Predicting Hydrocarbon Column Height and It’s Uncertainty Related to Semi-Regional Seal Capacity Benchmark in Mahakam Delta

Abstract

Deltaic environment, well known with it’s high net to gross content, which create relatively less favorable setting for hydrocarbon trapping (sealing), often present a difficult problem when it comes to predicting hydrocarbon column height on a prospect in exploration domain. On a Mahakam Delta where shale is the most likely candidate for seal, the sealing capacity of each shale layer tends to vary related to its composition and diagenetic stage. The best way to assess the sealing capacity of the seal layers is to have reasonable amount of core-calibrated geotechnical data taken at shale which is rarely available. On a context where those kinds of data is not available, building a semi-regional benchmark of shale’s sealing capacity in combination with the understanding of the petroleum system history often provides a fit-to-purpose solution. “A” Prospect is defined as a stratigraphic trap on a 3-way closure setting. Even though the closure mapping indicates that it is possible to hold more than 500 m hydrocarbon column, nearby producing fields with similar geologic setting given its inefficient nature of the seal and complex trap filling history, has indicated that it has a very little chance of sustaining such huge column. The quick look back-stripping analysis which indicated that hydrocarbon migration has commenced before the last structuration period has given somewhat more moderate hydrocarbon column estimation. Although the result still give slightly higher estimation given the regional data at hand, compare to 500 m hydrocarbon column, this scenario has higher possibility to occur and was chosen as maxi column case. While the semi-regional benchmarking incorporating nearby producing fields data respecting similarity in term of trap type (3-way closure with fault associated) and stratigraphy has yielded a semi-regional fault sealing capacity trend which later on used as a base for mini-base column case definition. Furthermore, the above technique that has been used to estimate the hydrocarbon column and its uncertainty given the available data has yielded a more reasonable possible range of value that not only respecting the whole petroleum system understanding of the prospect, but also integrating the main factor that control the seal capacity of the nearby producing fields.

AAPG Datapages/Search and Discovery Article #90354 © 2019 AAPG Asia Pacific Technical Symposium, The Art of Hydrocarbon Prediction: Managing Uncertainties, Bogor, (Greater Jakarta), Indonesia, August 7-8, 2019