First Marginal Deepwater Field Development: Maximizing Learnings and Probability of Success (POS) for Downhole Sand Control

Abstract

The company has extensive experience in holistic sand control and solid management for shallow water environment. Application to near-future marginal deepwater project called L-B cluster requires higher considerations on subsea umbilical, risers, and flowlines (SURF) integrity and long term well performance due to the high-cost environment. Representative field samples (e.g., cores, drill stem test (DST data) to study rock mechanics is scarce with limited in-situ stresses calibration information. This paper presents the workflow undertaken by team to de-risk and establish the downhole sand control design for both oil producer (OP) and water injector (WI) covering design, installation, and production operations philosophy. The workflow started with an extensive multidisciplinary analogue field study covering regional geological study on sand correlation to determine correct reservoir analogue as well as the deepwater fields sand control best practices and lesson learnt. Since the analogue field already have production, the study was extended to cover the production impairment impact trend and the implementation approach to derisk the field attainability target. Based on geological and geomechanical understanding, L-B regional deepwater formation characteristics with interbedded sand and shale formation does not suit certain types of sand completion methodology, as it introduces additional risk: Deformation of expandable sand screen due to the different expansion rate of sand and shale during depletion, creating weak points in which sand is mobilized into the screen tears resulted from deformation Uneven proppant placement in cased hole frac pack for OP Loss of active sand control for a cased hole frac pack and open hole gravel pack in WI due to proppant flushed away which can be further exacerbated by uneven placement This resulted in the following lower completion strategy: Open Hole Gravel Pack (OHGP) for OP and Open Hole Stand Alone Screen (OHSAS) for WI Allowance for backflushing in WI to remove screen plugging while managing risk of reverse flow impact Sufficient rathole and long horizontal well completion as dampener to minimize magnitude of water hammer/adverse reverse flow impact in WI. For detail design, team devised comprehensive laboratory analyses covering Particle Size Distribution (PSD) and Sand Retention Test (SRT) inclusive of geomechanics modeling work for screen sizing and estimation of fines production through screens. Result is then used to devise method to minimize and manage fines production in SURF and topside. The holistic approach of sand control workflow is compulsory for marginal deepwater development, since the environment is less forgiving during production due to the massive cost of well intervention/troubleshooting and production associated issues; flow assurance and facilities turn-down limit, therefore downhole sand control and operation should be robust enough to cater throughout the life of the field.