The Diagenesis Study of Tight Sandstone Reservoir of Lower Cretaceous in The Steep Slope Aera of Baiyinchagan Depression, Erlian Basin, China

Ji, Youliang; Zhou, Yong

Baiyinchagan depression is a secondary tectonic unit of Erlian Basin in China, and it is a half rift depression which is developed during the stage of Hercynian orogeny. Fan delta and subwater fan reservoir which is composed of pyroclastic sandstone are developed near the steep slope area of Baiyinchagan depression, and there is a great oil exploration potential in this area. In this paper, varieties of analysis data were used to study the sedimentary characteristics, diagenesis, micro-pore structures and reservoir properties and other basic reservoir features of the target layers. The target layers include Aershaner Formation, Tengeer Formation and the first member of Durimu Formation.

Through the study, it is found that the reservoirs of the target layers are composed of lithic pyroclastic sandstone with lower compositional maturity and middle textural maturity. The major rock types are lithic pyroclastic standstone and lithic feldspathic sandstones. The pore types of Aershaner Formation and Tengeer Formation are secondary pores, the porosity and permeability are relatively lower. The pore type of the first member of Durimu Formation is primary pore, the porosity and permeability are relatively high.

The main diagenesis happened in the studied area are compaction, cementation and dissolution, and the cementation and dissolution have a great influence on the property of the reservoir of the studied area. The diagenetic stage of Aershaner Formation is in the B period of the middle diagenetic stage. The diagenetic stage of Tenggeer Formation is in the A to B period of the middle diagenetic stage. The diagenetic stage of the first member of Durimu Formation is in the B period of the early diagenetic stage. The major diagenetic phase of the studied area is strong compaction, matrix packing, strong cementation, weak compaction, weak cementation and dissolution.

Sedimentary facies, buried depth, structural position and others are the main factors which affect the reservoir property, and the reservoir property controlled the distribution of oil and gas trap. According the models of sedimentary facies and the phase of diagenesis, a diagenentic model are established and the "sweet point" area are predicted.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013