辽西凹陷A油田特稠油油藏成因探讨

The Genesis of Super-heavy Oil Reservoirs of A Oilfield in Liaoxi Depression

辽西凹陷A油田在浅层发现大规模特稠油油藏,油藏具有油水倒置和油藏边界垂向上呈不规则弧形的特征。针对该特殊现象,利用流体包裹体、原油分析和盆地模拟等地质资料及手段,对其特稠油藏成因进行了分析。结果表明,稠油的形成主要与东营组的2期成藏和生物降解稠化作用密切相关,第1期东营组储层成藏之后遭受了初次降解作用,原油物性变差,降低了对盖层条件的要求,并在第2个成藏期受破坏,运移至浅层,再次经历快速降解作用,在差保存条件下形成大规模的聚集。

A large scale of heavy oil reservoir was discovered in the shallow layer of A Oilfield in Liaoxi Depression,and the reservoir was characterized by the inversion of oil and water and the irregular arc of the reservoir boundary.In view of these special characters,geological data and methods such as fluid inclusion,crude oil analysis and basin simulation were used in this paper,and the geneses of the super-heavy oil reservoirs were analyzed.The results show that the formation of heavy oil is closely related to the two phases of hydrocarbon accumulation and biodegradation and thickening in Dongying Formation.The initial degradation is induced after the hydrocarbon accumulation at the first stage of the Dongying Formation,and the crude oil property becomes poor,which reduces the requirements for the caprock condition,and it is destroyed and moved to the shallow layer during the second accumulation period,and experiences a rapid degradation again.Under the condition of differential preservation,a large scale aggregation is formed.