Gas Well Decline Analysis Under Constant-Pressure Conditions, Wellbore Storage, Damage, and Non-Darcy Flow Effects

Gas Well Decline Analysis Under Constant-Pressure Conditions, Wellbore Storage, Damage, and Non-Darcy Flow Effects Ibrahim Sami Nashawi; Ibrahim Sami Nashawi Kuwait University Search for other works by this author on: This Site Google Scholar Fuad H. Qasem; Fuad H. Qasem Kuwait University Search for other works by this author on: This Site Google Scholar Ridha Gharbi; Ridha Gharbi Kuwait University Search for other works by this author on: This Site Google Scholar Mohammad I. Mir Mohammad I. Mir Kuwait University Search for other works by this author on: This Site Google Scholar Paper presented at the SPE Gas Technology Symposium, Calgary, Alberta, Canada, April 2002. Paper Number: SPE-75526-MS https://doi.org/10.2118/75526-MS Published: April 30 2002 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Get Permissions Search Site Citation Nashawi, Ibrahim Sami, Qasem, Fuad H., Gharbi, Ridha, and Mohammad I. Mir. "Gas Well Decline Analysis Under Constant-Pressure Conditions, Wellbore Storage, Damage, and Non-Darcy Flow Effects." Paper presented at the SPE Gas Technology Symposium, Calgary, Alberta, Canada, April 2002. doi: https://doi.org/10.2118/75526-MS Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAll ProceedingsSociety of Petroleum Engineers (SPE)SPE Unconventional Resources Conference / Gas Technology Symposium Search Advanced Search AbstractThis paper presents a simple and accurate method to determine all the reservoir parameters for transient constant-pressure drawdown data of gas wells influenced by wellbore storage, formation damage, and high-velocity flow effects. The working equations are written in such a way that allows a graphical analysis of the measured variable rate with time that is very much similar to the analysis of constant-rate production case. No iterative procedure, multi-rate test, nor non-linear regression is necessitated to determine the formation damage and the non-Darcy flow effects. The well test data analysis requires two plots to directly obtain all the parameters of interest. The formation permeability and the non-Darcy flow coefficient are obtained from the first plot, whereas the skin factor is obtained from the second analysis plot.This work systematically illustrates the applicability of the derived equations using several simulated examples. The final working equations are written in various forms, which allows the well test analyst to select the form that is most convenient for his application. The advantages of the proposed method are clearly shown when the analysis procedure and results are compared to other analysis techniques.IntroductionThe vast majority of gas well tests are conducted assuming constant-rate production conditions, even though constant-pressure production have many applications, such as production into constant-pressure separator or pipeline and open flow to atmosphere, furthermore, well tests and field practices have shown that the flow in low-permeability reservoirs (k<1 md) approaches constant-pressure behavior.1As early as 1949, van Everdingen and Hurst2 presented analytical solutions for radial flow of a well producing under constant-pressure conditions. In 1952, Jacob and Lohman3 derived an analytical solution in terms of dimensionless flow rate for a well that produces under constant-pressure conditions. Samaniego and Cinco-Ley4 investigated constant-pressure production in pressure sensitive formations. Ehlig-Economics and Ramey5,6 and Uraiet and Raghavan7,8 presented drawdown and buildup tests for wells producing under constant-pressure conditions.Rate-decline analyses of gas wells producing from low-permeability reservoirs have been also discussed in the literature.9–13 In general, the main feature that makes the interpretation of gas well tests more difficult to analyze than their counterpart of oil wells is the presence of non-Darcy effects due to high-velocity flow around the wellbore.14,15 If not properly recognized, these effects may mask the presence of a fracture in the vicinity of the wellbore. Non-Darcy effects have been commonly treated as an additional rate-dependent skin.Several authors presented different techniques for rate-decline analysis of gas wells under the influence of high-velocity flow effects. These techniques were based on either simulated results11 or analytical methods.12,13,16 Most of the presented papers, however, estimated the non-Darcy flow coefficient using Lee et al.17 correlation. Type-curve matching is also used to analyze rate-decline of gas wells9,18–21 despite of the non-uniqueness problem associated with this technique.The determination of the non-Darcy flow coefficient presents the most challenging task that the well test analysts face in gas well testing. Numerous theoretical models22–24 and empirical17,25–32 correlations are presented in the literature for this purpose. The objective of these correlations is to simplify the job of the reservoir engineer, however, the diversity of the correlations and sometimes contradicting results make the selection of the appropriate one a cumbersome task. A literature survey conducted by Li and Engler33 included most of the available correlations. Keywords: drillstem testing, permeability, flow coefficient, equation, tech, wellbore storage, gas well decline analysis, cartesian plot, mechanical skin factor, coefficient Subjects: Formation Evaluation & Management, Drillstem/well testing This content is only available via PDF. 2002. Society of Petroleum Engineers You can access this article if you purchase or spend a download.

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