Advanced Thin Bed Evaluation to Unlock Hydrocarbon Potential in Offshore Malaysian Fields

Abstract

Abstract A significant fraction of the reservoirs across the world as well as in East & West Malaysia consist of thinly bedded deposits in Fluvial, Deltaic, Deep-water sediments and Channel system. It is estimated that approximately 30-40% of hydrocarbon in place resources are deposited in thin laminated reservoirs that typically laminated formation with sand and shale alternate layers. These thinly bedded reservoirs have lots of hydrocarbon potential which cannot be evaluated by conventional logs, thereby causing underestimation of reserves. This paper presents a new technique to unlock hydrocarbon potential reserves in thinly bedded reservoir using an innovative high-resolution technology (HiRes). The workflow consists of two main steps: first, to create HiRes resistivity log from conventional deep resistivity and high resolution (resistivity image) log, and second, to generate high resolution density and neutron log utilizing HiRes resistivity log created in earlier step. Then standard petrophysical workflow to compute porosity and water-saturation can be continued with developed HiRes resistivity, density, and neutron logs. Currently this workflow has been developed on resistivity image logs, such as Oil Based Mud Imager (OBMI) or Oil Mud Reservoir Imager (OMRI) typically run-in wells drilled with oil-based mud. This new technique was then tested in few wells from different offshore fields having different environment of depositions, in the East and West Malaysia basins. The HiRes technology has been tried on many wells in various Malaysian fields. Those wells were selected based on the available complete well-log suite data including its core data. The outcome processed logs were then verified with the core-laboratory analysis results i.e., with routine core analysis (grain density, porosity, permeability), and with Dean Stark analysis for water saturation. The results showed remarkable results thus proving the robustness of the technology. A non-pay is reinterpreted as pay zone using this technology thus enhance the volume estimation. The HiRes technology provides behind casing perforation opportunity as the new zones could be added which were considered as non-pay by conventional methods. Since HiRes method produces high resolution resistivity, density, and neutron curves, and thereby provides better lithology and bed boundary definition. The HiRes, an innovative in-house technology, not only addresses the problem in thin beds but also provides quantitative petrophysical solution of thinly bedded reservoirs which aligns with the core results. Consequently, HiRes certainly improves the accuracy in the geological interpretation and resulting geological model.