Eliminating Associated Gas Flares in The Nigerian Stranded Marginal Field Oil Fields: The Otakikpo Field Strategy

Abstract

The Otakikpo marginal field was carved out of OML 11 and is situated in the southern part of the license. The field was discovered with Otakikpo-02 in 1983 and was further appraised with Otakikpo-03 in 1986. The wells encountered hydrocarbons in 4 stacked oil and gas bearing sands (C5000, C6000, C7000 and E1000). The field is operated by Green Energy International Limited (GEIL). The field currently produces ~10,500 bopd with significant associated gas (AG) production from the wells with average GOR of ~1000 scf/bbl. Compositional analysis shows that the associated gas is rich in C3 – C4 components (~ 8%) and C5 – C7 (~ 3%) making it ideal for NGLs (LPG and condensates) extractions. Most natural gas utilization projects require securing constant gas production contracts for between 10-20 years and for constant rates > 50 MMSCFD. However, the Otakikpo field, the associated gas reserves do not meet this threshold and the production profiles are at best unpredictable. To address these issues, an innovative strategy is required to accelerate reduction in the field's AG flaring. A qualitative and quantitative screening of the various gas utilization concepts against some critical decision drivers (AG production profile, scalability, CAPEX) led to the recommendation of a modular LPG extraction plant for the heavier components of the AG and Gas to Power for the lean gas. The conventional approach of piping gas from a remote field needs to be replaced with a less orthodox technique of "bringing the plant to the gas". This eliminates the need for expensive pipeline and compression since the facility is within the Otakikpo field flow station. Furthermore, a modular scalable strategy with small footprint plant that is quick to deploy and easy to relocate was recommended as the best solution for the field. The Operator successfully commissioned the 12MMSCFD modular LPG extraction plant and 6MW power generating plants. This scale of modular LPG plant will be the first to be installed in the country. This strategy could be adopted by other small fields in addressing AG flares caused by stranded pockets of gas located in oil fields in the Niger Delta thus supporting the Government's aspiration of eliminating AG flares.