准噶尔盆地新生代构造应力对石炭纪火山岩构造裂缝发育的控制

构造裂缝的发育对改善储层的储渗条件有着重要的作用,特别是火山岩这种非传统储层,构造裂缝的发育是其成为有效储层的必要条件。本文主要借助构造应力场有限元数值模拟这一成熟的方法对准噶尔盆地石炭纪火山岩构造裂缝的发育状况进行预测。其两个主要的步骤是首先对区域构造应力场进行模拟计算,然后结合岩石的强度指标判断构造裂缝的发育状况。通过对准噶尔盆地地质背景和构造演化的分析,明确了新生代构造应力场的的决定性作用和石炭纪火山岩的分布区域(划分出六个区域),建立了数值模拟的计算模型、确定了边界条件与载荷。通过二维有限元数值模拟(应用Ansys软件)得到了新生代盆地应力场的分布特征和应力值。结合岩石强度指标,对火山岩构造裂缝(张裂缝和剪裂缝)的发育进行了预测并圈出相应的区域,主要为盆地西北缘、中央坳陷中部、滴西1东部,彩参2周缘、大井-将军庙等地区,对石炭纪火山岩的油气勘探战略选区, 优化勘探部署具有重要指导意义。

Controlling of Cenozoic structural stress to the development of fractures in Carboniferous volcanic rocks, Junggar Basin

Structural fractures can strongly upgrade the reservoir quality of rocks, which is essentially important for volcanic rocks, the unconventional reservoir type. Therefore, awareness of fracture development in those rocks becomes a key point to explore and develop these plays. Employing numerical simulation based on finite element method, the study predicts the development of Cenozoic structural fracture in Carboniferous volcanic rocks, Junggar Basin. Focusing on Cenozoic stress is due to that it is the newest and dominant stress stage imposed on Carboniferous volcanic rocks since its formation. The simulation model including the geometry, mechanical properties and the load conditions is built based on geological study of the basin and 6 areas (Ⅰ- V1 and V 2) of Carboniferous volcanic rocks are blocked out. Stress field is then calculated by employing Ansys 9.0 software and the values of shear stress and tensile stress are obtained. By comparing the stress value to the strength of rocks, tensile fractures and shear fractures are predicted respectively. Finally, potential development areas of structural fractures are marked out: Most part of V1 and V2, northern part of Ⅰ , northwestern of Ⅱ and eastern part of Ⅲ and Ⅳ. This would be helpful to the exploration and development of Carboniferous strata in the basin.