Sequence stratigraphic interpretation methods for low-accommodation, alluvial depositional sequences: applications to reservoir characterization of Cut Bank field, Montana

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Title: Sequence stratigraphic interpretation methods for low-accommodation, alluvial depositional sequences: applications to reservoir characterization of Cut Bank field, Montana
Author: Ramazanova, Rahila
Abstract: In South Central Cut Bank Sand Unit (SCCBSU ) of Cut Bank field , primary production and waterflood projects have resulted in recovery of only 29 % of the original oil in place from heterogeneous , fluvial sandstone deposits . Using highresolution sequence stratigraphy and geostatistical analysis , I developed a geologic model that may improve the ultimate recovery of oil from this field . In this study , I assessed sequence stratigraphic concepts for continental settings and extended the techniques to analyze low -accommodation alluvial systems of the Cut Bank and Sunburst members of the lower Kootenai formation (Cretaceous ) in Cut Bank field . Identification and delineation of five sequences and their bounding surfaces led to a better understanding of the reservoir distribution and variability . Recognition of stacking patterns allowed for the prediction of reservoir rock quality . Within each systems tract , the best quality reservoir rocks are strongly concentrated in the lowstand systems tract . Erosional events associated with falling baselevel resulted in stacked , communicated (multistory ) reservoirs . The lowermost Cut Bank sandstone has the highest reservoir quality and is a braided stream parasequence . Average net -to -gross ratio value (0 .6 ) is greater than in other reservoir intervals . Little additional stratigraphically untapped oil is expected in the lowermost Cut Bank sandstone . Over most of the SCCBSU , the Sunburst and the upper Cut Bank strata are valley -fill complexes with interfluves that may laterally compartmentalize reservoir sands . Basal Sunburst sand (Sunburst 1 , average net -to -gross ratio ~0 .3 ) has better reservoir quality than other Sunburst or upper Cut Bank sands , but its reservoir quality is significantly less than that of lower Cut Bank sand . Geostatistical analysis provided equiprobable representations of the heterogeneity of reservoirs . Simulated reservoir geometries resulted in an improved description of reservoir distribution and connectivity , as well as occurrences of flow barriers . The models resulting from this study can be used to improve reservoir management and well placement and to predict reservoir performance in Cut Bank field . The technical approaches and tools from this study can be used to improve descriptions of other oil and gas reservoirs in similar depositional systems .
URI: http : / /hdl .handle .net /1969 .1 /ETD -TAMU -1127
Date: 2009-05-15

Citation

Sequence stratigraphic interpretation methods for low-accommodation, alluvial depositional sequences: applications to reservoir characterization of Cut Bank field, Montana. Available electronically from http : / /hdl .handle .net /1969 .1 /ETD -TAMU -1127 .

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