鄂西渝东区志留系流体封存箱的演化与天然气成藏

Evolution of Silurian Fluid Compartments and Gas Accumulation in Western Hubei-Eastern Chongqing Area

因鄂西渝东区志留系勘探程度甚低,长期以来志留系一直被视为烃源层或盖层。随着建深1井在志留系钻获高压工业气流,曾经的"思维定式"发生了改变。通过对志留系油气成藏条件及碳、氧、锶稳定同位素追踪流体行为轨迹的分析认为,该区志留系具有自源供烃的特点以及流体相对封闭的独特性,这是形成志留系下统龙马溪组、小河坝组以及志留系中统韩家店组自生自储自盖式高压流体封存箱的主要因素。而志留系封存箱在早燕山期以前的构筑、早燕山中—晚期的改造、晚燕山—喜马拉雅期的定型与发展,控制了志留系天然气的成藏过程。

The Silurian strata distributed in the Western Hubei-Eastern Chongqing area were counted once as source rock or cap rock for a long time due to low mature prospecting but the past concept has changed with discovering high-pressured commercial gas flow in Well JS-1 in this area.By analysis of the hydrocarbon accumulation and the fluid behavior tracing from isotope δ13C,δ18O and 87Sr/86Sr,it is shown that the Silurian strata are characterized by self-source hydrocarbon and self-reserving conditions with relatively independent fluid sealing,which is the dominant causation to bring on several abnormally high-pressured fluid compartments from the Lower Silurian Longmaxi and Xiaoheba Formations to the Middle Silurian Hanjiadian Formation.In the whole evolution process,the Silurian hydrocarbon accumulation and preservation have been well under control of the Silurian compartments which were formed before Early Yanshanian,reformed during the middle to late phases of Early Yanshanian and shaped during Late Yanshan-Himalayan periods.