Analysis of a marginal marine, thin-bedded, heterolithic reservoir: Implications for in-place volumes and static connectivity.
Honours Degree 2008
University of Adelaide
This study of the Sunrise-Troubadour fields (offshore northwest Australia) concentrates on a 30m thick interval of predominantly heterolithic strata within the reservoir succession (J28.2 to J28.4). The marginal marine, wave- and fluvial-dominated sediments were deposited over a period of approximately 1.25 Ma, on the delta front, pro-delta and offshore transition zone, within a retrogradational to progradational high stand systems tract parasequence set.
Sequence stratigraphical interpretation and analogue data integrated with sand/shale ratio analyses indicate that depositional environment and stratigraphic architecture affect connectivity. Reservoir continuity in the heterolithic interval of the Sunrise-Troubadour fields is predicted to be best in areas proximal to fluvial input points. Palaeogeographical maps created by integration of sequence stratigraphy, depositional processes and palaeocurrent analysis suggest that fluvial systems were located in the southwest and northeast of the field at the time of deposition.
Calculation of sand/shale and net/gross ratios from detailed core logging results in significantly higher values (averages of 6% and 13%, respectively) than those from analysis of wireline logs. Both sand/shale and cementation percentages increase with increased fluvial influence. Results suggest the potential for a significant volumetric upside in intervals of thinly bedded strata located in the southwest and northeast of the fields.