Post-fracturing evaluation by using limited data is of great significance to continuous improvement of the fracturing programs.In this paper,a fracturing curve was divided into two stages(i.e.,prepad fluid injection a...Post-fracturing evaluation by using limited data is of great significance to continuous improvement of the fracturing programs.In this paper,a fracturing curve was divided into two stages(i.e.,prepad fluid injection and main fracturing)so as to further understand the parameters of reservoirs and artificial fractures.The brittleness and plasticity of formations were qualitatively identified by use of the statistics of formation fracture frequency,and average pressure dropping range and rate during the prepad fluid injection.The composite brittleness index was quantitatively calculated by using the energy zones in the process of fracturing.It is shown from the large-scale true triaxial physical simulation results that the complexity of fractures is reflected by the pressure fluctuation frequency and amplitude in the main fracturing curve,and combined with the brittleness and plasticity of formations,the fracture morphology far away from the well can be diagnosed.Well P,a shale gas well in SE Chongqing,was taken as an example for post-fracturing evaluation.It is shown that the shale beds are of stronger heterogeneity along the extension directions of horizontal wells,and with GR 260 API as the dividing line between brittleness and plasticity in this area,complex fracture systems tend to form in brittleness-prone formations.In Well P,half of the fractures are single fractures,so it is necessary to carry out fine subsection and turnaround fracturing so as to improve development effects.This paper provides a theoretical basis for improving the fracturing well design and increasing the effective stimulated volume in this area.展开更多
With the characteristics such as low porosity, low permeability and low gas saturation, tight sandstone reservoirs almost have no natural capacity and need to be fractured (or fracturing) for productivity. Therefore, ...With the characteristics such as low porosity, low permeability and low gas saturation, tight sandstone reservoirs almost have no natural capacity and need to be fractured (or fracturing) for productivity. Therefore, fracturing capacity prediction is very necessary. However there were so many factors, and the relations between the factor and the post-frac productivity are complex. In this study, first of all factors are concluded from the gas well stable productivity formula, then I used factor analysis to look for the main factors from the logging parameters and fracturing parameters in SULIGE area. This study could provide basal references for the gas post-frac productivity prediction in tight sandstone reservoirs.展开更多
At present,shale gas exploration and development in China is faced with some problems,such as the imperfect evaluation system of reservoir effectiveness and the limitations of reservoir evaluation system on efficient d...At present,shale gas exploration and development in China is faced with some problems,such as the imperfect evaluation system of reservoir effectiveness and the limitations of reservoir evaluation system on efficient development of shale gas.In order to improve the content and the standard of reservoir evaluation,this paper analyzed the shortcomings and challenges in the static evaluation of shale gas reservoirs on the basis of existing reservoir evaluation,and established a method for evaluating shale gas reservoir effectiveness and a scheme for classifying pore systems.Then,the dynamic evaluation parameters after shale fracturing and their effects on drainage and production measures were discussed.In addition,the potential evaluation parameters of“automatic mitigating water blocking”were studied,and a comprehensive reservoir evaluation system of“staticedynamic”combination was established.And the following research results were obtained.First,new challenges to the shale gas reservoir evaluation are emerged as the lack of in-depth study on“reservoir effectiveness,dynamic evaluation parameter system after fracturing and drainage and production measures after fracturing”,which leads to the serious lag of existing shale gas reservoir evaluation system behind production.Second,the evaluation of reservoir effectiveness is mainly presented as the evaluation on the lower limit of effective porosity,and is embodied in the influence of clay bound water and unconnected pores on the development of shale gas.Third,the development of shale gas reservoir evaluation follows the trend of refining the static reservoir evaluation parameters,defining the potential evaluation indexes of“automatic mitigating water blocking”and establishing the reservoir comprehensive evaluation system of“staticedynamic”combination.Fourth,a post-frac dynamic evaluation system is determined for the potential evaluation indexes of“automatic mitigating water blocking”(e.g.,wettability,water imbibition retention capacity,water imbibition expansion mode,expansion rate,and water imbibition cracking capacity).Fifth,a reservoir evaluation idea is put forward that“static evaluation of shale gas reservoir is the foundation and postfrac dynamic evaluation is the complement”,and a comprehensive reservoir evaluation system is established of“staticedy-namic”combination suitable for the evaluation of marine shale gas reservoirs in China.展开更多
基金Project supported by the National Natural Science Funds“Mechanism of dynamic stochastic fracture control and theory of waterless fracturing for shale formations”(Grant No.51490653)the Sinopec S&T Researches“Optimal stimulation technology for shale gas formations in Fuling Block”(Grant No.P14091)the National Major S&T Projects“Demonstration of shale gas exploration and development under normal pressure in Pengshui region”(Grant No.2016ZX05061)。
文摘Post-fracturing evaluation by using limited data is of great significance to continuous improvement of the fracturing programs.In this paper,a fracturing curve was divided into two stages(i.e.,prepad fluid injection and main fracturing)so as to further understand the parameters of reservoirs and artificial fractures.The brittleness and plasticity of formations were qualitatively identified by use of the statistics of formation fracture frequency,and average pressure dropping range and rate during the prepad fluid injection.The composite brittleness index was quantitatively calculated by using the energy zones in the process of fracturing.It is shown from the large-scale true triaxial physical simulation results that the complexity of fractures is reflected by the pressure fluctuation frequency and amplitude in the main fracturing curve,and combined with the brittleness and plasticity of formations,the fracture morphology far away from the well can be diagnosed.Well P,a shale gas well in SE Chongqing,was taken as an example for post-fracturing evaluation.It is shown that the shale beds are of stronger heterogeneity along the extension directions of horizontal wells,and with GR 260 API as the dividing line between brittleness and plasticity in this area,complex fracture systems tend to form in brittleness-prone formations.In Well P,half of the fractures are single fractures,so it is necessary to carry out fine subsection and turnaround fracturing so as to improve development effects.This paper provides a theoretical basis for improving the fracturing well design and increasing the effective stimulated volume in this area.
