformation were proposed in terms of fracturing operation and well construction.Thirdly,the mechanism of micro-proppant migration was analyzed by integrating the model of particle migration and the transport experiment in large-scale plate,and the experiment confirms that micro-proppant can effectively improve the fracture conductivity.It is concluded after field application that the prevention and control measures proposed for inter-well frac-hit and casing deformation can mitigate frac-hit and casing deformation significantly,and micro-proppants are conducive to improving post-frac shale gas production.The measures provide a support for large-scale and economic development of deep shale gas.展开更多
So far,large-scale development of shale gas wells above 3500 m in the Changning Block of the Sichuan Basin has been realized by means of the large-scale hydraulic fracturing technology.As the main process parameters a...So far,large-scale development of shale gas wells above 3500 m in the Changning Block of the Sichuan Basin has been realized by means of the large-scale hydraulic fracturing technology.As the main process parameters arefinally set,however,the improvement rate of its stimulation effect tends to slow down,while in North America,single-well production has increased significantly by shortening cluster spacing and increasing proppant volumes.In order to provide a reliable practice basis for optimizing the parameters of shale gas fracturing process,this paper analyzes the productivity increasing mechanism of the new fracturing technology of intensive stageþhigh-intensity proppant injection by virtue of the model for calculating induced stress and multi-stage and multi-cluster productivity of horizontal wells.And accordingly,the main en-gineering factors of fracturing stimulation technology were ascertained.Then,after the pilot test scheme on this new fracturing technology was formulated according to the geological parameters of this block,the pilot test was carried out.Finally,the fracturing process parameters were optimized based on actual production effects and experimental results.And the following research results were obtained.First,shortening the spacing between main fractures,increasing the interference degree of induced stress and improving the stimulation degree of hydraulic fractures to shale reservoirs are the technical keys to the intense stage,and increasing the proppant volume,reducing the influence degree of proppant embedding and breaking on the attenuation of fracture conductivity and ensuring the long-term conductivity of propped fractures are the internal causes of significant production increase through high-intensity proppant injection.Second,the optimized implementation parameters of this new process in the Changning Block are as follows.The cluster spacing is in the range of 15e20 m,the proppant injection intensity is 2.0e2.5 t/m,and the liquid consuming intensity is 30e35 m3/m.It is concluded that this new process increases the single-well production of shale gas wells and the development benefit of the Changning Block and provides technical support for improving the comprehensive development benefit of shale gas wells in this block.展开更多
文摘Casing deformation and frac-hit pose significant challenges to the development of deep shale gas in southern Sichuan Basin.By analyzing the mechanism and main control factors of casing deformation and frac-hit,two kinds of risk assessment methods were defined,and the overall prevention and control concept and practice were formulated.The results show that initial stress,pore pressure,fault development and large scale fracturing in local block are the main factors leading to the deformation.The development of fracture through well group and uncontrolled fracturing fluid volume are the main factors leading to pressure channeling.Based on this,the risk classification technology of casing deformation and frac-hit is established,and the dual-optimal,dual-control concept and technology are formed.In terms of the prevention and control of casing deformation,the formation of small-diameter bridge plug fracturing,large section combined fracturing,glass beads cementing,singlewell staggered and platform straddle fracturing mode,dual-dimension controlled and lift fracturing,hyperbolic diagnosis,etc.Frac-hit prevention and control formed pump sequence optimization mode,physical and chemical temporary plugging and other methods.The above technology achieved casing deformation rate decreased from 50.4%to 25.4%,frac-hit rate decreased from 58.6%to 33.9%,and the average well kilometer EUR reached 0.52e0.7 million square meters,an increase of 7.7%compared with the previous research,with remarkable results.
文摘During volume fracturing of shale gas reservoirs,hydraulic fractures may readily communicate with natural fractures to propagate forward and induce the formations to slip along the fracture surfaces.The resulted inter-well frac-hit and casing deformation affect the safe and efficient operation of shale gas fracturing.In addition,unpropped fractures caused by small natural fracture width lead to deteriorating fracture conductivity,which in turn impacts the stimulation effect of shale gas reservoirs.This paper discusses the three key issues,i.e.inter-well frac-hit,casing deformation and unpropped microfractures,that impact the economic exploration and exploitation of shale gas,and proposes engineering prevention and control measures through literature review and research on mechanism by integrating theoretical and experimental analysis,which have been applied on site.Firstly,after clarifying the mechanism and main controlling factors of inter-well frac-hit,an evaluation model and prediction method of frac-hit based on machine learning were established.The measures for preventing and controlling inter-well frac-hit,including temporary plugging at fracture tip and shut-in of old wells,were determined after evaluation with the well-cluster fracture model.Secondly,an analysis model of casing deformation caused by fracture shear and slippage was established after stress analysis.According to the analysis of stress on casing intersected with fractures during fracturing,it is ascertained that increase of fluid pressure within natural fractures is the main factor that causes casing deformation.The methods for preventing casing deformation were proposed in terms of fracturing operation and well construction.Thirdly,the mechanism of micro-proppant migration was analyzed by integrating the model of particle migration and the transport experiment in large-scale plate,and the experiment confirms that micro-proppant can effectively improve the fracture conductivity.It is concluded after field application that the prevention and control measures proposed for inter-well frac-hit and casing deformation can mitigate frac-hit and casing deformation significantly,and micro-proppants are conducive to improving post-frac shale gas production.The measures provide a support for large-scale and economic development of deep shale gas.
基金supported by the National Major Science and Technology Project"Changning-Weiyuan Shale Gas Development Demonstration Project"(No.:2016ZX05062)PetroChina Major Science and Technology Project"Research and Application of Key Technologies in Gas Production of 30 billion cubic meters in Southwest Oil&Gas Field Company"(No.:2016E-0612).
文摘So far,large-scale development of shale gas wells above 3500 m in the Changning Block of the Sichuan Basin has been realized by means of the large-scale hydraulic fracturing technology.As the main process parameters arefinally set,however,the improvement rate of its stimulation effect tends to slow down,while in North America,single-well production has increased significantly by shortening cluster spacing and increasing proppant volumes.In order to provide a reliable practice basis for optimizing the parameters of shale gas fracturing process,this paper analyzes the productivity increasing mechanism of the new fracturing technology of intensive stageþhigh-intensity proppant injection by virtue of the model for calculating induced stress and multi-stage and multi-cluster productivity of horizontal wells.And accordingly,the main en-gineering factors of fracturing stimulation technology were ascertained.Then,after the pilot test scheme on this new fracturing technology was formulated according to the geological parameters of this block,the pilot test was carried out.Finally,the fracturing process parameters were optimized based on actual production effects and experimental results.And the following research results were obtained.First,shortening the spacing between main fractures,increasing the interference degree of induced stress and improving the stimulation degree of hydraulic fractures to shale reservoirs are the technical keys to the intense stage,and increasing the proppant volume,reducing the influence degree of proppant embedding and breaking on the attenuation of fracture conductivity and ensuring the long-term conductivity of propped fractures are the internal causes of significant production increase through high-intensity proppant injection.Second,the optimized implementation parameters of this new process in the Changning Block are as follows.The cluster spacing is in the range of 15e20 m,the proppant injection intensity is 2.0e2.5 t/m,and the liquid consuming intensity is 30e35 m3/m.It is concluded that this new process increases the single-well production of shale gas wells and the development benefit of the Changning Block and provides technical support for improving the comprehensive development benefit of shale gas wells in this block.
