Abstract
Fluid flow in actual oil reservoirs is consistent with material balance, which should be described by the nonlinear governing equation, including the quadratic gradient term (QGT). Nonetheless, the widely-used Blasingame production decline analysis (BPDA) is established based on the conventional governing equation neglecting the QGT, which leads to some errors in the interpretation of production data under some conditions, such as wells producing at a large drawdown pressure. This work extends BPDA to incorporate the effect of the QGT by modifying material balance time and normalized rate functions. The step-by-step procedure for the proposed production decline analysis (PPDA) is presented and compared with that for BPDA. The simulated cases for various production scenarios are used to validate PPDA. A field case is employed to show the applicability of PPDA in practice. Comparisons between the results obtained by BPDA and PPDA are analyzed in detail. It is found that BPDA overestimates the permeability and original oil-in-place, while PPDA works well. Compared with BPDA, PPDA can be employed to obtain more accurate original oil-in-place and reservoir properties, especially when wells produce at a large drawdown pressure.
Highlights
Production decline analysis is considered to be an important reservoir engineering method for reservoir characterization and evaluation in the development of oil reservoirs, where production data is employed to estimate reservoir properties and original oil-in-place [1,2,3,4]
Blasingame production decline analysis (BPDA) has been developed to interpret production data of various wells in different reservoir scenarios, BPDA is established based on the conventional governing equation without the quadratic gradient term (QGT), which is inconsistent with material balance
We extended BPDA to incorporate the impact of the QGT by modifying material balance time and normalized rate functions, and simulated cases for various production scenarios were used to validate proposed production decline analysis (PPDA)
Summary
Production decline analysis is considered to be an important reservoir engineering method for reservoir characterization and evaluation in the development of oil reservoirs, where production data is employed to estimate reservoir properties (e.g., formation permeability) and original oil-in-place [1,2,3,4]. The original version of Arps’ production decline analysis is only applicable to the cases of wells producing at a constant bottomhole pressure during the boundary dominated flow period, and the modified versions were proposed to deal with various production conditions in different reservoir scenarios [17,18]. Blasingame and his co-workers developed production decline analysis for variable-rate/pressure cases based on material balance time, which was known as BPDA [23,24]. BPDA has been developed to interpret production data of various wells in different reservoir scenarios, BPDA is established based on the conventional governing equation without the quadratic gradient term (QGT), which is inconsistent with material balance. Comparisons between BPDA and PPDA were discussed in detail
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