Integrated Geological/Engineering Model for Barrier Island Deposits in Bell Creek Field, Montana

Abstract

Abstract Geological heterogeneities controlling fluid production from the Lower Cretaceous Muddy formation in the Tertiary Incentive Project (TIP) and adjacent area in Unit ‘A’ of Bell Creek field Montana were investigated. Production and Injection performance and production test data, as well as core, log, and structural data, were integrated to provide an improved geological/engineering model. The model was used to study the influence of the various scales and nature of geological heterogeneities on fluid flow and residual oil saturation distribution in the reservoir. Information from primary production; initial production rate potential distribution; cumulative primary, secondary, and tertiary production; pressure transient test data; water injection front tracking; electrical resistivity changes due to depletion of residual oil; injectivity histories of injection wells; and areal simulations was integrated to identify fluid flow patterns and residual oil saturation distribution. Production performance and oil saturation distribution in Unit 'A' of Bell Creek field were affected by critical multigenetic heterogeneities, such as stratigraphy and dimensions of facies, valley incisions into the best productive barrier island sediments, high-permeability channels, reduction in net pay due to diagenetic clay content, faulting and structural dip. These heterogeneities result in large production/residual oil saturation contrasts over small distances. Results of the study showed that the most productive part of Unit 'A' is associated with regions of well-developed high-energy barrier island facies (upper shoreface and foreshore); low amounts of diagenetic clay cement; and absence of structural discontinuities. The influence of nature and the scale of geological heterogeneities varied at different stages of oil recovery. The understanding of reservoir performance in the barrier island system was improved by integrated multidisciplinary analyses of standard data and comprehensive approach to geological and engineering interpretation. Introduction This study was performed as part of the continuing research by NIPER to characterize reservoirs developed within barrier island system in terms of geological and production behavior. The integration of geological and engineering models was emphasized. Raw data except core descriptions and petrographic analyses for this study were provided by Gary-Williams Oil Producer Inc.; however, all geological and engineering analyses and interpretations were performed by the authors. Barrier island depositional systems comprise at least six giant oil fields in North America and, therefore, are of considerable economic importance. Major geological heterogeneities encountered in Bell Creek field and their influence on primary, secondary, and tertiary production have been previously discussed. P. 491^