关键词: 低渗透致密砂岩, 渗透率, 有效应力, 有效应力系数, 响应面法, 修正的析因设计

Abstract: Laboratory study on the effective stress of low-permeability sandstone rock was carried out using the modified factorial design program.The design program includes several cycles under the conditions of loading and unloading confining stress at constant pore-pressure.The experimental data were collected with the steady-state method and analyzed with the response-surface method.The analysis results showed that the permeability and the effective-stress coefficient decreased as increasing confining stress and increased as increasing pore-pressure.The maximum of the effective coefficient is below 0.88 in the range of experiment condition.The effective stress coefficient is far less than 1.0 at high stress and low pressure of fluid flow in pores,which suggests that the pore pressure has a small effect on permeability.The relationship between permeability and effective stress was established.The value of effective stress was determined by using the effective stress coefficient obtained from the response-surface method.It is agreeable with the traditional concept of effective stress.

Key words: low-permeability sandstone rock, permeability, effective stress, effective-stress coefficient, response-surface method, modified factorial design program