Intergated Field Development For Effective Scale Control Throughout the Water Cycle in Deep Water Subsea Fields

Abstract

Abstract Scale control in produced fluids as water follows the cycle of injection, production, processing and reinjection in oil production facilities is, in many cases, critical to the effective production of hydrocarbons in a safe, economic and environmentally acceptable manner. This paper focuses on the challenges to scale control in deepwater reservoirs, and describes the scale control measures that are designed into the field development plan based on the integration of reservoir simulation, completion design technology and production chemistry.Emphasis is placed on the need to consider the full life cycle of the field, considering a range of development scenarios, such as water flooding with seawater, desulphated seawater, produced water re-injection, aquifer water injection and primary depletion. Advanced fluid flow and reaction calculations that account for in situ scaling reactions and the impact on the produced brine chemistry are used to provide data to refine the economic models used to identify the optimum scale management technologies.The various functions that must be carried out for effective scale management at the CAPEX and OPEX phase are outlined. The paper clearly demonstrates how, by using an integrated team that includes personnel drawn from operating company, chemical service company and research institute backgrounds, a multi-disciplinary approach may be used to integrate engineering and chemical solutions to effectively arrive at the most economic scale control programme for these challenging fields. Introduction After a brief overview of the causes of oilfield scale, where it forms and how it may be managed throughout the life cycle, this paper discusses the impact that a variety of production related disciplines, including reservoir engineering, completion engineering, production chemistry and operations have on the management of scale. Oilfield Scale Oilfield scales are inorganic crystalline deposits that form as a result of the precipitation of solids from brines present in the reservoir and production flow system.The precipitation of these solids occurs as the result of changes in the ionic composition, pH, pressure and temperature of the brine.There are a wide range of such solids which can interfere with the effective recovery of hydrocarbons, Table 1.There are three principal mechanisms by which scales form in both offshore and onshore oilfield systems: 1) Decrease in pressure and/or increase in temperature of a brine, leading to a reduction in the solubility of the salt (most commonly these lead to precipitation of carbonate scales, such as calcium carbonate); (Equation 1) 2) Mixing of two incompatible fluids (most commonly formation water rich in cations such as barium, calcium and/or strontium, mixing with sulphate rich seawater, leading to the precipitation of sulphate scales, such as BaSO[4]); (Equation 2) Other fluid incompatibilities include sulphide scale where hydrogen sulphide gas mixes with iron, zinc or lead rich formation waters (equation 3); (Equation 3)