3D Extended Reach Drilling in Soft Sediments with Precise Wellbore Placement for Optimum Recovery

Abstract

Abstract The Adanga Field was discovered in 1974 and is located offshore Calabar in the central part of OML-123 in Nigeria territorial waters. Addax Petroleum took over operatorship of the fields in 1998, when the production from Adanga was just 2,000 BOE per day. Through introduction of new technology, field production increased to over 20,000 BOE per day by 2009. Poor productivity and increasing water cut is an issue in Adanga. Re-interpretation of 3-D seismic data and incorporating additional information from new wells 3-D reservoir modeling confirmed an economic hydrocarbon pool to the west of Adanga (ADW). Additional reservoir targets were identified in the Adanga South field. The plan was to develop these reservoirs from existing infrastructure. Unfortunately, the existing Adanga South platform had no remaining slot capacity to drill new wells without additional infrastructure investment. Upgrading the platform with additional drilling slots was deemed uneconomical, unsafe and will increase collision risk. The platform on adjacent field, Adanga South West, did have drilling slots available, so it was decided to investigate the feasibility of drilling extended reach wells from the Adanga South West platform to access these otherwise stranded reserves in the Adanga South field Challenges in drilling these wells include the weak nature of the formation which can pose difficulties to conventional directional drilling techniques, wellbore quality and ECD management. This paper describes the planning, engineering and execution of constructing two; complex, 3D, horizontal, extended reach wells drilled on the Adanga Field in 2010 to access locked-out reservoir in adjacent field. Using the experience from these two wells, the challenges of drilling complex, high angle wells in the weak sediments of the Niger Delta will be discussed along with how these wells were ultimately drilled and geologically positioned for optimum recovery.