Fault control on hydrocarbon migration and accumulation in the Tertiary Dongying depression, Bohai Basin, China

Abstract

Shengli oil field, the second largest oil and gas field in China, is located in the Tertiary Dongying graben system in the southern Bohai Basin. Three petroleum systems, one for each mapped source rock, and as many as seven reservoir rocks are documented in the Dongying graben system, representing a complex migration and accumulation pattern. In addition, both the source and the reservoir facies are distributed unevenly throughout the system, requiring a complex distribution of possible migration pathways. Stratigraphic conduits, that is, sandy and conglomeratic facies, are mostly present in the northern graben flank area, where coarse sediments provide possible migration pathways. Over most of the basin, however, faults—active at different times throughout basin evolution—add important additional conduits for petroleum migration, as well as acting locally as seals, depending on their surrounding lithology and their respective sealing or leaking properties through time. This article aims to show that the Shengli oil field provides an excellent example of how three-dimensional petroleum systems modeling allows the assessment of fault behavior and timing to predict the distribution of hydrocarbons in a system.