Exploring deeper reservoir potential in east Balingian basin, offshore Sarawak

Abstract

East Balingian province is part of the bigger Balingian basin of offshore Sarawak. It is a proven petroleum system, with more than 10 oil and gas fields producing in present day. With more wells drilled, more hard data from the fields are made available from core and cutting samples. These are the main tools in understanding the reservoir better, especially its facies type and what is controlling the reservoir quality in terms of porosity and permeability. This understanding of facies is then crucial to determine the prospectivity of the unexplored deeper structures within the East Balingian basin. There are 23 wells data used in this study that includes petrography, XRD, geochemical, DST, well logs, pressure and temperature data. However, only two wells were drilled deeper than 2500 meter subsea. From porosity plot with depth, it was observed in general that porosity decreases with depth, at which the critical porosity floor is at 2200 meter subsea (porosity mostly lesser than 10%). The study found that the reservoir quality was mainly controlled by mechanical compaction, overpressure, temperature, chemical diagenesis that formed diagenetic minerals surrounding grains surfaces and in the pore throat, facies grain sizes and clay content of the reservoir rock. It was observed that reservoir quality for depth deeper than the 2200 meter subsea can be preserved by having overpressure, bigger grain sizes and lower clay content (volume of shale value less than 15%). This makes deeper reservoir prospectivity potential possible in the East Balingian basin, which currently still remains underexplored. This ability to predict reservoir quality may also assist reservoir engineers to predict reservoir flow rate, recovery factors and production profile beforehand, which are needed to deduct whether the fields are economic to drill or not. This will then lead to an increase of hydrocarbon reserve in Malaysia and contribute to the economy of the country.