The controlling effects of fractures on gas accumulation and production in tight sandstone: a case of jurassic dibei gas reservoir in the east kuqa foreland basin

Taking Dibei tight sandstone gas reservoir in the east Kuqa Foreland Basin as an example, this paper provides a detailed discussion of how fractures to affect the storage space and gas flow capacity, and thus how to control gas accumulation, enrichment and prolific production in tight sandstone reservoir. According to the statistics of laser confocal fluorescent microscopy observation, the micro-structural fracture width in Dibei gas reservoir is mainly in 8-25μm and the associated micro-fractures width is mainly in 4-10μm, while throat radius are mainly in 1-4μm. The fractures width is much wider than throat radius and serves as a main channel of gas flowing. Based on physical simulation experiment of gas charging into core samples with saturated water, mercury injection and gas-water two-phase permeability experiment, it illustrated that the fractures developed samples are easier for gas to flow under equal porosity condition, because of the lower expulsion pressure, higher mercury injection saturation and increased gas relative permeability. Based on these analyses, it had been deduced that the fractures control tight gas in many aspects: (1)Fractures play a significant role in reservoir property improvement. The isolated pores are linked by fractures to form connective reservoir spaces, and the solutions are prior to occur along the fractures forming new pores, and the fractures mostly with width bigger than the throat radius can provide reservoir space themselves. (2)Fractures can increase fluid flow capacity because fractures will decrease the starting pressure gradient, increase gas effective permeability and thus improve gas injection efficiency as well as gas production. (3)The fractures developed in different time and spatial places have different effects on gas accumulation, enrichment and production in tight sandstone reservoirs. ©, 2015, Science Press. All right reserved.