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Evaluation of skin factor from single-rate gas well test

By Fahad M. Al Mutairi

Abstract

Skin factor is generally used as an indicator for well flow efficiency and the criterion for performing stimulation treatment to improve well productivity. This skin factor is a composite factor and should be divided into its different components in order to evaluate near-wellbore damage. Therefore, the total skin factor obtained from a gas well pressure transient test has two primary components, rate-independent and rate-dependent skins. Both of these skin factors can be determined directly from the interpretation of pressure transient well tests if several transient tests are performed at different rates. However, the multi-rate tests are time consuming and expensive. It is advantageous to estimate the rate-independent skin factor from a single rate test.;In order to obtain a reliable value for the rate-independent skin from a single-rate test, the rate dependent skin must be evaluated independently. The rate-dependent skin depends on the coefficient of inertial resistance, beta and other parameters. A number of correlations relating beta to permeability are available in the literature. These published correlations are derived from limited set of laboratory measurements on various porous media and do not provide consistent results. Alternatively, beta can be determined from the results of the multi-rate well tests using recorded field data.;The main objective of this study is to generate a dependable and simple technique for estimating the true skin factor from the single rate well tests, such as build-up or fall-off tests, on gas wells. More specifically, the objective is to develop a correlation for beta from field data. Since, the correlation of turbulence factor, beta and permeability, k cannot be applied universally to all reservoirs, so the reservoir-specific correlations will be further developed.;The well tests from several wells in the same reservoir were available and several field-specific correlations for beta were developed. The comparison of skin factor determined from these correlations against the skin factors determined from the well test data indicated that reservoir-specific correlations for beta provide accurate and consistent results

Topics: Petroleum engineering
Publisher: The Research Repository @ WVU
Year: 2008
OAI identifier: oai:researchrepository.wvu.edu:etd-2972
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