Scale deposition poses serious challenges to maintaining production and minimizing operating costs and it ranks high amongst the concerns of operators presenting a major threat to flow assurance, not least for remote subsea and satellite unmanned developments. A new methodology enabling the early detection, type identification, estimation of the thickness of the scale deposit and its rate of accumulation over time is presented using dual-energy spectral gamma ray / venturi multiphase flow meters. Several field examples of scale built-up are presented with detailed analysis showing the sometimes-surprising speed of deposition even at very low water cuts. The data from dualenergy spectral gamma ray / venturi multiphase flow meters was used to define the type of acid treatment required and to evaluate its efficiency. The impact of scale deposition on the metrological performance of the meter is illustrated and the procedures for quantification and compensation for maintaining the measurement quality over time is presented. Introduction Deposition of scale represents a major threat to flow assurance, with particularly serious consequences on subsea developments, and it poses serious challenges to maintaining production and processes optimisation. It can represent a large loss of production and diminish a field's net present value. Tjomsland et al1 quantified the value of scale control in the Veslefrikk field in Norway at U.S. dollars 1.1 billion. Quantification of scale deposition is of primary importance for the determination of remedial / corrective action. In some areas such as Canada and the North Sea, where entire regions are prone to scale, scale is recognized as one of the top production challenges. Many mechanisms can lead to the deposition of scale in the reservoir, in the completion, in surface lines and production process equipment. For example, scale can be generated by the incompatibility between injected seawater and reservoir water. Van Khoi Vu et al2 report that more than 320 g of barium sulphate could potentially be deposited per cubic meter of coproduced water in the Girassol field in Angola. Scale can develop in the formation pores near the wellbore - reducing formation porosity and permeability. It can block flow by clogging perforations or forming a thick lining in production tubing. It can also coat and damage production completion equipment such as safety valves, gas lift mandrels and nipples. Scale also accumulates in surface production equipment, such as well heads, master and wing valves, manifolds, flow lines, water knockouts, and test and production separators. It may clog up control lines and wet legs of instruments, affect the proper operation of automatic control and emergency shut down valves all of which are detrimental to production and increase field maintenance costs. Scale deposition may be somewhat controlled in a number of ways such as: injection of inhibitors, chemical or mechanical removal, by changing the operating conditions - pressure, temperature and the composition of injected water. Some mineral scales can be dissolved and removed by acids, whilst most others cannot. Mitigating scale therefore is a difficult task often involving a combination of the above techniques.
The Pyrenees Development comprises three oil and gas fields: Ravensworth, Crosby and Stickle. The fields are located in production licenses WA-42-L and WA-43-L, offshore Western Australia, in the Exmouth Sub-basin and are operated by BHP Billiton (Fig. 1). Eighteen subsea wells, including 14 horizontal producers, 3 vertical water disposal wells and 1 gas injection well have been constructed to date and additional wells are planned for infill and to develop additional resources. First oil was achieved during February 2010 and production exceeded 50 million barrels in November 2011.The Pyrenees fields are low relief, with oil columns of approximately 40 metres within excellent quality reservoirs of the Barrow Group. The 19° API crude has moderate viscosity, low gas / oil ratio (GOR), and a strong emulsion forming tendency which makes oil/water separation and accurate well test metering difficult. Early in the project design phase it was identified that the complex subsea gathering system and the need to reduce measurement uncertainties would dictate special attention to production measurement.Subsea multiphase flow meters (MPFMs) were specified to meet the challenges of production optimization and allocation while at the same time minimizing production deferral for separator testing. Each oil producer is monitored by a dedicated MPFM. With 14 meters, Pyrenees is among the largest subsea MPFM installations worldwide. This paper describes the process of MPFM qualification and commissioning together with their performance over 2 years in the field. We show how close cooperation between the Operator and MPFM Vendor has enabled quality rate measurements of emulsified production despite large changes in producing gas/oil ratio and water cut.While the primary justification for Pyrenees subsea MPFMs was production allocation and optimization, interpretation of transient water cut and GOR data proved valuable for production and reservoir engineering applications. Examples of proactive reservoir and production management including optimizing drawdown of Inflow Control Device (ICD) equipped wells, optimizing well lineup and gas lift to commingled wells are presented.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.