基于高精度位移测量的水平差应力系数计算方法  

Calculation method of horizontal differential stress coefficient based on high-precision displacement measurement

作　　者：秦雨樵 汤华[1] 吴振君[1] Qin Yuqiao;Tang Hua;Wu Zhenjun(State Key Laboratory of Geo-mechanics and Geotechnical Engineering,Institute of Rock and Soil Mechanics,Chinese Academy of Sciences,Wuhan 430071,China;University of Chinese Academy of Sciences,Beijing 100000,China)

机构地区：[1]中国科学院武汉岩土力学研究所岩土力学与工程国家重点试验室,湖北武汉430071 [2]中国科学院大学,北京100000

出　　处：《能源与环保》2021年第3期91-97,共7页CHINA ENERGY AND ENVIRONMENTAL PROTECTION

摘　　要：地应力参数的获取对于页岩气的勘查评估以及开发工作十分重要。其中,水平差应力系数是决定地层可采性的基础参数之一。为了更为准确地确定地应力参数,克服传统应力解除法测试深度有限、解除作业时间较长、测试成功率较低的问题,提出了一种基于高精度位移测量的水平差应力系数计算方法,并采用有限元方法对公式进行验证。考虑钻井液液柱压力对维持井壁稳定性的重要作用,进一步修正公式,使其能适用于深孔有压环境下,并分析了主要误差来源,给出控制误差的方法。研究得出:通过比较理论反算结果与数值计算结果,表明推导出的公式的正确性;有限元计算表明,在岩芯直径为30 mm的条件下,环切深度达到48 mm即能达到完全应力解除的目的,与传统取芯方法相比大大减少;在同一平面布置间隔120°三处测试点,能够满足测试需要;该方法的误差来源主要包括位移测试精度、岩体不连续面存在以及岩体变形参数、钻孔形态参数精度等,并给出了相应的控制方法。这种新方法不受孔深限制,具有测试时间短、测试成功率高的特点,对于页岩气的勘查以及开发具有重要的意义。The acquisition of in-situ stress parameters is very important for shale gas exploration and development.Among them,the horizontal difference stress coefficient is one of the basic parameters to determine the formation recoverability.In order to determine the in-situ stress parameters more accurately and overcome the problems of the traditional stress relief method,such as the limited test depth,the long release time and the low test success rate,a calculation method of horizontal difference stress coefficient based on high-precision displacement measurement was proposed,and the formula is verified by the finite element method.Considering the important role of drilling fluid pressure on maintaining the stability of the wellbore,the formula was further modified to make it suitable for the deep hole pressure environment,and the main error sources were analyze,and the control error method was given.The results showed that the formula was correct by comparing the theoretical calculation results with numerical results.The finite element calculation showed that the depth of ring cutting reached 48 mm under the condition of core diameter of 30 mm can achieve the purpose of complete stress relief,which was greatly reduced compared with the traditional coring method;the test points with 120°interval arranged in the same plane can meet the test needs;the error sources of this method mainly include displacement test accuracy,the existence of discontinuity surface of rock mass,deformation parameters of rock body,and the accuracy of drilling morphology parameters,and the corresponding control methods were given.This new method was not limited by the hole depth,and has the characteristics of short test time and high success rate.It was of great significance for shale gas exploration and development.

关 键 词：地应力 页岩气勘探开发 应力解除法 有限元 水平差应力系数 

分 类 号：TP80[自动化与计算机技术—检测技术与自动化装置]