Seals or Flow Conduits? How Faults Control Migration and Accumulation in the Shengli Oilfield, China

Lampe, Carolyn¹, Guoqi Song², Liangzi Cong³ (1) Integrated Exploration Systems, 52072 Aachen, Germany (2) SINOPEC (Shengli Oilfield), Dongying, China (3) K.A. Keeping Advanced Oiltech Ltd, Beijing, China

Shengli oilfield, the second largest oil and gas field in China, is one of over fifty faulted Mesozoic-Cenozoic superimposed sub-basins in the Bohai Gulf Basin. Bordered by a dominant northern graben fault, the basin consists of an asymmetrical half-graben, typical of many such structures in eastern China. The basin fill consists mainly of Tertiary sediments that show typical gradation from coarse fluvial graben-shoulder sediments in the north to fine-grained lacustrine sediments in the graben center. Syn-sedimentary movement along the main graben faults resulted in development of many fault blocks, especially along the northern flank of the structure.

Three major source rocks near the Shengli oilfield contribute petroleum to up to seven reservoir horizons. In addition, the source rock and reservoir rock facies are distributed unevenly throughout the system, resulting in complex distributions of possible migration pathways and traps. Some migration pathways consist of stratigraphic conduits, including sandy and conglomeratic facies that occur in the northern graben flank area. However, faults that became active at different times throughout the basin evolution represent the most common conduits for hydrocarbon migration.

Although the sealing or conductive properties of faults for hydrocarbons and the timing of migration are poorly understood, this information is critical to understand the distribution of hydrocarbons within the basin. The Shengli oilfield provides an excellent example of how 3D petroleum systems modeling allows assessment of fault behavior and timing to predict the distribution of hydrocarbons in a petroleum system.