海洋天然气水合物成藏系统研究进展及发展方向

Research progress and development direction of reservoir-forming system of marine gas hydrates

天然气水合物成藏系统的研究对于认识具有强非均质性的天然气水合物的资源分布、预测其甜点、提高其勘探成效具有重要的意义。通过综合分析天然气水合物在成藏条件、成藏要素和成藏模式等方面的研究认识和勘探成果,综述了天然气水合物成藏系统在气源、稳定带特征及影响因素、储层类型与特征、运移通道类型和成藏模式等方面的研究新进展。天然气水合物的气源可分为生物气、深部热解气和混合气3种类型;水合物的储层类型包括软泥、粉砂质泥和粉砂等多种类型;在粒度较粗的储层中,水合物的含气饱和度往往相对较高;断层、裂隙、底辟构造、气烟囱和高渗透性地层等是天然气水合物的有效运移通道。前人依据气源及其与水合物稳定带的配置关系、水合物的生成速度与分解速度的消长关系、水合物形成的主控因素、运移通道的类型等建立了多种水合物成藏模式,但对于成藏过程中各成藏要素的时空演化及耦合关系、成藏效率的定量评价等研究仍不足,有必要将天然气从气源灶运移至稳定带的动力学过程与稳定带内天然气的运移、聚集、分解和散失的动力学过程有机结合起来开展研究。采用成藏动力学定量研究的思路和方法,应用大数据和人工智能等新技术来定量表征天然气水合物的成藏要素及其时空演化过程,利用数值模拟方法定量研究在气源灶、运移通道、稳定带和储层耦合条件下的天然气水合物的运移、聚集、分解、散失过程是未来天然气水合物成藏系统研究的发展方向。

The research of the reservoir-forming system of gas hydrates is essential for understanding the resource distribution of gas hydrates with strong heterogeneity, predicting their sweet spots, and improving the exploration efficiency. Through comprehensively analyzing the understandings and exploration results of gas hydrates in terms of accumulation conditions, accumulation factors, and accumulation models, this paper summarizes the new progress in research of gas source, characteristics and influencing factors of stabilization zone, reservoir types and characteristics, types of migration pathways, and accumulation models in the reservoir-forming system of gas hydrates. The gas sources of gas hydrates can be divided into three types: biogenic gas, deep thermal cracking gas and mixed gas. The reservoir types of hydrates include ooze, silty mud, and silt. In coarser reservoirs, the gas saturation of hydrates is often relatively high. Faults, fractures, diapir structures, gas chimneys, and high-permeability formations are effective migration pathways for gas hydrates. Predecessors established a variety of accumulation models of gas hydrates based on the gas source and its configuration relationship with the hydrate stabilization zone, the relationship between the formation rate and decomposition rate of hydrates, the main controlling factors of hydrate formation, the types of migration pathways and the quantitative evaluation of accumulation efficiency. However, there are still insufficient studies on the temporal and spatial evolution and coupling relationship of various accumulation factors during the accumulation process, and it is necessary to conduct research by integrating the dynamic process of gas migration from the hydrocarbon source kitchen to the stabilization zone and that of the migration, formation, accumulation and dissipation of gas in the stabilization zone. This paper adopts the ideas and methods of quantitative research in accumulation dynamics, applies big data, artificial intelligence and other new technologies to quantitatively characterize the accumulation elements of gas hydrates and the relevant temporal and spatial evolution process. In the future, the research of gas hydrate reservoir accumulation system will focus on using numerical simulation methods to quantitatively study the migration, accumulation, decomposition, and dissipation processes of gas hydrates under the coupling conditions of gas source kitchen, migration pathways, stabilization zone and reservoirs.