考虑应力敏感效应下南海低渗水合物储层产能预测建模与分析

There are abundant natural gas hydrates discovered in the South China Sea, which has entered into the stage of field trial. Numerical simulation is a critical means of production prediction. The rationality of models and accuracy of predictions are very important for the selection of target area and scheme design in the test production stage. However, most of the existing models for production prediction fail to take into account the influence of stress field variation on gas and water recovery, but the effect of sediment consolidation on seepage is extremely obvious for the low-permeability hydrate reservoirs. Therefore, it is necessary to establish a prediction model considering stress sensitivity, and then employ it to optimize the depressurization design according to the field data of hydrate reservoirs in the South China Sea. This project will construct a fully coupled production prediction model for hydrate reservoirs with low permeability in this area by utilizing the relationship built from seepage experiment and modifying the existing model and investigate the production performance of different well designs and downhole pressure. After that, the optimized depressurization scheme can be suggested for gas recovery from hydrate reservoirs in the South China Sea. The above research has important theoretical significance and application value for the construction of pilot natural gas hydrate exploration and exploitation region in Shenhu area of the South China Sea and production industrialization. Of course, it is also of great strategic significance for our country to cope with energy shortage and climate change, and safeguard national energy security and social sustainable development.

我国南海赋存有大量的天然气水合物资源，目前已进入现场试采研究阶段。数值模拟作为产能预测研究的一种重要手段，其模型合理性和预测结果准确性对试采靶区选择和方案设计至关重要。现有水合物产能预测模拟常忽略应力场变化对水气流动的影响，然而对于低渗水合物储层来说，地层固结压实效应对渗流的影响非常明显。因而迫切需要针对南海水合物储层自身特性，建立考虑应力敏感效应的产能预测模型并进行分析。据此，本项目将充分利用室内渗流实验结果所建立的应力敏感关系，修改已有产能预测模型，建立针对南海低渗水合物储层的全耦合产能预测模型，分析不同开采井方案和开采压差下的产气产水规律，优选出南海低渗水合物储层降压开采方案，为后续试采提供参考。上述研究对于我国南海神狐海域天然气水合物勘查开采先导试验区建设以及水合物产业化具有重要的理论意义和应用价值，对我国应对能源短缺和气候变化、保障国家能源安全和社会可持续发展具有重要的战略意义。

我国南海赋存有大量的天然气水合物资源，目前已进入现场试采研究阶段。数值模拟作为产能预测研究的一种重要手段，其模型合理性和预测结果准确性对试采靶区选择和方案设计至关重要。现有水合物产能预测模拟常忽略应力场变化对水气流动的影响，然而对于低渗水合物储层来说，地层固结压实效应对渗流的影响非常明显。因而迫切需要针对南海水合物储层自身特性，建立考虑应力敏感效应的产能预测模型并进行分析。据此，本项目构建了考虑渗透率应力敏感效应下的水合物储层渗流模型，厘清了南海低渗水合物储层渗流响应特性，形成了复杂水合物储层开采预测建模和后处理技术，实现了水合物钻采预测快速建模与准确评价。在此基础上，揭示了储层分布特征对水合物开采响应行为的影响规律，提出了水合物储层高效增产技术思路与设想，系统分析了不同开采井身结构设计和开采压差条件下的储层产能，构建了适用于水合物储层的产能方程。在项目执行期间共计发表学术论文15篇，其中SCI/EI检索论文14篇，投稿在审论文3篇，待投稿论文2篇，登记软件著作权3件，开展国内外学术会议并作口头报告交流8人次。与此同时，先后协助培养博士研究生2名，硕士研究生4名。依托该基金产出的科研成果获得2020年湖北省科技进步一等奖1项和2021年度石油工程岩石力学十大科技进展1项。上述研究对于我国南海神狐海域天然气水合物勘查开采先导试验区建设以及水合物产业化具有重要的理论意义和应用价值，对我国应对能源短缺和气候变化、保障国家能源安全和社会可持续发展具有重要的战略意义。