Laminated Sands: An Assessment of Log Interpretation Accuracy by an Oil-Base Mud Coring Program

Abstract

ABSTRACT An assessment of log interpretation accuracy in laminated sand/shale intervals of selected Malay basin formations has shown excellent overall agreement to core derived standards of hydrocarbon pore volume. In the reservoirs studied the log interpretation indicated 4.7% less original oil-in-place overall. Log calculated hydrocarbon pore volume ranged from +2 to −18% of the core derived values in individual reservoirs. Accurate and precise standards of hydrocarbon pore volume were derived from a coring program that required the development of an oil-base mud system, closely monitored drilling and coring operations, totally integrated logistics and pertinent core testing procedures. Extensive quality control measures comprising mud system monitoring by interfacial tension measurements, chemical tracing of the mud system, invasion studies by core layering tests and core analysis procedures were implemented to validate the core data. Representative core porosity and saturation data were weighted to emulate logging tool response. The simulated log responses were compared to actual log responses to identify and quantify intervals of difference.