Publications

North Belut field is located in the Block B South Natuna Sea – West Natuna Basin. This field is mainly producing gas with some oil and condensate accumulations from stacked sand deposited in fluviodeltaic environments. Multiple fluid contacts with varying reservoir thickness and depleted zones are common. The geological characteristic in North Belut field becomes more complex with the presence of low water salinity and reservoir compartmentalization. It often results in misleading fluid identification if only conventional petrophysical data is used. North Belut field requires more data acquisition and measurements due to its reservoir characterization complexity since conventional petrophysical analysis from triple-combo logs is not enough. Therefore, the pressure measurements and downhole fluid identifications are required to update petrophysical model, determining fluid types and contacts, also as input for reservoir simulations and perforation interval selections. These information need to be acquired to optimize the upside hydrocarbon potential in North Belut field. Therefore, the fit and purpose technology such as formation tester is required to answer formation evaluation challenges in North Belut Field. The formation tester is used to measure and monitor the formation pressure, including reservoir pressure depletion, as well as determining fluid types and contacts. This information can be acquired either by using wireline formation tester and/or formation pressure while drilling. Both of these methods have its own advantages as the wireline formation tester have more advanced sensors to identify fluid type and obtain fluid samples, while formation pressure while drilling is more suitable for difficult or harsh drilling environment and highly deviated wells. In this paper, the key factors on selecting the wireline formation tester and/or formation pressure while drilling for challenging formation evaluation in North Belut field are discussed. This includes the application of formation tester results to update the petrophysical model, well correlation, and reservoir model. Also, the experience from recent wireline formation tester and formation pressure while drilling acquisitions are discussed as lessons learned for the next logging operation in North Belut field.