渤中25-1低渗透油田地应力分布特征及对开发的影响

DISTRIBUTION OF THE PRESENT STRESS IN LOW PERMEABILITY OILFIELD OF BOZHONG 25-1 AND ITS EFFECT ON DEVELOPMENT

利用有限元方法,对渤中25-1低渗透油田现今地应力状态进行数值模拟研究,并结合低渗透储层地质特征,分析地应力对油田开发的影响。数值模拟结果表明,渤中25-1低渗透油田沙二和沙三段的现今地应力为压应力,以北东东—南西西向为水平最大主应力的主要优势方位,地应力在平面上受断层、构造起伏和沉积微相控制明显。根据地应力状态,分析研究区的人工压裂裂缝为垂直裂缝。在远离断层的断块中部,人工压裂缝的展布方向主要为北东东—南西西方向;在断层附近,由于水平最大主应力方向发生偏转,人工压裂缝的延伸方向也会发生一定偏转,部署开发井网时需要根据断层附近地应力的实际分布规律进行相应调整。

Based on the finite element method,numerical simulation on the state of present stress in Bozhong 25-1 oilfield which is the first low permeability oilfield carried out to be.developed by CNOOC is studied.Combined with the geological characteristics,the impact of the stress on development is analyzed.It is showed that the stresses in the second and the third member of Shahezi Formation are pressure stresses and the direction of the maximum principle stress is mainly NEE-SWW.The stress is controlled by fault,structural relief and sedimentary microfacies on the plane.According to the state of the stress,the artificial fractures are vertical fracture in this area;the direction of the stress is seriously deflected near the fault,which causes the deflection of the extension direction of artificial fractures.Therefore,some adjustments should be made near the fault based on the actual distribution of stress,when the development well patterns are arrangement.