Abstract
South Lokichar basin is located onshore Kenya, and multiple oil fields in this basin have been discovered since 2012. The discovered fields are characterized by complex subsurface geology, high clay content mineralogy, waxy oil, and low formation water salinity. The basin is located in a remote, semi-arid area with no existing oilfield infrastructure. To address a previous unsuccessful water injection trial, a follow-up pilot project was sanctioned in 2016 to prove water injection in these fields to de-risk the full-field development. The pilot project had three main objectives:
Prove injectivity in the Amosing and Ngamia, the two main fields of South Lokichar basin.
Understand formation damage mechanisms to optimize water injection.
Qualify Turkwel River dam water, the current preferred source for use as makeup injection water.
A project team comprising in-house subject matter experts, service company representatives, and independent consultants was established. An integrated water injection, flowback, and wireline package was planned, and well completion and other auxiliary equipment were sourced and mobilized to the project area. Project delivery was assured through a multidisciplinary review of potential formation damage mechanisms and a comprehensive design and planning process to select the proper chemical treatments to resolve formation damage. A laboratory testing program and reviews of previous injection trial performance were key planning activities to help ensure success of the project.
The project was completed with no lost time incidents during the total duration of 15 months, from concept to completion. The project was successfully delivered under strict budgetary constraints, with a number of logistical, downhole equipment, and reservoir performance challenges that had to be overcome during the execution phase.
Injectivity under both matrix and fracture conditions was achieved into ten zones across three candidate wells in the two main fields. This was accomplished by pumping an engineered selection of pre-injection heated chemical treatments to prepare the well for the primary hot water injection stages. Water sourced from both a ground water borehole and the Turkwel River dam was filtered, chemically treated to injection quality, and finally heated to ~90°C before injection into the zones of interest.
Execution efficiency was enhanced through real-time monitoring and troubleshooting from operating company and service company offices, where 24-hour engineering support was provided.
This paper presents the challenges experienced and solutions applied to successfully prove injectivity into the reservoirs of South Lokichar basin. It further offers a proof-of-concept for the use of hot water injection and engineered heated pre-injection treatments for formation damage prevention and remediation to help improve well performance in these waxy oil reservoirs. The methods and learnings developed can be applied to similar reservoirs, both in the same region and worldwide.
