Estimation of Effective Permeabilities for Reservoirs Initially Above Bubblepoint Pressure

Estimation of Effective Permeabilities for Reservoirs Initially Above Bubblepoint Pressure D.G. Hatzignatiou D.G. Hatzignatiou U. of Alaska Fairbanks Search for other works by this author on: This Site Google Scholar Paper presented at the SPE Rocky Mountain Regional Meeting, Casper, Wyoming, May 1992. Paper Number: SPE-24373-MS https://doi.org/10.2118/24373-MS Published: May 18 1992 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Get Permissions Search Site Citation Hatzignatiou, D.G. "Estimation of Effective Permeabilities for Reservoirs Initially Above Bubblepoint Pressure." Paper presented at the SPE Rocky Mountain Regional Meeting, Casper, Wyoming, May 1992. doi: https://doi.org/10.2118/24373-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 Rocky Mountain Petroleum Technology Conference / Low Permeability Reservoirs Symposium Search Advanced Search SPE MemberAbstractThis work investigates the effects of initial reservoir pressure on the computation of effective permeabilities for homogeneous and heterogeneous solution-gas-drive reservoirs which are initially above the bubble-point pressure. The heterogeneous system considered is that of a two-zone composite reservoir with different absolute permeability and/or relative permeability curves in the two regions. It is shown that the initial effective oil permeability may be estimated from drawdown and buildup pressure data. It is also shown that one can obtain accurate estimates of computed effective permeabilities as pointwise functions of wellbore pressure from drawdown data during the time period that the wellbore pressure is less than the initial bubble-point pressure. From the estimates of effective permeabilities obtained, it is shown that for the case of homogeneous solution-gas-drive systems one can construct approximate effective (or relative) permeability curves by nonlinear regression analysis techniques. For the case of heterogeneous solution-gas-drive reservoirs it is shown that if the initial reservoir pressure is above the reservoir bubble-point pressure then the effective oil permeability of the inner or the outer zone might be. obtained from the analysis of drawdown and/or buildup pressure data.IntroductionIn the last few years, the estimation of effective (or relative) permeability curves from well-test pressure data has been the subject of several studies. Refs. 1–4 have presented methods for estimating effective permeability as a pointwise function of the wellbore pressure using either drawdown pressure data obtained from multi-rate tests or drawdown pressure data obtained from single-rate, constant oil rate production tests. In addition, Refs. 2 and 4 presented computational methods of estimating effective permeability values as a pointwise function of shut-in wellbore pressure from pressure buildup data. Refs. 5–7 extended the ideas of Refs. 2–4 to examine the influence of wellbore storage on the analysis of pressure data from a solution-gas-drive system and the computation of effective permeability values as a function of pressure. Refs. 5 and 8 presented new methods for estimating effective or relative permeability curves, based on Corey's and Standing's correlations, and the application of nonlinear regression analysis techniques. The results of Refs. 1–8 assumed that the initial reservoir pressure was equal to the initial bubble-point pressure. Al-Khalifah et al. showed that one can use pressure drawdown data obtained from a multirate test to obtain estimates of effective (or relative) permeability values for heterogeneous systems. Ref. 1 concluded that the computed effective or relative permeability values obtained from well-test pressure data reflect the outer zone effective or relative permeability curves. Hatzignatiou and Reynolds extended the results of Ref. 1 and concluded that the effective permeabilities estimated from pressure drawdown or buildup data reflect, at early times, the inner zone effective permeability data and, at later times, the outer zone effective permeability data for the oil phase. Ref. 11, based on theoretical and computational arguments, illustrated that the effective gas permeability values computed from pressure data will not reflect the outer zone effective gas permeability data unless the krg/kro ratio is identical in both the inner and outer zones. Refs. 1–7 have provided methods for approximating the oil and gas effective permeability versus wellbore pressure relationship using the pressure drawdown and buildup data. The results of Refs. 1–5 show that once wellbore storage effects become negligible we can obtain good estimates of kkro and kkrg from pressure drawdown data by applying the following equations:(1)and(2)Eq. 1 assumes that qo is constant and equal to the sandface flow rate.P. 537^ Keywords: simulator, value computed, effective permeability, initial bubble-point pressure, drillstem/well testing, drawdown data, drawdown, artificial intelligence, machine learning, accurate estimate Subjects: Formation Evaluation & Management, Drillstem/well testing This content is only available via PDF. 1992. Society of Petroleum Engineers You can access this article if you purchase or spend a download.

Topic: Reservoir Engineering and Simulation Methods
Subfield: Ocean Engineering
Field: Engineering
Domain: Physical Sciences