裂缝对致密砂岩储层物性及产气能力影响实验

针对低孔、低渗、低丰度的致密砂岩储层开采难度大难题,根据致密砂岩储层中裂缝发育的特点,采用人造低渗裂缝砂岩岩心物理模拟的方法,开展了裂缝参数对裂缝岩心渗透率和产气能力影响程度实验。结果表明:岩心实际渗透率与理论渗透率存在差异,并且裂缝数量和高度对岩心渗透率及产气能力影响较大,而裂缝位置对岩心渗透率及产气能力基本无影响;实际裂缝壁面粗糙并非理论模型所假设的光滑面,增加了气体流动阻力,致使裂缝岩心实测渗透率值低于理论渗透率值;当裂缝岩心基质渗透率较高时,其孔喉尺寸较大,连通性较好,气体在孔喉中渗流能力较强,裂缝改善渗流作用效果不如低渗透岩心;未贯穿裂缝对岩心渗透能力改善效果十分有限,基质部分渗透率决定了气体通过能力和产气量;增加裂缝高度和裂缝数量有利于改善岩心渗透率及产气能力。

Experiments of the effects of the fracture on the physical property and gas production capacity for the tight sandstone

Aiming at the difficult development problems of low-porosity, low-permeability and low-abundance tight sandstone reservoirs, according to the characteristics of the fracture development in the reservoirs, the experiments of the effect of the fracture parameters on the fractured core permeability and gas production capacity were carried out by using physical simulation method of the artificial low-permeability fractured sandstone core. The results show that there exists a certain difference between the actual and theoretical permeabilities for the cores, and moreover the number and height of the fractures have great influences on the core permeability and gas production capacity, while the location of the fractures has little effect on the core permeability and capacity;the roughness of the actual fracture wall is not the smooth surface assumed by the theoretical model, which increases the flow resistance of the gas and results in the lower actually measured permeability value than the theoretical permeability value for the fractured core. When the matrix permeability of the fractured core is higher, its pore throat size is rather larger, its connectivity is much better, the gas seepage ability in the pore throat is more stronger, thus the effect of improving the seepage by the fracture is rather lower than that of the low-permeability core;the effect of non-penetrated fracture on improving the core permeability is very limited, the permeability of the partial matrix determines the gas penetrating capacity and gas production;the increased fracture height and number are beneficial to improve the core permeability and gas production capacity.