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Energies 2018, 11(1), 80; doi:10.3390/en11010080

Well Test Analysis for Fractured and Vuggy Carbonate Reservoirs of Well Drilling in Large Scale Cave

1
College of Petroleum Engineering, Northeast Petroleum University, Daqing 163318, Heilongjiang, China
2
Oil and Gas Engineering Institute of the Jilin Oilfield, Songyuan 138000, Jilin, China
3
Mewbourne School of Petroleum & Geological Engineering, The University of Oklahoma, Norman, OK 73019, USA
*
Author to whom correspondence should be addressed.
Received: 24 October 2017 / Revised: 20 December 2017 / Accepted: 26 December 2017 / Published: 1 January 2018
(This article belongs to the Section Energy Storage and Application)
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Abstract

A well test analysis model for fractured and vuggy carbonate reservoir of wells drilling in large scale cave considering wellbore storage and skin factor is established in this paper. The Laplace transformation and Stehfest numerical inversion are applied to obtain the results of wellbore pressure. Through the sensitivity analysis of different parameters for the well test typical curves, it is found that the change of the well test curves is in accordance with the theoretical analysis. With the increase of skin factor, the hump of well test typical curves is steeper. The storage ratio influences the depth and width of the concave in the pressure derivative curves. The cross flow coefficient mainly affects the position of the concave occurrence in the pressure derivative curves. The dimensionless reservoir radius mainly affects the middle and late stages of the log-log pressure type curves, and the later well test curves will be upturned for sealed boundary. The duration of the early stage of the log-log curves will become longer when drilling in large scale cave. The effective well radius is increased to a certain extent, which is in full agreement with the conclusions in this paper. The size of the caves has the same effect on the well test typical curves as wellbore storage coefficient. Due to acidification, fracturing, and other reasons, the boundary of the cave will collapse. Therefore, considering the wellbore storage coefficient and skin effect is very important during well testing. However, the existing models for well testing of fractured and vuggy carbonate reservoir often ignore the wellbore storage coefficient and skin effect. For fractured and vuggy carbonate reservoirs of well drilling in large scale cave, the existing models are not applicable. Since the previous models are mostly based on the triple-porosity medium and the equivalent continuum. The well test model for well drilling in large scale cave of fracture-cavity carbonate reservoirs with wellbore storage coefficient and skin factor in this work has significant application value for oil field. View Full-Text
Keywords: carbonate; large scale cave; drilling cave; well test; sensitivity analysis carbonate; large scale cave; drilling cave; well test; sensitivity analysis
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Xing, C.; Yin, H.; Liu, K.; Li, X.; Fu, J. Well Test Analysis for Fractured and Vuggy Carbonate Reservoirs of Well Drilling in Large Scale Cave. Energies 2018, 11, 80.

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