Abstract
Optimisation of hydrocarbon recovery from mature fields has always been very attractive in the petroleum industry. This will increasingly be of great importance going by the complexity of making new commercially viable hydrocarbon discoveries, and the high cost and long delays of bringing new discoveries into production.
OML100 is a conventional offshore block located 80 km south-east of the Nigerian coast and operated by Total E&P Nigeria in partnership with the Nigerian National Petroleum Corporation (NNPC). It comprises four producing fields, namely: Afia, Edikan, Ime and Odudu; and two other fields which are currently being studied for subsequent development.
Field development started in 1993 with oil production reaching a plateau of 70 MBD between 1995 and 1998. Due to sound reservoir management practices and collaboration with other entities, 39% hydrocarbon recovery has been achieved in the 16 years of production. Today the block faces series of challenges militating against the realisation of more than 50% recovery which is our base case objective. These challenges include: ageing surface facilities, increasing gas and water handling challenges, sand production, loss of wells, insufficient well activation, limited reservoir pressure maintenance, by-passed oil and remaining reservoir uncertainties.
This paper highlights practical multi-disciplinary approaches that are being employed in order to maximise oil production, at minimum cost, from the four fields located in a challenging offshore environment. Reference is made to standard definitions of conventional offshore and mature oil fields. This is followed by a review of the development history, status and challenges of the fields. Methods towards continual optimal reservoir surveillance and exploitation are discussed as a case study and these include: seismic data reprocessing and reinterpretation, review of geological models, update of reservoir synthesis and models, infill development proposals, sand bailing and zone change operations, improved well activation project, surface facilities integrity project, dedicated pressure maintenance and polymer-surfactant injection projects.
