Shale gas reservoirs have poor physical properties and a large number of micro-nano pores have been developed.Shale gas wells have no natural productivity and need fracturing reconstruction measures to put into produc...Shale gas reservoirs have poor physical properties and a large number of micro-nano pores have been developed.Shale gas wells have no natural productivity and need fracturing reconstruction measures to put into production.However,the fracturing fluid will enter the reservoir space of shale matrix after fracturing and affect the production of shale gas.At present,there is no consensus on the influence of fracturing fluid retention on gas well production.Based on this,the paper adopts gas molecular transport analyzer to carry out experimental research on the influence of fracturing fluid on shale gas diffusion law after entering matrix pores.The results show that:(1)Compared with the diffusion capacity of single-phase shale gas,the diffusion capacity of shale gas decreases significantly when fracturing fluid is present in the reservoir;(2)In the process of fracturing fluid flowback,when the water saturation in the reservoir decreases from 50%to 0,the gas well productivity increases by about 60%.(3)When fracturing fluid exists in the reservoir,the pore diameter has an exponential relationship with the shale gas diffusion coefficient,and the diffusion coefficient increases exponentially with the increase of pore diameter.The research of this paper provides theoretical basis for guiding the efficient development of shale gas wells.展开更多
Free granite blocks with size of 50 × 50 × 50 mm cubic form which were uniaxial compressed and pre treated as dry, water and Na 2SO 4 solution soaked, were experienced three freeze thaw stages of differe...Free granite blocks with size of 50 × 50 × 50 mm cubic form which were uniaxial compressed and pre treated as dry, water and Na 2SO 4 solution soaked, were experienced three freeze thaw stages of different temperature ranges. The temperature cycles were given and carried out in an environmental cabinet while the temperatures on the samples surface and inside 10 mm and 25 mm depth were recorded respectively. Samples' weight and ultrasonic transfer velocity were also measured before and after experiment. The results showed that, to these small free samples, there was no apparent temperature difference between those on the surface and inside the blocks. Rock temperatures varied with those of freeze thaw cycles but appeared 'relative stable' when temperatures within the total range of the cycles were below 0 ℃. The weight losses of samples were very small, but still suggested that the biggest change occurred in the group of the water soaked samples. Ultrasonic transfer velocity, to most samples, turned to be slow, specially those cross the microfractures of the samples had more change than those 'average ones'. These suggested that the internal pore volume of the samples probably enlarged and microfractures had apparent influence during the freeze thaw processes.展开更多
基金supported by the Science and Technology Innovation Foundation of CNPC“Multiscale Flow Law and Flow Field Coupling Study of Tight Sandstone Gas Reservoir”(2016D-5007-0208)13th Five-Year National Major Project“Multistage Fracturing Effect and Production of Fuling Shale Gas Horizontal Well Law Analysis Research”(2016ZX05060-009).
文摘Shale gas reservoirs have poor physical properties and a large number of micro-nano pores have been developed.Shale gas wells have no natural productivity and need fracturing reconstruction measures to put into production.However,the fracturing fluid will enter the reservoir space of shale matrix after fracturing and affect the production of shale gas.At present,there is no consensus on the influence of fracturing fluid retention on gas well production.Based on this,the paper adopts gas molecular transport analyzer to carry out experimental research on the influence of fracturing fluid on shale gas diffusion law after entering matrix pores.The results show that:(1)Compared with the diffusion capacity of single-phase shale gas,the diffusion capacity of shale gas decreases significantly when fracturing fluid is present in the reservoir;(2)In the process of fracturing fluid flowback,when the water saturation in the reservoir decreases from 50%to 0,the gas well productivity increases by about 60%.(3)When fracturing fluid exists in the reservoir,the pore diameter has an exponential relationship with the shale gas diffusion coefficient,and the diffusion coefficient increases exponentially with the increase of pore diameter.The research of this paper provides theoretical basis for guiding the efficient development of shale gas wells.
文摘Free granite blocks with size of 50 × 50 × 50 mm cubic form which were uniaxial compressed and pre treated as dry, water and Na 2SO 4 solution soaked, were experienced three freeze thaw stages of different temperature ranges. The temperature cycles were given and carried out in an environmental cabinet while the temperatures on the samples surface and inside 10 mm and 25 mm depth were recorded respectively. Samples' weight and ultrasonic transfer velocity were also measured before and after experiment. The results showed that, to these small free samples, there was no apparent temperature difference between those on the surface and inside the blocks. Rock temperatures varied with those of freeze thaw cycles but appeared 'relative stable' when temperatures within the total range of the cycles were below 0 ℃. The weight losses of samples were very small, but still suggested that the biggest change occurred in the group of the water soaked samples. Ultrasonic transfer velocity, to most samples, turned to be slow, specially those cross the microfractures of the samples had more change than those 'average ones'. These suggested that the internal pore volume of the samples probably enlarged and microfractures had apparent influence during the freeze thaw processes.
