Karst Mapping on Carbonate Build up Using Advanced Spectral Decomposition and Enhanced Variance Filter Technology at Offshore Malaysia

Abstract

Abstract Karstification is one of the major culprits for drilling issues (e.g., mud loss/blowout/wellbore collapse) in carbonate fields. Hence, it is crucial to precisely identify and predicate paleokarst distribution before formalizing a drilling plan. In this study, an isolated Miocene carbonate buildup in the offshore of Malaysia which is covered by a 3D marine seismic survey is selected for Karst mapping. Geological study shows that the carbonate buildup is bounded by two boundary faults and carbonate bodies were altered by multiple episodes of faulting and subaerial exposure related karstification. Extensive karstification is also evident by total mud losses in wells penetrating carbonate succession. Two in-house technologies: Advanced high-resolution Spectral Decomposition (ASD) and Hessian Filter-enhanced Variance (HFV) were used to illustrate the discontinuities within carbonate bodies and map Karst distribution. Well calibration with ASD and HFV results demonstrates that 1) Carbonate buildup can be clearly distinguished from surrounding clastics by specific (bright orange-colored) boundaries against dull colored clastics in RGB blending images; 2) Karst-related cavernous systems can be depicted by dendritic pattern variation in ASD images and HFV anomalies; 3) Linear discontinuities caused by fractures/faults are also highlighted by the results of ASD and HFV. It can be concluded that the combination of discontinuities revealed by ASD and HFV and with appropriate well and core calibration is a reliable way to predicate karstified reservoirs within the offshore carbonate buildup.