川东石炭系气藏中固体沥青形成机理探讨

APPROACH TO SOLID MIGRABITUMEN MECHANISM OF CARBONIFEROUS GAS RESERVOIR IN THE EAST OF SICHUAN BASIN

李艳霞 钟宁宁

Li Yanxia Zhong Ningning

西安石油大学, 油气资源学院, 西安, 710065 2. 中国石油大学, 资源与信息学院, 北京, 102249

School of Petroleum Resources, Petroleum University of Xi'an, Xi'an, Shanxi 710065, China 2. Earth Science and Geoinformatics School, China Petroleum University, Beijing 102249, China

针对四川盆地东部石炭系气藏储层中发现的大量固体碳质沥青,通过对其保存产状和碳同位素的分析,表明固体碳质沥青主要充填在碳酸盐岩储层的溶孔(粒间溶孔、粒内溶孔及晶间溶孔)、裂缝及溶洞系统中。固体沥青碳同位素值主要分布在-28.83‰~-23.99‰之间,与气藏中储层沥青抽提物中饱和烃、芳香烃、非烃及沥青质和志留系干酪根碳同位素值相比,其值最重;而甲烷碳同位素值为-37.7‰~-29.2‰,值最轻。固体碳质沥青和甲烷的碳同位素值居于两端,其差值为碳同位素热动力分馏的结果。固体碳质沥青形成机理是原油中芳香烃类富含芳香核的高分子物质缩聚为高碳固体物质的结果。

The formation mechanism of a great deal solid migrabitumens of Carboniferous gas reservoir in the east of Sichuan Basin is discussed.There are high content methane and solid bitumen in the gas reservoir.Solid bitumens mainly distribute system of dissolution pore(intergrain pore,insidegrain pore and intercrystalline pore),fracture(fissure) and dissolution cavity in carbonate reservoir.Compared with other composition in gas reservoir and source rock,such as δ13Csaturated,δ13Caromatic,δ13CNOS,δ13Casphaltenes and δ13Ckerogen,the value of δ13Cbitumen is the heaviest and mainly range from -28.83‰ to -23.99‰.But δ13C value of methane is the lightest and about -37.7‰ to -29.2‰.The difference is result of carbon isotope thermal dynamical frationaction.With increasing depth and rising temperation,there is a tendency for crude oils in reservoirs to become specifically low lighter molecular hydrocarbon and high molecular weight constituent.The ultimate stable end products are low molecular methane and insoluble carbon-rich residue of very high molecular weight.Finally crude oils in reservoirs crack into gas and solid bitumen.The formation mechanism of solid migrabitumen is a result of high molecular with aromatic cycles condensation insoluble carbon-rich residue.

https://doi.org/10.11781/sysydz200704402