Coreflood Studies Examine New Technologies That Minimize Intervention Throughout Well Life Cycle

Abstract

Summary With the development of more and more subsea fields, the challenge for scale-inhibitor squeeze treatments is to reduce intervention frequency by extending squeeze treatment lifetime while concomitantly reducing any potential damage in both low water-cut and high water-cut wells. This paper discusses the technical problems and examines new technologies for treatment of such production wells through their life cycle. This paper covers the findings from late 2001 through early 2002. Because even newer technologies have been developed since the writing of this paper, it should be read as the history of technological development. Scale control technology available to control scale formation within the reservoir and near-wellbore area of production wells will be outlined with a focus on the current developing technology to control scale within low water-cut wells. Moreover, this paper shows that the new technical area of emulsion-scale-inhibitor-delivery systems, originally designed to control scale within low water-cut wells, has applications in both low and high water-cut wells. This study assists in developing an understanding of the mechanism of interaction of emulsion-based products—in particular, the impact of the level of water saturation within the core system. In addition, it demonstrates that the emulsion particles are retained in the core matrix during both crude and brine flowback. This paper indicates that the emulsion product offers the potential for extremely long squeeze lifetimes with minimal damage in oil-production wells with rising water cut. It also demonstrates how different technologies have their own place in the life cycle of a production well. Introduction Flow assurance is an essential aspect of the economic production of crude oil. It can be considered the ability to produce petroleum fluids economically from the reservoir to a production facility over the lifetime of a field. Scale control is one of the key aspects of the flow-assurance issue. The increasing number of subsea fields, together with deepwater production, raises particular issues and evolving challenges for flow assurance beyond those seen for simple vertically drilled wells. The complexity of new well completions in terms of horizontal and multilateral wells, subsea tiebacks, and commingled flow presents particular challenges. Where scale-inhibitor treatments are required for such complex wells, they are often associated with very high intervention costs. Scale control issues need to be addressed as part of asset life cycle management, whereby the issues are tackled before field development/production [i.e., capital expenditure (capex) phase] rather than being reactively confronted once water breakthrough occurs [operational expenditure (opex) phase]. Such an approach allows for the selection of an appropriate economic technology. Indeed, the anticipated problems may influence the plans to develop a field, for example, in terms of water-injection strategies or implementing appropriate technology upon well completion. Scale control within life cycle management is based on varying challenges seen with the increase in water cut as a field and its wells move from dry production to high water cuts. This is associated with four phases of field development—project, plateau, decline, and decommission (Fig. 1). At the project stage, scale control treatment strategies can be developed. The scale issues at subsequent stages depend on the nature and severity of the anticipated scale problem. Fig. 2 outlines the scale issues associated with the injection of seawater into a reservoir with barium and bicarbonate present in the formation water. The process of evaluating the risk of scale in a field under appraisal is briefly outlined below. The factors to be taken into account when evaluating the risk of scale formation and control are described in detail, along with currently available technologies and the gaps that exist in a recent SPE publication (Jordan et al. 2001).

Acid/Scale Inhibitor Stimulation Treatment for High-Temperature CHFP Subsea Wells: Fluid Qualification and Formation Damage Assessment

“…While the frac treatment in this application may certainly alleviate the formation damage associated with small amounts of particle plugging, wettability changes remain a significant concern for low permeability, watersensitive, or low water cut oil wells; large amounts of water pumped during the frac treatment will only exacerbate the wettability change / water block problem. Unfavorable wetting alteration and formation damage associated with chemical reactions between scale inhibitors and formation fluids and rock have been recognized, and a number of alternatives have been proposed to minimize the damage (Jordan et al 1998 and2006;Graham et al 1999;Scott et al, 2000;and Guan et al 2003). Strategies include the use of oil soluble scale inhibitors, aqueous inhibitors in conjunction with relative permeability modifying chemicals, and micro-encapsulated scale inhibitors.…”

Preemptive Scale Management: Treating with Scale Inhibitor While Frac Packing a Well

“…Traditional squeeze treatments have been effective in preventing scaling in the near wellbore region of dry tree completions (Graham et al, 2002a(Graham et al, , 2002b(Graham et al, , 1999; however, subsea wells present additional challenges in terms of limited rig availability and intervention cost. For these reasons, preemptive scale management techniques that can be deployed during the completion operation are very attractive (Jordan et al, 2006). Previous studies by Fitzgerald and Cowie, 2008;Lungwitz et al 2007;Martins et al, 1992;and Vetter et al, 1988 have considered the technical and economic benefits of scale prevention treatment while simultaneously completing or stimulating a well.…”