改进的压力衰竭法测试页岩孔渗参数

Improved pressure depletion method measure the porosity and permeability of shale

非常规油气藏(如页岩气、煤层气和致密砂岩油气等)的渗透率很低,采用常规方法不易进行测试和评价。因此,提出了一种改进的压力衰竭法,用来测试致密岩样的渗透率和孔隙度,其原理是采用一较小体积的气源容器,在岩样一端施加一个较高的压力,测试系统压力的衰竭过程,通过不同压力和时间内的衰减压差,计算岩心的渗透率和孔隙度。对测试原理进行了分析,并给出孔隙度和渗透率计算模型,同时测试分析典型致密页岩岩样的压力衰竭规律,研究不同因素(气体组分、温度、围压和驱替压力)对压力衰减规律和渗透率的影响。对一页岩岩样根据实验结果计算了不同测试条件下的渗透率值,计算结果表明,随着温度及围压的升高,渗透率均降低,表明温度和围压对渗透率测量结果有重要的影响。渗透率实验测量结果与现场测试结果对比,两者数量级保持一致,表明实验方法可靠。

The permeability of unconventional reservoirs is low,such as shale gas,coal-bed methane and tight gas.It is difficult to measure the permeability by the conventional method.Therefore,a method using the improved pressure depletion to measure the porosity and permeability of tight rock is proposed.The principle is to use a smaller volume gas container with a high pressure applied to one end of the rock sample and then record the process of pressure depletion.According to the variation of pressure with time,calculate the permeability and porosity of core.Therefore,the test principle is analyzed and the computational model for porosity and permeability is established,the pressure depletion rule of the typical compact shale rock samples is tested,and the effects of different factors(gas composition,temperature,confining pressure and displacement pressure)on pressure depletion and permeability are studied.The permeability values of a shale sample under different test conditions are calculated according to the experimental results.Permeability calculation results show that the permeability decreases with the increase of temperature or confining pressure,which prove that the temperature and confining pressure have important effects on permeability measurement results.Compared with the field test results,it is found that the permeability test results are consistent with it,indicating that the experimental method is reliable.