Investigating the variation of water content in shale reservoir is important to understand shale gas enrichment and evaluate shale gas resource potential. Low water saturation is widely spread in Longmaxi marine organic-rich shale. To illustrate the formation mechanism of low water saturation, this paper analyzed water saturation of Longmaxi shale reservoir, restored the history of natural gas carrying water capacity combining homogenization temperature and trapping pressure of fluid inclusion with simulated thermal history, and established a model to explain pore water displaced by natural gas during the thermal evolution. Results show that the gas-rich Longmaxi shale reservoir is characterized by low water saturation with measured values ranging from 9.81% to 48.21% and an average value of 28.22%. TOC in high-mature to over-high-mature Longmaxi organic-rich shale is negatively correlated with water saturation, indicating that well-connected organic pores are not available for water. However, quartz and clay mineral content are positively correlated with water saturation, which suggests that inorganic-matter-hosted pores are the main storage space for water formation. The water carrying capacity of natural gas varies as a function of gas generation and expulsion history, which displaces bound and movable water in organic pores that are part of bound and movable water from inorganic pores. The process can be divided into two phases. The first phase occurred due to the kerogen degradation into gas at Ro of 1.2%–1.6% with a water carrying capacity of natural gas ranging from 5 632.57–7 838.73 g/km³. The second phase occurred during the crude oil cracking into gas at Ro>1.6% with a water carrying capacity of natural gas ranging from 10 620.04 and 19 480.18 g/km³. The water displacement associated with natural gas generation and migration resulted in gas filling organic pores and gas-water coexisting in the brittle-mineral-hosted pores and clay-mineral-hosted pores.

研究页岩储层含水量的变化对于了解页岩气富集和评估页岩气资源潜力具有重要意义。龙马溪海相富有机质页岩普遍存在低含水饱和度。为阐明低含水饱和度的形成机制，本文通过对龙马溪页岩储层含水饱和度的分析，结合均质温度和流体包裹体圈闭压力与模拟热史，还原了天然气携水能力的历史，并建立了解释孔隙的模型。在热演化过程中被天然气置换的水。结果表明，龙马溪富气页岩储层含水饱和度低，实测值为9.81%～48.21%，平均值为28.22%。高成熟至超高成熟龙马溪富有机质页岩的 TOC 与含水饱和度呈负相关，表明连通性良好的有机孔隙不能供水利用。然而，石英和粘土矿物含量与水饱和度呈正相关，这表明无机物质孔隙是水形成的主要存储空间。天然气的载水能力随气体的生成和排出历史而变化，它取代了有机孔隙中的束缚水和可移动水，而有机孔隙中的束缚水和可移动水是无机孔隙中束缚水和可移动水的一部分。该过程可以分为两个阶段。第一阶段发生是由于干酪根在 然而，石英和粘土矿物含量与水饱和度呈正相关，这表明无机物质孔隙是水形成的主要存储空间。天然气的载水能力随气体的生成和排出历史而变化，它取代了有机孔隙中的束缚水和可移动水，而有机孔隙中的束缚水和可移动水是无机孔隙中束缚水和可移动水的一部分。该过程可以分为两个阶段。第一阶段发生是由于干酪根在 然而，石英和粘土矿物含量与水饱和度呈正相关，这表明无机物质孔隙是水形成的主要存储空间。天然气的载水能力随气体的生成和排出历史而变化，它取代了有机孔隙中的束缚水和可移动水，而有机孔隙中的束缚水和可移动水是无机孔隙中束缚水和可移动水的一部分。该过程可以分为两个阶段。第一阶段发生是由于干酪根在 取代无机孔隙中结合和可动水的有机孔中的结合和可动水。该过程可以分为两个阶段。第一阶段发生是由于干酪根在 取代无机孔隙中结合和可动水的有机孔中的结合和可动水。该过程可以分为两个阶段。第一阶段发生是由于干酪根在Ro为 1.2%–1.6%，天然气载水量为 5 632.57–7 838.73 g/km ³。第二阶段发生在原油裂解成气过程中，Ro >1.6%，天然气载水量为10 620.04～19 480.18 g/km ³。与天然气的生成和运移相关的水驱替导致有机孔隙中的气体充填，气水共存于脆性矿物赋存孔隙和粘土矿物赋存孔隙中。