预加压测试页岩含气量新方法  

A new method of pre-pressurized test on shale gas content

作　　者：姚光华 熊伟[2] 胥云[2] 王晓泉 宜伟 董卫军 杜宏宇 龚齐森 

机构地区：[1]重庆矿产资源开发有限公司,重庆401123 [2]中国石油勘探开发研究院廊坊分院,河北廊坊065007

出　　处：《石油学报》2017年第10期1189-1193,1199,共6页Acta Petrolei Sinica

基　　金：国家重大科技专项(2011ZX05018-005)资助

摘　　要：页岩含气量是页岩气藏储量计算的重要参数,对气藏评价和开发指标计算有重要意义。现场解吸是测试页岩含气量的主要方法,但由于损失气量占含气量的40%~80%,使传统方法的测试结果饱受质疑。结合国内外新的测试方法,提出了一种预加压测试页岩含气量的新方法,可以规避损失气量的计算,大幅度提高测试精度。在井场,将岩心置于高压罐内,用增压泵将甲烷注入岩心直至压力达到预定压力,在储层温度下,待压力稳定后解吸测试页岩含气量。该方法对于是否已知储层压力的不同情况,采取不同的测试流程。如果已知储层压力,预加压使岩心压力达到储层压力,解吸结果就是页岩含气量;如果储层压力未知,则可通过建立页岩含气量计算理论公式求解。测试流程为先对1个岩心开展超过吸附饱和压力的2次加压(压力均超过20 MPa)及解吸测试,然后利用理论公式和2次加压解吸结果,得到单位质量页岩内的吸附气量和任意压力下的游离气量计算公式。在后期测试出储层压力后,根据游离气计算公式,计算出该压力下的游离气量,游离气量与吸附气量之和即为页岩的含气量。Shale gas content is an important parameter for shale gas reservoir reserve estimation,which is of great significance to the evaluation of gas reservoir and the calculation of development index.Field desorption is a major method for measuring shale gas content,and the lost gas volume accounts for 40%-80% of shale gas content.However,the test results of such conventional method are quite questionable.In this study,based on the new test methods a new pre-pressurizing method was proposed to measure shale gas content,which could avoid calculating the lost gas volume and greatly increased the test accuracy.At well site,the cores were placed in a highpressure container,pressurized to a given pressure by injecting methane by booster pump;under the formation temperature,the shale gas content was desorbed and tested till the pressure stabilizes.This method adopt two different processes in two cases,i.e.,whether the formation pressure is known or not before experiment.If the formation pressure is known,the cores are pre-pressurized to reach formation pressure,and the desorption result is exactly the shale gas content.If the formation pressure is unknown,a theoretical model is established to calculate shale gas content.The test process is as below：firstly,a core is pressurized twice to exceed the adsorbed saturation pressure（over 20 MPa）for desorption test,then the desorption results of twice pressurizations are used to solve the theoretical equation and obtain the calculation equations of adsorbed gas volume for a unit mass of shale and the free gas volume under any pressure.When the formation pressure is tested later,the calculation equation of free gas is adopted to calculate the free gas volume under this pressure,and the sum of free gas volume and absorbed gas volume is equal to shale gas content.

关 键 词：页岩 含气量 损失气 吸附气 预加压 

分 类 号：TE135[石油与天然气工程—油气勘探]