Study on Microscopic Pore Structure Classification for EOR of Low Permeability Conglomerate Reservoirs in Mahu Sag

Yong Wang, Xubin Zhao, Chuanyi Tang, Xuyang Zhang, Chunmiao Ma (), Xingyu Yi, Fengqi Tan (), Dandan Zhao, Jie Li and Yuqian Jing
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Yong Wang: Xinjiang Oilfield Company, PetroChina, Karamay 834000, China
Xubin Zhao: Xinjiang Oilfield Company, PetroChina, Karamay 834000, China
Chuanyi Tang: Xinjiang Oilfield Company, PetroChina, Karamay 834000, China
Xuyang Zhang: Xinjiang Oilfield Company, PetroChina, Karamay 834000, China
Chunmiao Ma: Key Laboratory Computational Geodynamics, Chinese Academy of Sciences, Beijing 100049, China
Xingyu Yi: Xinjiang Oilfield Company, PetroChina, Karamay 834000, China
Fengqi Tan: Key Laboratory Computational Geodynamics, Chinese Academy of Sciences, Beijing 100049, China
Dandan Zhao: Xinjiang Oilfield Company, PetroChina, Karamay 834000, China
Jie Li: Xinjiang Oilfield Company, PetroChina, Karamay 834000, China
Yuqian Jing: Key Laboratory Computational Geodynamics, Chinese Academy of Sciences, Beijing 100049, China

Energies, 2023, vol. 16, issue 2, 1-14

Abstract: The microscopic pore structure controls the fluid seepage characteristics, which in turn affect the final recovery of the reservoir. The pore structures of different reservoirs vary greatly; therefore, the scientific classification of microscopic pore structures is the prerequisite for enhancing the overall oil recovery. For the low permeability conglomerate reservoir in Mahu Sag, due to the differences in the sedimentary environment and late diagenesis, various reservoir types have developed in different regions, so it is very difficult to develop the reservoir using an integrated method. To effectively solve the problem of microscopic pore structure classification, the low permeability conglomerate of the Baikouquan Formation in Well Block Ma18, Well Block Ma131, and Well Block Aihu2 are selected as the research objects. The CTS, HPMI, CMI, NMR, and digital cores are used to systematically analyze the reservoir micro pore structure characteristics, identify the differences between different reservoir types, and optimize the corresponding micro pore structure characteristic parameters for reservoir classification. The results show that the pore types of the low permeability conglomerate reservoir in the Baikouquan Formation of the Mahu Sag are mainly intragranular dissolved pores and residual intergranular pores, accounting for 93.54%, microfractures and shrinkage pores that are locally developed, accounting for 5.63%, and other pore types that are less developed, accounting for only 0.83%. On the basis of clear pore types, the conglomerate reservoir of the Baikouquan Formation is divided into four types based on the physical properties and microscopic pore structure parameters. Different reservoir types have good matching relationships with lithologies. Sandy-grain-supported conglomerate, gravelly coarse sandstone, sandy-gravelly matrix-supported conglomerate, and argillaceous-supported conglomerate correspond to type I, II, III, and IV reservoirs, respectively. From type I to type IV, the corresponding microscopic pore structure parameters show regular change characteristics, among which, porosity and permeability gradually decrease, displacement pressure and median pressure increase, maximum pore throat radius, median radius, and average capillary radius decrease, and pore structure becomes worse overall. Apparently, determining the reservoir type, clarifying its fluid migration rule, and formulating a reasonable development plan can substantially enhance the oil recovery rate of low permeability conglomerate reservoirs.

Keywords: Mahu Sag; low permeability conglomerate; EOR; reservoir classification; microscopic pore structure (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2023
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