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考虑地层各向异性井壁稳定性研究对地质特征复杂的非常规油气储层开发意义重大,在对国内外近10年相关研究成果调研基础上对其主要进展进行了综述。影响井壁稳定性的地层各向异性因素包括:区域地应力大小、区域应力性质、岩石物理力学参数差异、井身结构、水化膨胀、微裂缝及弱层理盘角度等。详细梳理了各单因素对井壁稳定性的影响机制,地层应力系统及岩石强度对井壁稳定性的影响最大。对于具弱层理盘地层,沿不同钻井方向岩石强度差异较大;沿弱层理面地层容易发生水化膨胀,且往往微裂缝发育,井壁容易失稳,因此应采用高抑制钻井液体系或油基钻井液。在复杂地层钻井过程中,以上各单因素相伴而生,进行各单因素耦合条件下井壁稳定性分析对合理制定应对策略具有重要意义。加强考虑地层各向异性井壁稳定性基础理论、数值模拟及基于三维可视化建模的近实时井壁稳定动态模拟预测研究是该研究在未来的主要发展方向。
Considering the stratigraphic anisotropy of wellbore stability research is of great significance to the development of unconventional oil and gas reservoirs with complex geological features. Based on the investigation of relevant research results at home and abroad in recent 10 years, the main progress of the study is summarized. Stratigraphic anisotropy factors affecting the stability of the borehole wall include regional geostress, regional stress properties, differences in rock physical and mechanical parameters, wellbore structure, hydration expansion, micro-fractures and weak layer plate angle. The influence mechanism of each single factor on wellbore stability is combed in detail. The influence of formation stress system and rock strength has the greatest impact on the stability of wellbore. For weakly stratified reservoirs, rock strength varies greatly along different drilling directions; hydration and swelling are prone to occur along the strata of weak layers, and microcracks often develop and the borehole wall tends to be unstable. Therefore, a high inhibition drilling fluid system Or oil-based drilling fluid. In the complex formation drilling process, the above single factors accompanied by each single factor coupling conditions under the wellbore stability analysis to develop a reasonable strategy is of great significance. The basic theory, numerical simulation and near-real-time dynamic simulation prediction of borehole wall considering anisotropy of wellbore stability are the major development directions of this study in the future.