Pressure transient analysis of unsteady-state inter-porosity flows for slanted wells in fractured-vuggy carbonate reservoirs

Articles in Press

Document Type : Research Article

Authors

1 National Key Laboratory of Oil & Gas Reservoir Geology and Exploitation,Southwest Petroleum University, Chengdu ,China

2 Tarim Oilfield Company, PetroChina, Korla, Xinjiang , China;

3 Liquor Making Microbial Application & Detection Technology of Luzhou Key Laboratory, Luzhou Vocational & Technical College, Luzhou, CN 646000 School of Petroleum Engineering, Chongqing University of Science and Technology, Chongqing,, China

4 Xi'an Sanwei Technology Development Co., LTD, Xi’an,, China

5 National Key Laboratory of Oil & Gas Reservoir Geology and Exploitation,Southwest Petroleum University, Chengdu,China

10.24200/sci.2026.67920.10884

Abstract

To address the significant challenges posed by multiscale heterogeneity in fractured-vuggy carbonate reservoirs, we have developed a comprehensive triple-porosity pressure transient model specifically tailored for slanted wells. A central innovation of this work is the rigorous incorporation of a unified unsteady-state interporosity flow mechanism. This approach accurately describes the dynamic fluid transfer from both spherical matrix blocks and distinct vug systems into the interconnected natural fracture network, thereby avoiding the limitations of simplified pseudo-steady state assumptions. The model also integrates essential near-wellbore effects such as wellbore storage and skin factor.Leveraging source function theory and the principle of superposition, a new semi-analytical solution was derived in the Laplace domain, with the real-time pressure response obtained via the Stehfest numerical inversion algorithm. Based on this solution, characteristic type curves were generated, revealing a key diagnostic feature: two successive troughs on the pressure derivative plot. These troughs represent the sequential fluid supply, first from the more permeable vugs and subsequently from the low-permeability matrix. Extensive sensitivity analyses systematically quantified the influence of well geometry and critical reservoir parameters on pressure behavior. Finally, a field example from a carbonate reservoir validated the model's practical applicability, demonstrating excellent agreement with actual test data. Consequently, this work offers a more robust tool for well test interpretation in these highly complex formations.

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Scientia Iranica

Articles in Press, Accepted Manuscript
Available Online from 23 June 2026

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History

  • Receive Date: 28 September 2025
  • Revise Date: 31 January 2026
  • Accept Date: 20 May 2026

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