A Procedure for Integrating Geologic Concepts into History Matching

Abstract

Abstract This paper describes a history match study carried out on a deep water reservoir with roughly a year of production history, consisting of flowing bottom hole pressure (FBHP) and oil rate measurements. This study demonstrates a procedure that can be used to integrate geologic concepts with the history match process to find a range of geologically realistic reservoir descriptions that are all consistent with production history to date for evaluating uncertainty in predictions. The process has three steps: 1) determine, based on geologic and engineering data, what model inputs will be tested in history matching; 2) develop an experimental design(s) and use it(them) to test the impact of those inputs on reservoir performance; and 3) select models for further history match work or prediction of future performance. Two geologic features were selected for study: The degree to which the boundaries between stratigraphic elements seal. Analysis of seismic data identified three levels of stratigraphic elements - channel complex sets, channel complexes, and channel complex remnants. Degree of sealing represents the presence of sub-seismic shale drapes at each level. The degree to which faults are sealed, which depends on the net-to-gross ratio and the throw of each fault. The degree to which a given fault seals is uncertain because it depends on the detailed spatial arrangement of sand and shale in the fault zone, which is not measured directly. The impact of shale drapes was evaluated first. Four shale drape scenarios were chosen to represent a range of behavior including the best match, and seven fault seal scenarios were used to further evaluate the impact of fault seal. Our analysis in this case revealed that the pressure depends on both fault seal and shale drape continuity, with the best matches observed when either faults or stratigraphic boundaries are partially closed and the other geologic feature is open. This allowed selection of seven reservoir descriptions for use in predictions.