鄂尔多斯盆地佳县地区深部煤层地应力特征及其对储层物性的控制

In-situ stress in deep coal seams and its control on reservoir physical properties in the Jiaxian area， Ordos Basin

牟朋威 李珮杰 姚艳斌 刘大锰 马立民 孙晓晓 邱勇凯

Pengwei MOU Peijie LI Yanbin YAO Dameng LIU Limin MA Xiaoxiao SUN Yongkai QIU

鄂尔多斯盆地佳县地区是深部煤层气勘探开发新区。目前该区地应力研究程度较低，地应力与煤层物性发育特征关系不明确，限制了该区煤层气高效开发。基于测井和岩心测试资料，构建了基于组合弹簧模型的测井地应力计算模型，研究了本区地应力分布特征，提出了地应力对储层裂隙、孔隙度和渗透率等的控制作用。研究结果表明，佳县地区8煤层地应力平面分布具有西高东低的特点。三向主应力具有垂向主应力（平均值56.72 MPa）>最大水平主应力（平均值41.08 MPa）>最小水平主应力（平均值37.77 MPa）特征，为正断型应力机制。侧压系数平均值为0.70，表明煤层整体处于拉张环境，有利于张性裂隙发育。煤层物性特征与各地应力参数的关系表明，研究区8煤层物性发育特征是三向主应力综合作用的结果，水平主应力起主要控制作用，煤层孔隙度和渗透率随侧压系数增大和水平主应力差减小而呈减小趋势。研究区深部煤层气含气量测试结果表明，侧压系数和水平主应力差对煤层物性发育情况具有较好的指示作用，可用于有效地识别深部煤层气地质甜点区。

JThe Jiaxian area emerges as a new target for the exploration and development of deep coalbed methane （CBM） in the Ordos Basin. However， the lack of studies on its in-situ stress and the undefined relationships between the in-situ stress and the physical properties of coal seams have hindered efficient CMB production in this area. Using data from logging and core analysis， we develop a logging-based in-situ stress calculation model as constructed by the combined spring model， investigate the in-situ stress distribution in the area and explore the controlling effects of in-situ stress on the fissures， porosity， and permeability of coal reservoirs. The results indicate that the planar distribution of the in-situ stress in the No. 8 coal seam within the Jiaxian area features high in the west and low in the east. The three principal stresses decrease in the order of vertical principal stress （averaging 56.72 MPa）， maximum horizontal principal stress （averaging 41.08 MPa）， and minimum horizontal principal stress （averaging 37.77 MPa）， suggesting a normal-faulting stress regime. The No. 8 coal seam has an average coefficient of lateral pressure of 0.70， indicating that this coal seam resides in a tensile setting overall， which creates favorable conditions for the formation of tensile fissures. The relationships between the reservoir physical properties and various in-situ stress parameters indicate that the physical properties of the No. 8 coal seam in the study area result from the combined effects of the three principal stresses， in which the horizontal principal stress play a predominant role. The porosity and permeability of the coal reservoirs trend downward with an increase in the lateral pressure coefficient and a decrease in the horizontal principal stress difference. The test results of deep CBM content in the study area indicate that the lateral pressure coefficient and the horizontal principal stress difference are reliable indicators of the physical properties of coal reservoirs， establishing them as effective tools for identifying the geologic sweet spots of deep CBM.

10.11743/ogg20240611