Life Cycle Management of Scale Control within Subsea Fields and its Impact on Flow Assurance, Gulf of Mexico and the North Sea Basin

Abstract

Abstract This paper presents an overview of life cycle flow assurance management for a platform/subsea development by focusing on scale control. To illustrate this approach examples of scale control methods for deepwater subsea fields will be cited covering aspects such astreatment of the reservoir prior to production to prevent scale formation within the near wellbore (solids and fluid system for inhibitor deployment),downhole scale control using continuous injection (gas lift, capillary), andsqueeze treatments as the production wells move through their life cycle and water cut rises. The management of scale and corrosion issues within a subsea field will be reviewed with examples of an operator moving from combined scale inhibitor/corrosion inhibitor products to single corrosion inhibitor product at the manifold as water cut rise. The scale control within this field was achieved with squeeze treatment residuals protecting the reservoir through the topside process without the need for additional scale inhibitor injection. A review will be presented on how this field could have been developed if all today's scale control/monitoring technology had been available during the CAPEX phase of field development and how this might have an impact on field economics. The paper will outline the methods used to assess the risk of scale and the associated risk manageability of the problem and review how this risk changes through the life cycle of subsea assists under seawater drive and natural depletion. The process and methods of assessing the risk of scale formation during produced water injection will also be addressed. The scale control technology developments have been driven by these perceived risks. Many of the technologies have already been tested within the North Sea. Furthermore, there are trials planned in the deep water fields of the Gulf of Mexico and West Africa. Introduction Flow assurance is an essential aspect of the economic production of crude. 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 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.