29 D22. Sediments, Carbonates

Monday, 26 October 2020
5:30 PM - 8:00 PM
Meeting Rooms

CHARACTERISTICS AND MAIN CONTROLLING FACTORS OF MIDDLE PERMIAN QIXIA FORMATION RESERVOIRS IN SHUANGYUSHI AREA, NW SICHUAN BASIN

Paper number: 29-12
Program: Technical Sessions
Time: 7:40 PM – 7:50 PM

Authors

Abstract

With the further deepening of exploration degree of the Middle Permian Qixia Formation gas reservoirs in Sichuan Basin， China, the high-yield industrial gas flow has been obtained from the Qixia strata of the Shuangyushi structure in northwestern Sichuan Basin. Based on field outcrop, core and well logging data, combined thin section analysis, cathodoluminescence, SEM, mercury intrusion, CT scanning, X-ray diffraction, elemental geochemistry, carbon and oxygen isotope research, this paper analyzes the development characteristics and main controlling factors of dolomite reservoirs in this area. The results show that the thickness of the reservoir is between 10～40m. The reservoirs which develop in the shoal of platform margin facies are mainly crystalline dolomites, followed by a small number of grain dolomites; The reservoir spaces are dominated by dissolution pores (vugs), intercrystalline dissolution pores, intercrystalline pores, followed by a small number of cracks; The physical properties of the reservoirs are characterized by low porosity and low permeability and the reservoir types are mainly fracture-pore (vug) type.

The development and distribution of reservoirs are controlled by sedimentary facies, sedimentary paleogeomorphology, diagenesis, and late tectonic fracture. Sedimentation provides the material basis for reservoir development and sedimentary highlands of paleogeomorphology control the distribution of high-energy shoal area. The high-quality reservoirs are developed in the high-energy shoal of platform margin facies; Penecontemporaneous atmospheric water eluviation not only forms a large number of secondary dissolution pores(vugs) but also provides migration pathway for the fluid of dolomitization; The matrix dolomite in the reservoir has high Fe, Mn content, low Sr content, δEu and δCe are less than 1, and δ13C average 3.15‰, δ18O averages -6.69 ‰, which is similar to the value of the limestone deposited in coeval seawater, confirmed that the matrix dolomite is formed in shallow burial period. The early pores(vugs) are maximally inherited and preserved during the stage of the shallow burial dolomitization; The cracks and dissolution caused by the late tectonic fracture further connect the pores(vugs) system.

Geological Society of America Abstracts with Programs. Vol. 52, No. 6

doi: 10.1130/abs/2020AM-356849

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