Abstract
A procedure of well test analysis using a reservoir simulation model coupled with a history matching program has been developed, The history matching program used in this study is called "Adaptive History Matching (AHM) System" which was developed by Scientific-Software Intercomp (SSI) with the participation of Texaco and two other major oil companies. AHM was designed to help the engineer deal with the problems of history matching reservoir performance data with a reservoir simulator. Pressure data measured in well test is directly history matched with the current method without converting to dimensionless terms or taking the logarithm of the data.
The history matching system used in the current procedure is based on Bayesian inference. Bayes’ theorem provides a process of learning from experience and shows how knowledge about the state of nature can continually be modified as new data becomes available. Four cases of well test analysis are presented in this paper. They include a single well test, an interference well test, a multi-layered reservoir case, and a horizontal well test. In each case, the conventional well test results are included for comparison with those of the current method. It only requires a few simulation runs for the current procedure to obtain the well test results.
The interference case shows that the pressure data of the observation well during injection and shut-in periods at an active well are matched by the current method, The analyses by conventional methods can only be conducted during either the build-up or the shut-in period. In the multi-layered case, with crossflow at the wellbore between the high and low permeability layers, the current method is capable of determining the permeabilities of these layers individually. In contrast, the conventional well test analysis only provides a composite permeability value for a multi-layered reservoir. The current procedure is also applied to the horizontal well test analysis. The horizontal and vertical permeabilities are analyzed simultaneously.
A procedure of well test analysis using a reservoir simulation model coupled with a history matching program has been developed, The history matching program used in this study is called "Adaptive History Matching (AHM) System" which was developed by Scientific-Software Intercomp (SSI) with the participation of Texaco and two other major oil companies. AHM was designed to help the engineer deal with the problems of history matching reservoir performance data with a reservoir simulator. Pressure data measured in well test is directly history matched with the current method without converting to dimensionless terms or taking the logarithm of the data.
The history matching system used in the current procedure is based on Bayesian inference. Bayes’ theorem provides a process of learning from experience and shows how knowledge about the state of nature can continually be modified as new data becomes available. Four cases of well test analysis are presented in this paper. They include a single well test, an interference well test, a multi-layered reservoir case, and a horizontal well test. In each case, the conventional well test results are included for comparison with those of the current method. It only requires a few simulation runs for the current procedure to obtain the well test results.
The interference case shows that the pressure data of the observation well during injection and shut-in periods at an active well are matched by the current method, The analyses by conventional methods can only be conducted during either the build-up or the shut-in period. In the multi-layered case, with crossflow at the wellbore between the high and low permeability layers, the current method is capable of determining the permeabilities of these layers individually. In contrast, the conventional well test analysis only provides a composite permeability value for a multi-layered reservoir. The current procedure is also applied to the horizontal well test analysis. The horizontal and vertical permeabilities are analyzed simultaneously.
Coupling a reservoir simulator and a history matching program proves to be a powerful tool for well test analysis. The new procedure provides fast, straightforward results of reservoir parameters, such as permeability, skin factor, porosity, etc. Furthermore, since the new procedure is based on reservoir simulation, the analysis is applicable to complicated reservoirs and non-ideal well tests.
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