川东南下志留统与Appalachian泥盆系典型常压页岩气藏富集特征对比

Comparison of Enrichment Characteristics of Typical Normally-Pressured Shale Gas Reservoirs in Lower Silurian Shale in Southeastern Sichuan Basin and Devonian Shales in Appalachian Basin

经各国持续攻关,超压页岩气在大多国家实现了商业化开发,但常压页岩气仅美国实现了商业化开发.为了摆脱我国高天然气对外依存度的现状,应尽快实现常压页岩气的商业化开发,亟需对其富集特征展开研究,期望对勘探开发方案的制定提供指导.从川东南下志留统与Appalachian泥盆系典型常压页岩气储层的构造沉积差异演化开始,分析了储层地球化学与页岩气赋存特征差异,明确中美常压页岩气藏富集的差异性.相较于Appalachian泥盆系Marcellus页岩、Ohio页岩的较简单构造改造、富含II-III型干酪根、高含气孔隙度以及气藏远出露区,川东南下志留统五峰-龙马溪组页岩层虽富含高过熟I型干酪根,但经历多期复杂构造运动,底板较破碎、地层倾角较大,页岩气易顺层运移至破碎底板处和露头区逸散,其含气性略低于Marcellus页岩.Ohio页岩虽含气性较低、富集程度不高,但由于其埋藏浅、温压低,更易降压解吸形成工业气流.

After continuous research in various countries,overpressured shale gas has been commercially developed in most countries,but normally-pressured shale gas has only been commercially developed in the United States.In order to overcome the current situation of China’s high external dependence on natural gas,the commercial development of normally-pressured shale gas will play significant role to fulfill the demand in natural gas.It is urgent to study its enrichment characteristics,which may provide guidance for the formulation of development plans.This study starts from the tectonic&sedimentary evolution of typical normallypressured shale gas reservoirs in the Lower Silurian shale of Sichuan Basin and Devonian shales of the Appalachian Basin.Then,the differences in reservoir geochemistry and shale gas occurrence characteristics are analyzed.Finally,the paper conducts the comparion analyses in the enrichment of normally-pressured shale gas reservoirs in China and the United States.Compared to the Appalachian Devonian Marcellus shale and Ohio shale with simple structural deformation,rich type II-III kerogen,high gasbearing porosity and far away from outcrop,the Lower Silurian Wufeng-Longmaxi Formation shale layer in southeastern Sichuan is rich in high-mature type I kerogen,and has undergone multiple stages of complex tectonic movement.This means that underlain formation is more structurally-deformed,the formation dip angle is larger,and the shale gas is easy to migrate to the underlain fractured rock and outcrop area to leak,so its gas content is slightly lower than that of Marcellus shale.But for the Ohio shale,even though which has low gas content and low enrichment,it is easier to reach industrial gas flow by depressurization due to its shallow burial and low temperature and pressure.