New Completion Methodology to Improve Oil Recovery and Minimize Water Intrusion in Reservoirs Subject to Water Injection

Abstract

Water injection during the early stage of a new reservoir's development is gaining popularity around the world. This is especially true in Saudi Arabia where water injection is used to improve oil recovery and for pressure maintenance by placing short or long horizontal water-injection wells around the reservoir flanks. For cases where water-injection wells are placed in reservoir flanks, some of the producing wells are perforated transversally oriented to the water-injection wells to improve the oil recovery around the involved areas. For this specific exploitation strategy, there is a potential risk of water channeling from the injector to the producing well toe which, once it happens, might jeopardize recovery efficiency. For the referenced exploitation strategy, a new completion methodology considering the placement of a fracture barrier at the toe of the producing well to delay water intrusion and improve recovery efficiency is proposed. This paper discusses the process to create the fracture barrier and the benefits of the completion methodology supported with extensive simulations for the different scenarios. Introduction Water injection as a means of improving recovery in oil-producing reservoirs is common. In Saudi Arabia, for instance, water injection has been proven effective in sustaining bottomhole pressure of solution-gas reservoirs for many years. More recently, a typical field would comprise water-injection horizontal wells placed around the flanks of the reservoir with horizontal, transversal producing wells, like the one from Central Arabia. A potential problem, however, with large-scale water flooding and pressure-maintenance projects is water breakthrough resulting from poor sweep efficiency caused by high-permeability layers in the reservoir and/or a high-mobility ratio. Water breakthrough can lead to early abandonment of unswept portions of the reservoir because of the increased operational costs involved in producing, workover, separating, and reinjecting the water. Commonly applied solutions for remediation of early water breakthrough have involved extensive engineering efforts. First, diagnosing the breakthrough mechanism to determine the cause of water breakthrough often requires production logging, monitoring produced water for tracers, drilling monitor wells, cement evaluation, and reservoir simulation. Then, remediation techniques, such as sealants, permeability modifiers, cement squeezes, side tracking, choke-setting reduction, or abandonment, are applied. In some cases, modifying the injection program can lead to some success if it has been determined that the water is coming from a nearby injector. These solutions can also be costly in some cases and will often act to temporarily arrest water encroachment because these treatments are applied most often to the near-wellbore area of the offending producer.

Altering Sweep Profiles during Waterflooding Using Near-Wellbore and Deep Reservoir Controls

“…However, control of flood-front breakthrough has been limited to near-wellbore controls such as in the use of inflow control devices (ICDs) (Fig. Sierra et al (2010) proposed the use of nonconductive barrier fractures (NCBF) in horizontal well completions to alter the flow of fluid within a reservoir (Fig. 2), and conformance treatments.…”