渤中坳陷大型油气系统输导体系及其对油气成藏控制

渤中坳陷东营组沉积期以来快速沉降和强烈断裂活动的地质背景导致其呈现出不同于渤海湾盆地其他地区的油气成藏特征.凹陷周缘凸起带成为油气聚集的主要场所, 输导体系的分布与演化控制了油气运移和成藏.在阐明渤中坳陷大型油气系统烃源岩和油气分布规律的基础上, 综合利用多种资料分析了各类潜在输导通道的发育特征及其空间配置, 识别出断裂主导型、砂体主导型和不整合主导型3类控藏输导体系.凸起边缘继承性的长期断层充当了垂向流体释放和油气运移的主输导通道, 控制了凸起带上新近系储集层中的油气聚集.特别是在构造活跃期, 开启的长期断层成为油气快速垂向运移的首选通道.古近系沙河街组和东营组的连通性砂体与活跃烃源岩直接接触, 不仅是早期油气运移和聚集的主要场所, 也是晚期油气运移和聚集的始发站.因此, 它们不仅控制了古近系圈闭的油气聚集, 同时在很大程度上直接控制了凸起带新近系圈闭的油气供给.不整合T₈是中生代末区域构造变革的产物, 其渗透性因风化作用而得以提高, 充当了深部侧向油气运移的输导通道, 控制了潜山储集层中的油气成藏.3类输导体系对油气成藏的时间、部位、速率和规模等都具有不同程度的影响, 但断裂主导型输导体系的控制作用最为显著. 

Pathway System of Large-Scale Petroleum System and Its Controls on Hydrocarbon Accumulation in the Bozhong Sub-Basin, Bohai Bay Basin

The geological evolution of the Bozhong sub-basin, characterized by rapid subsidence and strong fault activities since the initiation of the Dongying Formation, exerts important effect on the characteristics of hydrocarbon accumulation in this area, which is distinguished from those in other areas in the Bohai Bay Basin. Uplifts around depressions serve as predominant sites for hydrocarbon accumulation, and the distribution and evolution of pathway systems have obviously been controlling hydrocarbon migration and accumulation. Based on clarification of the distribution of hydrocarbon source rocks and petroleum resources in the large-scale Bozhong petroleum system, growing characteristics of all kinds of potential pathways and their spatial relevance are analyzed by means of multiple data, and then three pathway system types controlling hydrocarbon migration and accumulation: fault-dominant, carrier bed-dominant and unconformity-dominant types are identified. Long-term growth faults adjoining uplifts act as the predominant pathways for vertical fluid release and hydrocarbon migration, and control hydrocarbon accumulation in the Neogene reservoirs on uplifts. Especially in the active stage of tectonic movement, the open long-term growth faults must be preferential pathways for the rapid vertical hydrocarbon migration. The interconnected sandbodies in the Paleogene Shahejie and Dongying Formations, directly contacting with active hydrocarbon source rocks, serve as the primary sites and starting stations for the early and late hydrocarbon migration and accumulation, respectively. Therefore, they not only control hydrocarbon accumulation in the Paleogene traps, but also directly impact hydrocarbon supply to the Neogene trap on uplifts to some extent. Unconformity T₈, resulted from regionally tectonic transformation in last Mesozoic, serve as pathway for deep lateral hydrocarbon migration and control hydrocarbon accumulation in the buried hill type reservoirs due to its improved permeability attributed to long-term weathering process. Three types of pathway systems all impact even control the times, locations, velocities and scales of hydrocarbon accumulation in various degrees. However, the fault-dominant type pathway system shows the most outstanding effect among them.