Successful Application of Thin Bed Petrophysical Evaluation Workflow in Deep-Water Turbidite Environment: Case Studies from Fields Offshore Malaysia

Abstract

As the demand for energy increases, oil companies are moving further offshore in their search for hydrocarbons in previously untouched deepwater reservoirs. In a deepwater turbidite depositional environment, high net to gross reservoirs are often overlain by a significant thickness of low net to gross sandshale sequences. While conventional formation evaluation, performed using standard resolution logs, is sufficient to characterize the thick high net to gross beds, it tends to underestimate and often fails to realize the true potential of the low net to gross thinly bedded intervals. These thin bed packages, by themselves, can contain significant amount of hydrocarbon. Clearly an alternative method of evaluating log data in thinly bedded reservoirs is required for accurate assessment prior to commercialization. This paper presents case studies from several deepwater turbidite fields offshore Malaysia, where a thin bed petrophysical evaluation workflow has been successfully applied. The study was conducted as part of an integrated study to improve understanding of thin bed potential in terms of its distribution, lateral continuity and production capacity. The thin bed petrophysical evaluation workflow starts with a conventional formation evaluation; followed by constrained log-resolution enhancement processing; an enhanced resolution formation evaluation; cutoff selection for pay determination; and ends with core and formation tests calibration and validation. The results from the conventional and thin bed evaluation are compared to and validated by: core photographs; core x-ray diffraction analysis (XRD); routine core analysis of porosity, permeability and saturation; and formation test data. This paper concludes by highlighting some of the important advantages of using the thin bed petrophysical evaluation workflow proposed, these include general and specific observations on: net to gross; saturation; volume of clay; porosity; and permeability. Finally recommendations are made suggesting logging programs to obtain optimal results from this thin bed petrophysical evaluation technique. Overall, this paper hopes to serve as one of main references for thin bed petrophysical evaluation in similar environment.