延川南区块古构造应力场特征及其反演方法

Analysis of the characters of the paleotectonic stress field and its inversion method

古构造应力控制煤层构造发育程度及其分布，影响煤层储层渗透性。通过现场对煤层及其上覆岩层中节理裂隙的实测，并应用赤平投影方法将实测节理裂隙进行分期和配套分析，研究了延川南区块构造演化规律、古构造应力场特征和古构造应力的反演方法。根据摩尔库伦破裂准则，通过共轭剪断裂破裂角的大小变化来估算古构造应力场主应力值。利用 ANSYS 有限元软件，模拟了本区两期古构造应力场分布，揭示出其古构造应力场的分布规律为：燕山期构造应力场最大主应力值由东南区域的70~80 MPa逐渐降至西北区域的20~30 MPa；喜马拉雅期构造应力场最大主应力值由东北区域的60~70 MPa逐渐降至西南区域的20 MPa。

Ancient tectonic stress controls structure development degree and distribution of seam, has important effect on reservoir permeability. By measuring actual joints and staging actual measurement joints with stereo-graphic projection method, the paper studied tectonic evolution of Yanchuannan block, features of tectonic stress field and inversion analysis method of ancient tectonic stress. Mohr Coulomb fracturing criterion gives a way to estimate value of ancient tectonic stress, which could be calculated through the changes of rupture angles of con-jugated shear joints. Two periods of tectonic stress distribution were simulated, and reflected two periods of ancient tectonic stress field distribution. The maximum principal stress value of Yanshanian tectonic stress field of 70~80 MPa in the southeast region was gradually reduced to 20~30 MPa in the northwest region, and the maximum prin-cipal stress value of Himalayan tectonic stress field of 60~70 MPa in the northeast region was gradually reduced to 20 MPa in the southwest region.