| Abstract:As a typical example of the whole oil and gas system, Fengcheng Formation in Mahu Depression of Junggar Basin is a potential area for exploration and development of large-scale oil reservoirs in the future. In order to clarify the reservoir densification process and hydrocarbon accumulation model of Fengcheng Formation in Mahu Depression, this paper establishes the second Fengcheng Formation in geological history by using XRD, SEM and other experimental data based on core, cast thin slice and production dynamics. The following understandings have been obtained: 1) Compaction played a leading role in the late Permian, and the devitrification of salt minerals and crystalline dolomites in the second member of Fenghe formed more micro pore space; Early Triassic organic acid dissolution formed reservoir space and created favorable conditions. In the early Jurassic, the dolomitization was intense, and organic acids further dissolved feldspar and carbonate minerals. 2) The reservoirs of the late Permian Shifengcheng Formation were not dense, some lithofacies began to densify in the middle and late early Triassic, and most of the reservoirs became dense from the early Jurassic, with only local sweet spots. 3) In the late Permian, buoyancy and hydrocarbon generation pressurization played a role together. After the early Triassic century, hydrocarbon generation pressurization was gradually taken as the main driving force, and developed into the characteristics of the whole hydrocarbon system. Through the above research, it is expected to provide support for the next oil and gas exploration of Fengcheng Formation in Mahu depression. |
