Using New Intervention-less Surveillance Technology to Optimize the Implementation of Waterflood

Abstract

Abstract The value of implementing intervention-less downhole surveillance technology lies in early assessment of field-scale reservoir performance and well deliverability in South Oman's largest waterflood development. Such technology can aid in assessing whether aquifer support by means of (controlled) fracture injection is achievable, which is potentially more valuable than matrix injection to enhance oil production. At the same time HSSE exposure and deferment will be reduced by avoiding well interventions. This paper will share learnings from Distributed Fiber-Optic (FO) Sensing technology. More specifically, this paper will present the case study of field ‘A’, where waterflood is being operated in two methods based on sectors depending on field geological and reservoir properties: ‘Deep’ water injection in the aquifer, under fracture conditions ‘Shallow’ water injection close to the oil-water-contact (OWC), under matrix conditions ‘Deep’ water injection minimizes the risk of early water breakthrough, but it delays the aquifer pressure support which in turn means lower offtake. The ‘Shallow’ water injection (trialed by injecting water 50m below OWC) has a higher risk of water short circuiting, accelerates pressure support and thereby enhances production / well deliverability. Fiber-optic data is part of a decision-based surveillance program, which also included injection / production logging via PLT, step-rate tests, and pressure monitoring. The time-lapse data has illustrated some fracture growth up- and downwards of the perforation interval in most wells but is still contained below the OWC. In some wells, the injection growth is also controlled by the presence of several intra-reservoir shale baffles that are acting as barriers to vertical communication and thereby delaying the injection response while inducing a strong pressure response in nearby producers. The data has helped to further calibrate and validate the model assumptions and will help in optimizing the waterflood development concept for the field. Proactive interventional-less surveillance enables monitoring of the zonal injection conformance, provides advantage of learning reservoir performance and supports agile WRFM operations and decision making. Furthermore, cost competitive and credible technology have made PDO a front runner to keep subsurface risk at as low as reasonably practical levels and boost oil production. This distributed fiber optic sensing technology provided cost-effective, fit-for-purpose, and intervention-less well-and-reservoir surveillance.