Characteristics and Influencing Factors of Natural Gas Gravity Drainage in Sanjianfang Formation Reservoir of Pubei Oilfield

doi:10.7657/XJPG20230310

Abstract

Abstract:

To explore the feasibility of natural gas gravity drainage in the Pubei oilfield of the Turpan-Hami basin, the oil displacement characteristics under different operation parameters were clarified. By way of high-pressure physical property analysis, slim tube test, CT scanning imaging, and full-diameter core displacement experiments, the variations of the high-pressure physical properties of the fluids in the Middle Jurassic Sanjianfang formation reservoir before and after the flooding in the Pubei oilfield were analyzed, the minimum miscible pressure of the gas in the Shanshan-Urumqi Gas Pipeline and the West-East Gas Pipeline under current reservoir conditions was calculated, the fluid distribution characteristics and the changes in oil saturation along the core under different displacement methods were compared, and the influences of injection rate, injection pressure, and rock dip angle on natural gas gravity drainage were clarified. The results show that after flooding there are increases in both crude oil density and saturation pressure, an unconspicuous change in viscosity, and significantly decrease contents of C₂-C₆ contents in the crude oil. The minimum miscibility pressures of the gas in the Shanshan-Urumqi Gas Pipeline and the West-East Gas Pipeline with oil are 48.2 MPa and 49.5 MPa, respectively, both higher than the minimum miscibility pressure of the original oil and gas. Compared with the performance after water flooding, the natural gas gravity drainage reveals very different oil saturations along the core: the oil saturation at the high position of the core is significantly lower than that at the low position, indicating that the natural gas gravity drainage is more effective in displacing the crude oil at the high position. Low injection rate, high displacement pressure, and large dip angle are all beneficial to improving the oil recovery of natural gas gravity drainage.

Key words: Turpan-Hami basin, Pubei oilfield, Middle Jurassic, Sanjianfang formation, natural gas gravity drainage, gravity differentiation, recovery factor, influencing factor

CLC Number:

TE357

XIAO Zhipeng, QI Huan, ZHANG Yizhen, LI Yiqiang, YAO Shuaiqi, LIU Tong. Characteristics and Influencing Factors of Natural Gas Gravity Drainage in Sanjianfang Formation Reservoir of Pubei Oilfield[J]. Xinjiang Petroleum Geology, 2023, 44(3): 334-340.

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