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
Coalbeds are characterized by high organic matter content,presence of joints and smooth joint surface,which lead to weak bonding between coal and set cement and poor cementing quality of coalbeds,and consequently the ...Coalbeds are characterized by high organic matter content,presence of joints and smooth joint surface,which lead to weak bonding between coal and set cement and poor cementing quality of coalbeds,and consequently the economic and effective development of coalbed methane(CBM)is restricted seriously.In this paper,components,compositions and wetting characteristics of coal were analyzed in order to improve the water wettability of coal,the effects of different surfactants and their concentration and soaking time on the surface wetting angle of coal and interfacial bonding strength were tested and measured.The high-efficiency hydrophilic wettability modifier was optimized.The strengthened coalbed bonding prepad fluid system was developed and applied practically in the Qinshui Basin,Shanxi province.The results of laboratory tests and field applications show that the compact adsorption of surfactant containing ether and sulfate radical on the surface of coal can convert the surface wettability into strong hydrophilicity at the concentration of 0.3%within 30 s,thus improving significantly the interface bonding strength(up to 65.5%)between coal and set cement.The field application in CBM well cementing shows that the strengthened coalbed bonding prepad fluid can improve the cementing quality from unqualified level to high level,and play a significant role in improving CBM hole interval cementing quality.It is concluded that this technology provides an effective guarantee for coalbed cementing quality improvement and smooth implementation of stimulation measures like fracturing.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Coalbeds are characterized by high organic matter content,presence of joints and smooth joint surface,which lead to weak bonding between coal and set cement and poor cementing quality of coalbeds,and consequently the economic and effective development of coalbed methane(CBM)is restricted seriously.In this paper,components,compositions and wetting characteristics of coal were analyzed in order to improve the water wettability of coal,the effects of different surfactants and their concentration and soaking time on the surface wetting angle of coal and interfacial bonding strength were tested and measured.The high-efficiency hydrophilic wettability modifier was optimized.The strengthened coalbed bonding prepad fluid system was developed and applied practically in the Qinshui Basin,Shanxi province.The results of laboratory tests and field applications show that the compact adsorption of surfactant containing ether and sulfate radical on the surface of coal can convert the surface wettability into strong hydrophilicity at the concentration of 0.3%within 30 s,thus improving significantly the interface bonding strength(up to 65.5%)between coal and set cement.The field application in CBM well cementing shows that the strengthened coalbed bonding prepad fluid can improve the cementing quality from unqualified level to high level,and play a significant role in improving CBM hole interval cementing quality.It is concluded that this technology provides an effective guarantee for coalbed cementing quality improvement and smooth implementation of stimulation measures like fracturing.
