天然气水合物加热分解储层变形破坏r规律研究

摘要

Development of natural gas hydrates may lead to reservoir deformation,or environmental disasters in ex-treme case. Under such circumstances,it is necessary to determine impacts of changes in hydrate saturation,physi-cal properties of reservoir formations and ultra-static pore pressures during thermal development of natural gas hy-drate on reservoir deformation. In this way,thermal fluid-solid coupling model for deterioration of mechanical prop-erties of reservoir formations due to decomposition of hydrates can be established. In addition,programs with field variable quantum were developed by using secondary development functions of ABAQUS to facilitate numerical sim-ulation over patterns of reservoir deformation induced by hydrate thermal development in Shenhu offshore areas in South China Sea. Research results show areas with decomposition of natural gas hydrate reservoirs and deterioration of mechanical properties may expand with increases in temperatures;With no development of gas,ultra-static pore pressures of reservoir formations may distribute in parabolic configuration with distances from impacts of decomposi-tion and with the heating well as the peak. Generally speaking,high ultra-static pore pressures can be seen as the key contributor for deformation of natural gas hydrate capping formations;Extents with impacts of plastic deforma-tion of reservoir formations may expand with increases in temperatures. Firstly,these impacts may be observed a-round the contact between hydrate reservoir formation and capping formation and around the contact between such reservoir formation and underlying formation. Relevant research conclusions may provide valuable references for safe development of natural gas hydrates.%为避免开采天然气水合物导致储层变形破坏,引起环境灾害,研究加热法开采天然气水合物过程中水合物饱和度、储层物性参数、超静孔隙压力变化对储层变形破坏的影响.建立了反映水合物分解引起储层力学物性劣化规律的热流固耦合模型,基于ABAQUS二次开发功能编写场变量子程序,对南海神狐海域水合物加热开采诱导储层变形破坏规律进行数值模拟分析.结果表明:天然气水合物储层分解区和力学性质劣化区范围随温度升高呈扩大趋势;未采气条件下,储层超静孔隙压力以加热井为顶点随分解影响距离呈抛物线型分布,超静孔隙压力过大是导致天然气水合物盖层变形破坏的主要因素;储层塑性变形影响范围随温度升高逐渐扩大,先出现在水合物储层与盖层、储层与下伏层接触界面.该研究为天然气水合物安全开采提供了借鉴.