Retrofit Gas Lift Deployment for Oil Production Optimization in Onshore Niger Delta: A Case Study of EROTON E & P Oil Fields

Abstract

OML 18, operated by Eroton Exploration and Production Company (EROTON E&P) and located within the Coastal Swamp of Eastern Niger Delta contains several producing fields. As a brown asset with over 50 years historical production and ageing infrastructure, rapidly declining oil production caused by rising water cut and depleting reservoir pressure has become a normal feature for most of the reservoirs in the block. There arises therefore, urgent need to maximize the value of these mature fields by deploying fit for purpose and cost-effective technologies and methods. Thus, we deployed artificial lift technique using the abundant associated gas resources within the asset as one method of managing the rapid decline in oil production. Gas lift is a robust and inexpensive artificial lift solution which can be deployed at any period in the life-cycle of a well. The natural reservoir energy to move liquids to the surface through a well at expected rates declines with production time. Changing well and reservoir conditions, such as declining pressure, increasing gas liquid ratios and rising water cut can make consistent and predictable oil production a challenge. A review of the entire wells portfolio within the asset enabled an identification of all potential candidates with potential to benefit from gas lift installation. This was followed by feasibility studies to establish a connection between the magnitude of expected oil resources to be added, the oil rate potential, the existing completion status and surface facility equipment availability such as compression, gas lines and scrubbers etc. Screening of identified opportunities, often conducted in multi-disciplinary review sessions, yielded ranked list of opportunities for further maturation through design, execution and operation. Three (3) fields with over 60 wells and 38 developed reservoirs were selected for the review. The screening criteria included but not limited to reserves to be added, ease of execution, economics and regulatory approval requirements. Since these wells were not originally equipped with gas lift mandrel, alternative means of deploying gas lift equipment downhole had to be designed and implemented. Considering the advanced age of most of the wells, due consideration was given to well integrity in the final execution decision. Despite inherent challenges, EROTON was able to successfully deploy in-house technical knowledge and experience to embark on rigless well intervention campaign to restore production using retrofit gas lift equipment in existing wells, which have ceased to flow due to vertical lift issues, thus extending the life of the wells. We have successfully performed a safe and commercially viable production restoration exercise, returning a total of twelve (12) wells back to full production potential and achieving the well intervention objectives. The operation has accelerated production adding over 5,000 bopd. This paper will discuss the concept of brown field life extension through retrofit gas lift, the workflow utilized and results from select field examples. Well BAKU-07 in RAMA field is further discussed as one of the candidates successfully restored via this method.