【摘要】 为了研究水合物地层钻井过程中井壁及近井地层力学稳定性的演化规律，采用ABAQUS软件建立考虑水合物相变的“热-流-固”多物理场耦合井壁稳定分析模型，通过自适应网格方法模拟地层的坍塌过程，并对不同钻井时间、钻井液温度及钻井液密度下井壁坍塌演化规律进行分析。基于分析结果建立不同钻井液温度、钻井液密度及钻井时间时的井眼扩径图版。研究结果表明：井壁坍塌会导致地层传热路径发生改变，产生更大的水合物分解范围及塑性区范围；随着钻井时间增加，井周地层塑性变形的累积及水合物分解范围的扩大会大幅加剧井壁的不稳定性；控制钻井液密度在合理范围内是维持水合物地层井壁稳定的最重要手段；适度降低钻井液温度可以降低水合物的分解范围与井眼的扩径率。可根据实际工程需要选择合适的钻井液密度、温度及钻井时间组合，为水合物地层钻井方案的选择提供理论依据。更多还原

【Abstract】 In order to study the evolution of the mechanical stability of wellbore and near-well formation during drilling in hydrate formations, secondary development was carried out to establish a heat-fluid-solid multiphysics coupling analysis model of wellbore collapse considering hydrate phase transition by using ABAQUS software.Coupled with the wellbore stability analysis model, the formation collapse process was simulated by adaptive meshing, and the evolution law of wellbore collapse at different drilling time, drilling fluid temperatures and drilling fluid densities were analyzed. Based on the analysis results, the wellbore enlarge charts at different drilling fluid temperatures, drilling densities and drilling time were established. The results show that the wellbore collapse will change the heat transfer path of the formation, leading to a larger hydrate decomposition range and plastic zone range. As the drilling time increases, the accumulation of plastic deformation around the well and the expansion of the hydrate decomposition range will greatly aggravate the instability of the well wall. Controlling the drilling fluid density within a reasonable range is the most important method to maintain the wellbore stability in hydrate formations. Moderately lowering the drilling fluid temperature can reduce the decomposition range of hydrates and the enlarge rate of the wellbore. The appropriate combination of drilling fluid density, temperature,and drilling time can be selected according to actual engineering requirements to provide theoretical basis for the selection of drilling programs in hydrate formations.更多还原