水合物分解诱导效应与有效应力效应耦合作用下的海域泥质粉砂型储层渗透率变化预测  

Prediction of permeability change of marine muddy silty sand reservoirs under the coupling effect of hydrate decomposition induction effect and effective stress effect

作　　者：姚艳斌[1,2] 雷欣 罗万静 陆程[3,4] YAO Yanbin;LEI Xin;LUO Wanjing;LU Cheng(School of Energy Resources,China University of Geosciences(Beijing),Beijing 100083;Beijing Key Laboratory of Unconventional Natural Gas Geological Evaluation and Development Engineering,Beijing 100083;National Engineering Research Center for Natural Gas Hydrate Exploration and Development,Guangzhou 511458,Guangdong;Oil&Gas Survey,China Geological Survey,Beijing 100083)

机构地区：[1]中国地质大学(北京)能源学院,北京100083 [2]非常规天然气地质评价及开发北京市重点实验室,北京100083 [3]天然气水合物勘查开发国家工程研究中心,广东广州511458 [4]中国地质调查局油气资源调查中心,北京100083

出　　处：《长江大学学报（自然科学版）》2023年第5期21-33,共13页Journal of Yangtze University(Natural Science Edition)

基　　金：国家自然科学基金杰出青年科学基金项目“煤层气储层地质学”(42125205);中国地质调查局项目“天然气水合物产能模拟与调控”(DD20211350)。

摘　　要：天然气水合物的开发利用对于缓解我国能源安全危机、优化能源结构、助力“碳达峰碳中和”目标的实现具有重要意义。我国南海神狐海域水合物资源量巨大,但该区水合物储层为典型的泥质粉砂型细粒沉积,具有储层原始渗透率低、渗透率受扰动变化大的特点,给该类储层水合物开发带来诸多挑战。为了解决泥质粉砂型水合物储层降压开采过程中渗透率变化预测难题,在分析总结南海神狐海域水合物储层样品颗粒、孔隙结构及孔隙流动性等微观特征的基础上,制作了模拟储层条件的人造岩心样品,开展了岩心尺度的水合物分解诱导渗透率动态变化模拟实验,揭示了水合物分解(正)效应和有效应力增高(负)效应对水合物储层气体渗透率变化的影响机理,推导了同时考虑两种效应耦合的渗透率预测模型。研究结果表明,推导的考虑两种效应耦合的渗透率模型比常规仅考虑水合物分解效应的模型更加可靠,且对于泥质粉砂细粒水合物储层具有较好的适用性。将该模型应用于南海神狐海域水合物储层,提出了水合物降压开采过程中的“三段、两压”控制理论:①水合物储层降压开采全生命周期中储层气体表观渗透率呈“降低升高降低”变化过程,“反弹”点发生在“分解压力”附近;②当储层压力高于“分解压力”时,储层渗透率变化主要受有效应力影响,当储层压力低于“分解压力”之后,分解效应的影响大于有效应力效应;③根据“分解压力”和“衰竭压力”两个关键压力点,提出了针对3个阶段不同的水合物降压排采措施。研究成果有望为下步南海神狐海域水合物开采降压策略的制定提供一定的理论依据与方法借鉴。The development and utilization of natural gas hydrates(NGHs)is of great significance to alleviate China’s energy security crisis,optimize the energy structure,and help achieve the target of“peaking CO_(2) emissions and carbon neutrality”.The amount of hydrate resources in the Shenhu area of the South China Sea is huge,but the reservoir of NGHs in this area belongs to the typical fine-grained clayey-silty sediment with low primary reservoir permeability and large permeability change by disturbance,which brings many challenges to the hydrate exploitation of such reservoir.To solve the problem in the prediction of permeability change in the process of depressurization mining of the fine-grained clayey-silty hydrate reservoir,based on the analysis and summary of the microscopic characteristics of hydrate reservoir samples such as particles,pore structure and pore fluidity in the Shenhu sea area of the South China Sea,artificial core samples were made to simulate reservoir conditions.Then,core-scale simulation experiments on dynamic permeability changes induced by hydrate decomposition were carried out.Finally,the influence mechanism of hydrate decomposition(positive)effect and effective stress increase(negative)effect on gas permeability change of the hydrate reservoir was revealed,and the permeability prediction model considering the coupling of two effects was deduced.The results show that the derived permeability model considering the coupling of the two effects is more reliable than the conventional model only considering the effect of hydrate decomposition,and has better applicability to the fine-grained clayey-silty NGHs reservoir.The model was applied to the NGHs reservoir in the Shenhu area of the South China Sea,and the control theory of“three stages and two pressures”in the process of the depressurization exploitation of hydrate was proposed,i.e.,①In the whole life cycle of hydrate reservoir depressurization exploitation,the change of reservoir permeability emerges a“decrease-increase-decreas

关 键 词：天然气水合物 降压开采 南海神狐海域 泥质粉砂沉积物 渗透率与饱和度 有效应力 

分 类 号：TE122.23[石油与天然气工程—油气勘探]