页岩气储层主要特征及其对储层改造的影响

Main Characteristics of Shale Gas Reservoir and Its Effect on the Reservoir Reconstruction

页岩气储层是页岩气以吸附和游离状态为主、少量溶解态赋存于页岩中的非常规天然气储层,非均质性强,并且具有低孔隙度超低渗透率的物性特征,页岩气井完井后需要经过储层改造才能获得理想的产能。水力压裂技术是非常规储层中主要的储层改造方法,以此提高页岩气的可采性。在前期研究的基础上,从页岩空间分布、储层非均质性、岩石组成、地质环境、岩石物性特征等方面分析和总结了页岩气储层的主要地质特征,并探讨了这些特征对储层后期改造的影响。页岩气储层有纵向、横向非均质性之分,这些非均质性归因于页岩组成和结构特性。不同沉积环境和构造背景控制着储层的结构和构造,并进一步制约着岩石力学性质、储层敏感性以及天然孔裂隙的发育。岩石组成与结构、天然孔裂隙发育状况和地应力作用是影响储层改造的重要因素。由此,认识储层地质特征及其对后期改造的影响,不仅对丰富页岩气地质勘探理论具有重要的科学意义,而且对提高页岩气产能和开采效率也具有重要的应用价值。

Shale gas is an unconventional gas which has adsorbent and free state with a small amount of dissol- ving. Its reservoir heterogeneity is strong and has physical characteristics of low porosity, ultra-low permeability. Shale gas reservoir need to make reconstruction after gas well completion to get a good yield. Hydraulic fracturing technology which is commonly used in unconventional reservoir to improve shale gas exploitation. Based on the pre- vious studies, characteristics of shale gas reservoirs are discussed and summarized in detail from the rock distribu- tion, reservoir heterogeneity, composition, geological environment, petro physical characteristics and the impact of these characteristics on reservoir reconstruction. Reservoir heterogeneity is very strong no matter in vertical or hori- zontal direction, mainly on the structure and construction of shale gas reservoirs, which owes to organic matter and mineral composition of shales. The structure and composition of shale gas reservoirs are controlled by different tec- tonic background effect, and thereby constrain mechanical properties, reservoir sensitivity of rocks and development of natural fractures. Rock composition, and structure, natural fractures and ground stress play a key role in the shale-gas reservoir transformation. Therefore, this study not only has important scientific significance to broaden theories for shale gas reservoir stimulation, but also has important practical value and production efficiency to im- prove the production of shale gas.