高压低温水射流作用下海底天然气水合物储层破岩过程与机理研究

Marine gas hydrates drilling is a worldwide problem and related developing technologies are looking forward to break through. This project comes up with an innovation: to cut、crush undersea natural gas hydrate reservoir by using high pressure and low temperature water jet, coupled with reverse circulation central sampling drilling technology and hydraulic transportation technology of pulp. It is expected to create an advanced drilling technology which is applied to the marine gas hydrate. Theoretical analysis, numerical simulation and experimental research are taken to establish the physical model of high pressure and low temperature flow field and research on change characteristics and rules about temperature-pressure of high pressure and low temperature flow field in the environment of gas hydrate reservoir.The heat transfer model of marine gas hydrates reservoir is built for researching the heat transfer characteristics under the impact of low temperature water jet. And the stress change law of marine gas hydrates reservoir is researched because of the impact effects of water jet and the change of temperature. Rock damage critical pressure and temperature of marine gas hydrates reservoir under the impact of low temperature water jet are determined through the experimental method. Then crushing mechanism of marine gas hydrates reservoir under the impact of low temperature water jet among coupling conditions is revealed. The decomposition rules of marine gas hydrates particles in flow field obtained combining the temperature-pressure distribution of flow field and temperature-pressure transfer characteristics and dynamic decomposition model of marine gas hydrates particles in flow field that is built through the theoretical analysis. This project results can reveal mechanism of rock fragmentation of marine gas hydrates reservoir under the impact of high pressure and low temperature water jet, which provide theoretical support for application of high pressure water jet in gas hydrates drilling and exploitation.

海底天然气水合物的钻采是世界性难题，相关开发技术亟待突破。课题提出采用高压低温水射流切割、破碎水合物储层的新思路，配合反循环中心取样法、水力输送矿浆法，可望形成适用于水合物的钻采新方法。课题采用理论分析、数值模拟和实验研究相结合的方法，建立高压低温流场的物理模型，研究水合物储层环境中高压低温流场温度、压力的变化特征及规律；建立水合物储层内部的传热模型，研究低温射流作用下水合物储层的传热特性，探索储层内部由于射流冲击和温度变化而引起的应力变化规律；实验分析射流作用下水合物储层破岩临界压力和温度，揭示多场耦合条件下水合物储层在高压低温水射流冲击作用下的破碎机理；建立流场中水合物颗粒的动态分解模型，结合流场的温压分布和水合物颗粒内部的温压传递特性，得到流场中水合物颗粒的分解规律。课题成果将揭示高压低温水射流对水合物储层的破岩机理，为高压水射流在水合物钻采中的应用提供相关的理论依据。

海洋天然气水合物的钻采是世界性难题，相关开发技术亟待突破。项目提出采用高压低温水射流切割破碎水合物储层的新思路，其关键科学问题包括复杂温压条件下的射流与储层间的热传递过程、水射流破坏含水合物沉积物机理、水合物颗粒在流场中与储层中的稳定性。项目根据各关键问题特点，采用理论研究、数值模拟与物理过程模拟实验互补的研究方法，获得了水合物破碎过程中储层与流场中的温度场、压力场的特征及变化规律；阐明了高压低温水射流破碎切割水合物的过程与机理；评价了储层及流场中水合物颗粒的稳定性。取得的一系列研究成果可为高压水射流开采水合物的应用提供理论支撑与技术指导，有望形成一套高效率、低成本的特色水合物开采工艺，推动我国海洋天然气水合物开采核心技术发展，加快我国海洋天然气水合物的商业化开发进程。