Publications

Kokoh Field and Kelok Northeast (NE) Field are two recent discovery fields in the Central Sumatra Basin, Indonesia. Due to limited exploration well data and remote field locations which preclude additional exploration due to high capital expense, the decision to drill development wells requires management of key subsurface uncertainties that could result in marginally or uneconomic development investment in the case of low-side uncertainty outcomes. In order to manage this risk, the information from available exploration wells and surveillance data are identified to resolve subsurface uncertainties that have the greatest impact on development outcomes. The information are production surveillance data from exploration wells including single-completion versus commingled production streams per well, reservoir pressure, fluid analysis, wellbore integrity and facilities flow assurance that enable characterization of development well performance forecasts and their uncertainty. This paper describes the approach to, as well as the challenges encountered during, production surveillance from exploration wells in Kokoh and Kelok NE fields. Surveillance and analyses performed include extended single-well production tests, downhole pressure and temperature monitoring, fluid analysis and fit-for-purpose reservoir simulation modeling for dynamic reservoir characterization. During production surveillance, several challenges required management including early water breakthrough, high wellhead pressure, high ESP motor temperature, intermittent pipeline flow and oil congealing, all of which jeopardized the collection of surveillance data. Analysis of the surveillance data set, together with investment efficiency analysis, resulted in the decision to drill a single development well in Kelok NE Field. The production outcome to date is within the forecast reliability range and, therefore, within the expected range of economic outcomes.