The cross-scale storage and seepage media in carbonate reservoirs are distributed horizontally and vertically, with strong heterogeneity, which leads to complex gas production rules of gas wells. Therefore, it is necessary to explore the main controlling factors of gas well productivity by combining indoor physical experiments and mathematical model calculations on the basis of grasping the law of reservoir seepage. To this end, the gas seepage experiment under the original reservoir condition was first carried out, and then the quasi-threshold pressure measurement experiment, high-speed non-Darcy coefficient measurement experiment and stress sensitivity experiment were carried out in a targeted manner, and finally a trinomial capacity equation considering high-speed non-Darcy effect, low-speed non-Darcy effect and stress sensitivity was established. The numerical calculation results show that: (1) The productivity of gas wells is directly related to the type of reservoir. Fractured-cavity reservoirs have the best quality. Although the seepage capacity of porous reservoirs is weak, they still have certain exploitation value; (2) Stress sensitivity and high-speed non-Darcy effect should be considered in fracture-cavity reservoirs, and the combined effect of the two results in a loss of productivity of 41.82%; (3) The low-velocity non-Darcy effect of the vug-type reservoir is weak. If only stress sensitivity is considered, the resulting productivity loss is 12.53%; (4) Porous reservoirs have weak stress sensitivity. If only the low-velocity non-Darcy effect is considered, the resulting productivity loss is 23.42%. The above research results have important guiding significance for rational production allocation of gas wells in Dengying Formation gas reservoirs of Anyue Gas Field of Sichuan Basin and dynamic prediction of gas reservoir production and development.
Keywords:Dengying Formation
;
Carbonate gas reservoir
;
Horizontal well
;
Stress sensitivity
;
High-speed non-Darcy effect
;
Capacity equation
Jiangtao HU, Shenglai YANG, Beidong WANG, Youjun YAN, Hui DENG, Xiangshang ZHAO. Trinomial capacity equation for horizontal wells in deep carbonate gas reservoirs: Case study of Dengying Formation in Anyue Gas Field, Sichuan Basin. Natural Gas Geoscience[J], 2023, 34(7): 1112-1122 DOI:10.11764/j.issn.1672-1926.2023.02.014
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