演变多孔介质天然气水合物动态分解机制及流体驱替特征
Dynamic dissociation mechanism of natural gas hydrate and gas-water displacement characteristics in evolving hydrate-bearing porous media
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- 引用格式:
-
陈明强.演变多孔介质天然气水合物动态分解机制及流体驱替特征[J].天然气与石油,2025,43(4):75-85.doi:10.3969/j.issn.1006-5539.2025.04.011
CHEN Mingqiang.Dynamic dissociation mechanism of natural gas hydrate and gas-water displacement characteristics in evolving hydrate-bearing porous media[J].Natural Gas and Oil,2025,43(4):75-85.doi:10.3969/j.issn.1006-5539.2025.04.011
- DOI:
- 10.3969/j.issn.1006-5539.2025.04.011
- 作者:
- 陈明强1,2,3
CHEN Mingqiang1,2,3
- 作者单位:
- 1. 海洋天然气水合物全国重点实验室, 北京 100028; 2. 中海油研究总院有限责任公司, 北京 100028; 3. 北京怀柔实验室, 北京 101499
1. State Key Laboratory of Offshore Natural Gas Hydrates, Beijing, 100028, China; 2. CNOOC Research Institute Co., Ltd., Beijing, 100028, China; 3. Beijing Huairou Laboratory, Beijing, 101499, China
- 关键词:
- 动态分解机制;微观赋存形态;真实拓扑网络模型;有效孔隙结构;气—水两相驱替特征;保水曲线
Dynamic dissociation mechanism; Hydrate pore habit; Realistic topological network model; Effective pore structure; Gas-water displacement characteristics; Water retention curve
- 摘要:
- 天然气水合物开发过程复杂,相变实时改变流体渗流环境,厘清演变多孔介质天然气水合物动态分解规律及流体驱替特征对实现水合物藏高效产气具有重要意义。首先基于筛选粒径海洋土开展了水合物分解动态CT扫描实验,综合运用物料守恒、化学反应动力学及阈值分割等方式将水合物分解过程数据体有效提取为骨架、水合物、自由水及游离气四相,揭示了分解过程水合物微观赋存形态及有效孔隙结构动态演化规律,利用提取的真实拓扑网络模型探究了水合物分解对气—水两相动态驱替模式及流体赋存特征影响并获取了保水曲线。结果表明,分解过程水合物微观赋存形态由局部胶结型转化为孔隙充填型,水合物分解诱发的有效孔隙结构演变使气—水两相动态驱替模式及同一孔喉流体赋存形态占比产生较大波动,气体侵入最大孔喉所需入口毛管力减小,同一毛管力下气体侵入有效孔喉相对数目增多,保水曲线向含水饱和度减小方向移动。研究成果为天然气水合物开发产气动态分析及预测提供了重要支撑。
Complex phase transition of natural gas hydrate during development continuously alters fluid seepage environment. Understanding the dynamic dissociation mechanism of natural gas hydrate and fluid displacement characteristics is crucial for efficient gas production from hydrate-bearing sediments. In this work, dynamic CT scanning at different stage of hydrate dissociation was first carried out using real marine soil with selected particle sizes. Combined with mass conservation, chemical reaction kinetics, and threshold segmentation methodologies, the obtained 3D CT data were effectively segmented into four phases including solid skeleton, hydrate, free water, and free gas. The dynamic evolution of hydrate pore habit and the effective pore structure were then analyzed during hydrate dissociation. Based on the extracted realistic topological hydrate-bearing networks, pore-scale simulations were carried out to clarify the impact of hydrate dissociation on the dynamic gas-water displacement patterns and fluid occurrence modes within the same pore throat cross-section. The dynamic evolution of the water retention curve was also revealed. Results indicate that hydrate pore habit gradually transitioned from a local cementation or load-bearing type to a pore-filling pattern. Variation in the effective pore structure induced by continuous hydrate dissociation caused significant fluctuations in the proportions of displacement patterns and fluid occurrence modes. The threshold capillary pressure for gas invasion into the largest pore throat decreased. Relative number of the effective pore throats invaded by gas increased at the same capillary pressure. Consequently, the water retention curve shifted towards lower water saturation. This research provides important guideline for the analysis and prediction of dynamic gas production from natural gas hydrate reservoirs.
