Capital Efficiency Improvement of an Infill Water-flood Project of a Clastic Reservoir Field in South of Oman
Authors: Al-Rawahi Zainab , Al Hadhrami Waleed , Hussaini Azza , Sengupta Sanjoy , Dabbagh Raied , Nofli Sami , Kharusi Balqees , Hadhrami Abdulrahman , Habhouba El Hafed , Al-Rawahi Ashwaq , Velazco Quesada Conny , Mathew Benoie Parappallil , Oreagba Temitayo , Al-Ghannami Mohammed , Al-Harthy Saif , Van Berkel Jasper , Al-Mahrooqi Majid , Al-Hinai Suleiman 
Published: October 2022

Abstract
Unlocking future development opportunities for brown fields are deemed to be a challenge from Urban Plan (UP) prospective. A field "A" of this paper subject is located south of Oman and was discovered in 1956. The reservoir in this field is a clastic formation divided into two main units; A and B, separated by a 10-15m thick lacustrine shale. The field is an onshore and is under waterflood since 1990s. The development of this paper subject was initially coupled with a nearby Field in the same cluster "Field B" for infill waterflood followed by polymerflood concept. The field development plan (FDP) calls for infill drilling in Inverted "9-spot" patterns with tighter well spacing in the Unit-A, convert corner Oil Producer (OP) to Water Injector (WI) and this development is to be associated with a totally new Urban Plan "revamp" that requires a demolition of the existing facilities. It also called for developing Unit-B through dedicated (twin) wells instead of comingling with Unit-A (to be supported by field trials). Moreover, selectively abandon horizontal producers in mitigating collision or interference risk with infill wells and to De-risk the full field polymer development through a new dedicated polymer pilot using new polymer molecular weight based on core flooding experiments data. The project was parked in 2014 at Decision Gate 3b (DG3b) because it was not economic with a very high Unit Technical Cost (UTC).
Since then, great efforts were made by the Asset team to drive project competitiveness and be able to mature the project. Main steps achieved were; 1) de-risking/validating infill development concept by accelerating part of the FDP drilling scope utilizing the existed facility with very attractive economics; which unlocked an alternative full field urban plan concept of retrofitting instead of revamp resulted in drastic drop of project UTC, 2) Completing FDP proposed field extension appraisal scope (added additional 63 infill well locations), 3) Optimizing Water Treatment Plant (WTP) scope utilizing available field historical injection data, 4) Proposing Integrated Project Contracting Strategy (IPM) for drilling project wells to reduce drilling cost, 5) Proven comingling concept of Unit-A and B instead of twining through a dedicated pilot and 6) Successfully de-risked full field polymerflood development through a two years dedicated pilot. All these steps have led to successfully mature the project to Final Investment Decision (FID) in Q3 2020.
This paper will demonstrate the key development challenges and risks, key steps made to validate/de-risk the proposed concepts before the full field implementation and the capital efficiency Journey to improve project competitiveness through an integrated subsurface and surface efforts.