Peigui Yin¹, R.C. Surdam¹, Yao Yimin²

(1) University of Wyoming, Laramie, WY
(2) Shengli Oil Company, Dongying, Shandong, China

ABSTRACT: Petroleum system of the buried-hill reservoirs in the Bohai Basin, China

Highly productive buried-hill carbonate reservoirs have been discovered throughout the Bohai region. The formation of a rich buried-hill reservoir is contingent upon the presence of four crucial elements: (1) mature source rocks, (2) permeable reservoir rocks, (3) a fault that provides a conduit between the reservoir rocks and source rocks, and (4) effective vertical and lateral seals.

The best source rocks adjacent to the Yihezhuang buried-hill reservoir zone are organic-rich shales and oil shales in the First, Third, and Fourth members of the Shahejia Formation in the Sikou Trough, Zhanhua Depression. Velocity modeling indicates that the Tertiary section in the Sikou Trough is hydrocarbon saturated. The oil present in the buried-hill reservoirs in the eastern Yihezhuang zone is derived from these Tertiary source rocks.

Paleozoic Cambrian, Ordovician, Carboniferous, and Permian reservoir rocks and Mesozoic reservoir rocks are in direct contact with mature Tertiary source rocks throughout the northeastern section of the Yinan Fault. Due to a long period of erosion and abundant fractures and faults, all the pre-Tertiary rocks, especially the Ordovician carbonate rocks, are capable of serving as reservoir rocks in the Yihezhuang area.

Digital analysis has revealed a detailed picture of porosity distribution in these carbonate rocks. Micropores can be identified using back-scattered electron images. The pore framework in the carbonate reservoir rocks has been qualitatively and quantitatively evaluated. The Upper Paleozoic and Mesozoic sequences vertically seal the Ordovician carbonate reservoirs in this area and impermeable Tertiary shales block them laterally.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado