Abstract: Impact of Mouthbar Correlation Techniques on Recovery Factors, Sirikit Field, Thailand. An integrated 3-D Reservoir Modeling approach.
AINSWORTH, R. BRUCE, MONTREE SANLUNG, S. THEO C. DUIVENVOORDEN, PETER J. COLLERAN, and GERARD H. MAKEL, Thai Shell Exploration and Production Company Ltd.
Production in the Sirikit oil field of the Phitsanulok Basin, Thailand commenced in 1982. The field has a STOIIP of approximately 800 MMbbl. To-date over 130 wells have been drilled in the field and as such it can be classed as being in the “brown field” development stage of its lifecycle. Reservoir management studies into optimising recovery and identifying unswept oil volumes in order to maximise the profitability of the venture are ongoing. This work now involves 3-D static and dynamic modeling. The study detailed below is one such exercise whereby different geological correlation techniques were analysed for their potential impact on recovery factors.
Two mouthbar correlation techniques (lithostratigraphic and chronostratigraphic) were used to generate two different 3-D reservoir architectures using the Shell proprietary 3-D static reservoir modeling system GEOCAP. Significantly different recovery factors are derived from 3-D dynamic flow modeling of these architectures (no vertical upscaling, 2x2 areal upscaling) using the Shell proprietary reservoir simulator MoReS. When sands observed on logs are perforated in both models, the lithostratigraphic (tramline) correlation model results in a 3% higher recovery factor than the chronostratigraphic (dipping) correlation model. This suggests that for this perforation strategy, if a lithostratigraphic correlation model is assumed, an overestimate of recovery factor by 3% will be incurred if the chronostratigraphic interpretation represents the actual subsurface architecture.
The architecture of the chronostratigraphic model additionaly connects thin-bedded toeset sands and shales (which are below log resolution) with thicker upper mouthbar sands. When these thin-bedded heterolithics are perforated a 2% increase in recovery factor is observed over the same model that only has the sands observed on logs perforated.
AAPG Search and Discovery Article #90937©1998 AAPG Annual Convention and Exhibition, Salt Lake City, Utah