Distribution and Controlling Factors of High Quality Carbonate Reservoir of Yingshan Formation in Northern Slope of Tazhong Area, Tarim Basin
Xiaodong Lan1,2, Xiuxiang Lu1,2, Hongfeng Yu³, Jie Zhou1,2, and Feng Zhu1,2
¹School of Earth Science, China University of Petroleum, Beijing, China
²State Key Laboratory of Petroleum Resources and Prospecting, Beijing, China
³Tarim Oilfield Company, PetroChina, Xinjiang, China
The Ordovician carbonate of Tazhong area is one of key areas for oil/gas prospecting of Tarim basin. Recently, great exploration breakthrough was got in the Yingshan formation of Lower Ordovician. At a great burial depth and high degree of diagenesis, matrix pores in carbonate reservoir beds have nearly disappeared. The tight reservoir beds are controlled by multiple factors with complex oil/gas/water distribution, which seriously affects the regional exploration. By the studies of core, thin slice, seismic and logging, the Yingshan formation is divided into four sections, and high quality carbonate reservoirs are developed in the interstratal karst of the first and second sections of Yingshan formation, faults and associated fractures, dolomitization development area. The reservoirs are influenced by facies, palaeogeomorphology, structure, and so on. Four sedimentary microfacies are developed in Yingshan formation, which are high energy psammogenic beach, low-to-moderate energy psammogenic beach, interbank sea and semi-closure lagoon. The beach facies is benefit for the high quality reservoir. The Yingshan formation is denuded from NW to SE. The reservoir in denudation area of first section is developed in the lower subsection, and dominated by the types of fracture-cave and fracture. However, the reservoir in denudation area of second section is developed in the upper and lower subsections, and dominated by the types of fracture-cave and vug. In whole, the Yingshan reservoir is dominated by the types of fracturecave and vug, and quasi-layer distributed 260m below the unconformity. The dolomization can create vug and pore for reservoir. The dolomite has buried and hydrothermal origins. The dolomite has buried and hydrothermal origins, which control the distribution of layered dolomite and local vertical hydrothermal dolomite, respectively. Tectonic movements, especially the strike slip faults and fissures active in later period, reform the reservoir greatly. Therefore high quality reservoir is based on the heavy-bedded sediment of beach facies, and controlled by the interstratal karst as the key factor of fracture-cave reservoir. With the reformation of faulting and dolomization, the Yingshan formation is a complex reservoir, which is layered and local vertical.
AAPG Search and Discovery Article #90175©2013 AAPG Hedberg Conference, Beijing, China, April 21-24, 2013