Publications

The Paciran (Mundu) carbonate which is a reservoir in the Sirasun field in the Kangean block was deposited in a ramp-type platform depositional environment. This Paciran reservoir exhibits variation in facies and properties, with lithologies ranging from very fine- grained marl and wackestone to permeable packstone and grainstone. The primary constituent of these permeable packstones and grainstones is globigerinid foraminifera with a smaller matrix content of lime mud. Three horizontal development wells have been drilled targeting the grainstone facies layer, which has good porosity and permeability. The main challenge drilling these wells was to land and steer the well inside relatively thin grainstone facies layer. The thinnest target is approximately 5 to 7 ft true vertical depth (TVD). There were other challenges due to limited offset well data, such as uncertainty in lateral facies distribution and depth. This was the first development campaign in the Sirasun field, so it was run without any prior knowledge of horizontal drilling. A feasibility study suggested the electromagnetic based reservoir mapping while drilling service. This technology would be able to map the remarkable marker boundary before penetrating the target zone and accommodate any change while drilling by using actual marker occurrence. The combination of the reservoir mapping while drilling service inversions, with near-bit measurement and high-resolution formation resistivity image has led to a successful geosteering process placing the wellbore inside the target layer in this drilling campaign. Furthermore, this combination of reservoir mapping while drilling service which capable of mapping reservoir along the wellbore and high-resolution formation image provided a deep understanding of facies distribution with a detailed information of reservoir geometry. The successful application of reservoir mapping while drilling service on this project contributed to the well deliverability by optimizing the well placement in the production section and saving potential cost by eliminating a pilot hole or side track.