文摘With the characteristics such as low porosity, low permeability and low gas saturation, tight sandstone reservoirs almost have no natural capacity and need to be fractured (or fracturing) for productivity. Therefore, fracturing capacity prediction is very necessary. However there were so many factors, and the relations between the factor and the post-frac productivity are complex. In this study, first of all factors are concluded from the gas well stable productivity formula, then I used factor analysis to look for the main factors from the logging parameters and fracturing parameters in SULIGE area. This study could provide basal references for the gas post-frac productivity prediction in tight sandstone reservoirs.
基金supported by the National Natural Science Foundation of China"Characterization of the Nanopore Structure and Research on Seepage in Shale Reservoir"(No.:51674044)the Applied Basic Research Project of the Sichuan Province"Research on Intelligent Evaluation System for Key Production Zone of Marine Shale Gas(Provincial Significant Project)"(No.:2019YJ0346)+1 种基金the Significant Emerging Enginecring Project of the Sichuan Province"Research on the method of evaluating the effectiveness of fracturing the shak gas reservoir on the basis of fracturing fluid flow-back law"(No.:2019JDRC0095)the Overseas Expertise Introduction Project for Discipline Innovation(111 project)"Base of Overseas Expertise Introduction for Discipline Innovation of High-Efficiency Development of Deep-Layer Marine Shale Gas"(No.:D18016).
文摘At present,shale gas exploration and development in China is faced with some problems,such as the imperfect evaluation system of reservoir effectiveness and the limitations of reservoir evaluation system on efficient development of shale gas.In order to improve the content and the standard of reservoir evaluation,this paper analyzed the shortcomings and challenges in the static evaluation of shale gas reservoirs on the basis of existing reservoir evaluation,and established a method for evaluating shale gas reservoir effectiveness and a scheme for classifying pore systems.Then,the dynamic evaluation parameters after shale fracturing and their effects on drainage and production measures were discussed.In addition,the potential evaluation parameters of“automatic mitigating water blocking”were studied,and a comprehensive reservoir evaluation system of“staticedynamic”combination was established.And the following research results were obtained.First,new challenges to the shale gas reservoir evaluation are emerged as the lack of in-depth study on“reservoir effectiveness,dynamic evaluation parameter system after fracturing and drainage and production measures after fracturing”,which leads to the serious lag of existing shale gas reservoir evaluation system behind production.Second,the evaluation of reservoir effectiveness is mainly presented as the evaluation on the lower limit of effective porosity,and is embodied in the influence of clay bound water and unconnected pores on the development of shale gas.Third,the development of shale gas reservoir evaluation follows the trend of refining the static reservoir evaluation parameters,defining the potential evaluation indexes of“automatic mitigating water blocking”and establishing the reservoir comprehensive evaluation system of“staticedynamic”combination.Fourth,a post-frac dynamic evaluation system is determined for the potential evaluation indexes of“automatic mitigating water blocking”(e.g.,wettability,water imbibition retention capacity,water imbibition expansion mode,expansion rate,and water imbibition cracking capacity).Fifth,a reservoir evaluation idea is put forward that“static evaluation of shale gas reservoir is the foundation and postfrac dynamic evaluation is the complement”,and a comprehensive reservoir evaluation system is established of“staticedy-namic”combination suitable for the evaluation of marine shale gas reservoirs in China.
