Abstract

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 whilst concomitantly reducing any potential damage in both low water cut and higher water cut wells. This paper discusses the technical problems and examines new technologies for treatment of such production wells through their life cycle.

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, it is shown that the new technical area of emulsion scale inhibitor delivery systems, originally designed to control scale within low water cut wells, has application 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 to be 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 multi-lateral wells, sub sea tiebacks and commingled flow present 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 prior to field development/production (CAPEX phase) rather than being confronted in a reactive manner once water breakthrough occurs (OPEX phase). Such an approach allows for the selection of 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 (Figure 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. Figure 2 outlines the scale issues associated with 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 factor to be taking into account when evaluation the risk of scale formation and control are descried in detail along with presently available technologies and the gaps that exist in a recent SPE publication.1

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