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.
Highlights
Most of the word’s giant fields produce from fractured and vuggy carbonate reservoirs that have characteristics of complex pore system, large scale reservoir medium span, the variety of fracture-cavity connected mode, the coexistence of multiple forms of fluid flow [1,2,3,4,5,6], mainly because carbonate rocks are sensitive to post-depositional diagenesis, including dissolution, dolomitization, and fracturing processes
This model can be used to describe the characteristics of 3 offractured and vuggy carbonate reservoirs more truly and the well test analysis results have proper geological the well test curves plotted by the established well test model of fractured and vuggy significance.AtInpresent, this work, we introduce a well test analysis model that is more general and rigorous carbonate reservoirs do not consider wellbore storage and skin effect, and it will be difficult to obtain than previous models
(4) The influence of cross flow coefficient on well test typical curves well drills into the large scale cave, it will make the storage stage of the wellbore become longer in the early stage
Summary
Most of the word’s giant fields produce from fractured and vuggy carbonate reservoirs that have characteristics of complex pore system, large scale reservoir medium span, the variety of fracture-cavity connected mode, the coexistence of multiple forms of fluid flow [1,2,3,4,5,6], mainly because carbonate rocks are sensitive to post-depositional diagenesis, including dissolution, dolomitization, and fracturing processes. This model can be used to describe the characteristics of 3 offractured and vuggy carbonate reservoirs more truly and the well test analysis results have proper geological the well test curves plotted by the established well test model of fractured and vuggy significance.AtInpresent, this work, we introduce a well test analysis model that is more general and rigorous carbonate reservoirs do not consider wellbore storage and skin effect, and it will be difficult to obtain than previous models. We provide parameter for straight-line fracturedflow and regime vuggy carbonate reservoirs considering wellbore storage and skinsolutions effect is established that are with applicable tolarge eachscale flowcave This A model can be used to describe the characteristics fracturedcontrols and vuggysequences carbonate reservoirs more trulyFinally, and the well analysis results haveapplication proper geological on flow-regime and behaviors. We demonstrate actual application of our new model to prevent misinterpretation of flow regimes, and misapplication of local solutions, by
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