温度围压对低渗透砂岩孔隙度和渗透率的影响研究

 对低孔、高孔两组低渗透砂岩岩心孔隙度和渗透率在温度压力共同作用下的变化特征进行试验研究。在围压5 MPa、温度25 ℃的条件下，第一组砂岩的孔隙度变化范围为3.2%～4.6%，渗透率为0.098 8×10－3～0.191 9× 10－3 μm2；第二组砂岩的孔隙度变化范围为12.8%～14.2%，渗透率为0.176 7×10－3～0.301 3×10－3 μm2。研究结果表明，在试验采用的温度、压力变化范围(25 ℃～80 ℃，5～55 MPa)内，两组低渗透砂岩的孔隙度、渗透率都表现出了较强的压力、温度敏感性。随温度、围压升高，孔隙度、渗透率都减小，围压对渗透率的影响明显高于温度对渗透率的影响。总的趋势看，温度对孔隙度的影响高于围压对孔隙度的影响，恒定测量围压5 MPa，温度由25 ℃升高到80 ℃，低孔低渗砂岩孔隙度下降了34.7%，渗透率下降了75.1%；高孔低渗砂岩孔隙度降低了18.4%，渗透率下降了35.2%；恒定测量温度25 ℃，围压由5 MPa升高到55 MPa，低孔低渗砂岩孔隙度降低32.3%，渗透率下降了89.5%，高孔低渗砂岩孔隙度降低了4.6%、渗透率降低了77.4%。

STUDY OF TEMPERATURE AND CONFINING PRESSURE EFFECTS ON POROSITY AND PERMEABILITY IN LOW PERMEABILITY SANDSTONE

Porosity and permeability are two key parameters of reservoir rocks which have been noticed widely for their measuring conditions and methods. The effects of confining pressure and temperature on porosity and permeability are studied through two groups of low permeability sand rock samples. Under the conditions of confining pressure 5 MPa and temperature 25 ℃，porosity of the first group of sand rock sample ranges from 3.2% to 4.6%，permeability from 0.098 8×10－3 μm2 to 0.191 9×10－3 μm2. And the second one?s porosity ranges from 12.8% to 14.2%，permeability from 0.176 7×10－3 μm2 to 0.301 3×10－3 μm2. The first group sandstone rock samples from subsurface formation and the second group from outcrop formation. Experimental temperature ranges from 25 ℃(room temperature) to 80 ℃ and confining pressure varies from 5 MPa to 55 MPa. Results show that porosity and permeability are strongly sensitive to confining pressure from 5 MPa to 55 MPa and temperature from 25 ℃ to 80 ℃. Both porosity and permeability decrease with confining pressure or temperature increase. Pressure effect on permeability is much higher than temperature. Generally，temperature effect on porosity is a little higher than pressure. Keeping confining pressure constant 5 MPa，increasing temperature from 25 ℃ to 80 ℃，porosity and permeability of the first group sandstone samples decrease 34.7% and 75.1% respectively；the second group's porosity and permeability decrease 18.4% and 35.2% respectively. Keeping temperature constant 25 ℃，increasing confining pressure from 5 MPa to 55 MPa，porosity and permeability of sandstone with low porosity and low permeability decrease 32.3% and 89.5% respectively；high porosity and low permeability sandstone porosity and permeability decrease 4.6% and 77.4% respectively.