Semi-Analytical Model and Flow Characteristics of Asymmetrically Fractured Off-Center Vertical Wells in Tight Gas Reservoirs

doi:10.7657/XJPG20220407

Abstract

Abstract:

To understand the flow regime of asymmetrically fractured off-center vertical wells in tight gas reservoirs,a mathematical model for asymmetrically fractured off-center vertical wells was established according to the mass conservation equation. The bottom-hole pseudo pressure of off-center vertical well in Laplace space was obtained by using Laplace transform and numerical discretization. The time-space distribution of pressure and production were determined by using the Stehfest numerical inversion method,and the impacts of fracture angle,dimensionless fracture conductivity and eccentric distance on bottom-hole pseudo pressure and production were discussed. With the help of Saphir well test interpretation software,the numerical model of gas well was built and the numerical calculation for discretization was performed. The calculated results were compared with the semi-analytical solution to verify the mathematical model. Furthermore,according to the variation characteristics of the dimensionless bottom-hole pseudo pressure,the fluid flow in asymmetrically fractured off-center vertical wells was divided into six stages: bilinear flow stage in reservoir and fracture,linear flow stage in reservoir,elliptical flow stage in fracture,plane radial flow stage,near-fracture boundary-dominated flow stage,and circular closed boundary-dominated flow stage.

Key words: tight gas reservoir, hydraulic fractured well, off-center vertical well, asymmetric fracture, asymmetry factor, bottom-hole pseudo pressure, flow characteristic

CLC Number:

TE312

WANG Yufeng, JI Anzhao, ZHANG Guangsheng, CHEN Zhanjun. Semi-Analytical Model and Flow Characteristics of Asymmetrically Fractured Off-Center Vertical Wells in Tight Gas Reservoirs[J]. Xinjiang Petroleum Geology, 2022, 43(4): 425-432.

Figures/Tables 5

References 33

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