红层油气成藏要素定量评价及成藏概率分析——以东营凹陷博兴地区为例

东营凹陷古近系孔店组一段—沙四段下亚段广泛发育陆相红层沉积。对博兴地区红层油气藏地质特征、分布规律统计发现,烃源岩条件、储集条件、运移条件和保存条件是控制红层油气藏形成和分布的4个成藏要素。考虑影响4个成藏要素控制红层油气成藏概率的有效指标,建立研究区成藏要素的能力指数模型,分别为烃源岩能力指数、储集能力指数、运移能力指数和保存能力指数。研究结果表明,烃源岩能力指数为排烃强度归一化结果,储集能力指数为有效储层厚度归一化结果,运移能力指数为流体势、砂地比和断层运移效率的归一化结果,保存能力指数为排替压力与盖层厚度乘积的归一化结果。利用4个成藏要素的能力指数模型,可以定量评价单一成藏要素的成藏概率,经加权平均赋予不同成藏要素权重系数,进而建立研究区油气成藏概率指数模型。根据该模型预测的有利油气成藏区与博兴地区目前沙四段下亚段红层已发现油气藏进行对比,其结果较为吻合。

Study on quantitative characterization of forming conditions on oil and gas reservoir in red beds and its accumulation probability-taking Boxing area of Dongying depression as an example

Dongying depression of Paleogene period broadly develops continental facies with red bed deposition from the first member of the Kongdian formation to the forth member of the Shahejie formation. According to statistics on the reservoir geological characteristics and distribution rules of Boxing area, it can be found that the four functional elements of the formation and distribution of oil andgas reservoirs are hydrocarbon source rocks (S), reservoir conditions (R), migration condition (M), preservation condition (P). This paper classifies the effective indexes that have influenced on the four functional factors controlling probability of oil and gas distribution, the capability index model of function elements including the capability index of hydrocarbon source rock (Si), the capacity index of reservoir storage (Ri), the capacity index of migration (Mi), and preserving ability index (Pi). The results show that, Si is the normalized result of the expulsion intensity of hydrocarbon (qe); and Ri is the normalized result of effective storage thickness (H); and Mi is the normalized result of the fluid potential, sand ratio, and the migration efficiency of the fault; the Pi is the normalized result of the product of the displacement pressure and the thickness of cover. And, based on that, this paper uses four capability index models of function elements and quantitatively evaluates the control probability function of a single element, eventually, it comprises four functional elements on the temporal and spatial domain, and gives weight coefficient to different function elements by weighted average, and then a probability index model of effective accumulation (SRMP) is set up. Using the calculation results of this model tests, the distribution of reservoir that has been founded, and the coupling results accord well with the current exploration situation.