Combined Uncertainty and History-Matching Study of a Deepwater Turbidite Reservoir

Abstract

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 160171, ’Combined Uncertainty and History-Matching Study of a Deepwater Turbidite Reservoir,’ by Akshay Aggarwal, SPE, Song Du, SPE, and Michael J. King, SPE, Texas A&M University, prepared for the 2012 SPE Annual Technical Conference and Exhibition, San Antonio, Texas, 8-10 October. The paper has not been peer reviewed. The authors used historical field data from a deepwater turbidite reservoir to investigate several history-matching strategies. This project involved an integrated seismic-to-simulation study. The trade-offs between exploring many models vs. calibrating a single model were explored. The scale at which the geologic model was constructed and how the simulation scale could be determined were examined. The large discrete steps in the process and the smaller local assisted parameter calibration were studied. The results provided general guidance on workflow sequence, model selection, and the scales of static and dynamic modeling. Introduction History matching is a process wherein changes are made to one or more parameters of the initial geologic models so that the predicted reservoir performance matches production history. The history match calibrates reservoir descriptions that then may be used for performance prediction and reservoir-management decisions. The initial geologic model represents the reservoir structure, its stratigraphy, layering, sedimentology, and facies distribution. The static model consists of a 3D spatial distribution of porosity and permeability derived from the geologic model. An initial distribution of water, oil, and gas is added to the static model to enable flow simulation. Historical data from the well, injection, and a subset of production provide boundary conditions for reservoir-simulation performance prediction, and the remaining production and pressure data are used to test those predictions. The intent of this study was to emphasize the importance of multiple initial geologic models and to demonstrate an uncertainty-assessment strategy on the basis of multiple geologic interpretations. The uncertainty assessment is a precursor to a full-history-match study. It may be thought of as a means of generating multiple starting points for history-match-model calibration, or, perhaps more importantly, may be used to obtain an improved reservoir description even without full implementation of a history match. An SPE reprint collection (Datta-Gupta, Akhil, ed. 2009. History Matching and Conditioning Geologic Models to Production Data. Richardson, Texas: Reprint Series, SPE.) provides an excel-lent starting point to understand current, developing, and historical practice. This paper describes the history match within an integrated seismic-to-simulation research study, including the interpretation of seismic data, assembly of geologic information, petrophysical log evaluation, and well-test pressure-transient interpretation. The results of this integrated geoscience study were used as the starting point for the history match. Field data for the study were provided by a major producer for research and educational purposes. However, this study was performed without their direct intervention.