Some of the most significant recent development in subsea design has been within subsea processing, in particular the removal of produced water from the oil closer to the reservoir and subsequent reinjection of this water. Significant effort is being put into both downhole and seabed based separation and re-injection systems for produced water. This paper addresses seabed based solutions. Although subsea processing has been about for at least the last decade, it is first now (with Troll Pilot) oil companies are gaining enough confidence in the technology to actually consider it a viable field development option. A big question mark is still set on the long-term operational experience. Will the system give satisfactory availability without frequent costly interventions? Major challenges are related to rocess/flow assurance and other operability issues. This paper starts with a brief discussion of these challenges in general and concludes with a typical case (Troll Pilot) where this is discussed in more details. The Troll Pilot case shows how significant effort went into process design of the system in order to minimize the uncertainties and risks associated with this novel subsea processing system. Introduction Until recently the injected water used for reservoir pressure support has normally been seawater. The produced water has been treated and disposed to the sea with resulting pollution from remaining oil and production chemicals. In the last few years the trend has rapidly changed towards using produced water instead of seawater for reservoir pressure support, because of a number of benefits such as: Reduced pollution, less problems with scaling due to seawater and produced water mixing and finally less risk of H2S formation in the reservoir. With increasing focus on the environment, some oil companies even consider to reinjects all produced water into dedicated disposal wells regardless of any improved recovery. Together with the trend towards subsea wells at increasing sea-depths and offsets, it seems obvious that the produced water should be separated from the oil and reinjected close to he subsea wells to avoid long transport distance to and back from the platform. The worlds first system of this kind will be installed this year on the Troll Field. ABB Offshore Systems (ABBOS) is the main contractor for the operator of the field, Norsk Hydro. The system is developed to separate and re-inject the produced water from 4-8 subsea wells. It is called Troll Pilot because an important objective is to get operational experience before it will be considered a standard field development option for future projects. To give subsea separation concepts a chance for future field developments, it is important to design the system for operational flexibility, high availability and minimum need for maintenance. To achieve this ABBOS and ABB Corporate Research have given large focus to process operational aspects both for the more general SUBSIS project (Subsea Separation and Reinjection) and the Troll Pilot project. In this paper Troll Pilot is used as an example to outline some of the main operational challenges and how they can be solved. Main emphasis is on special problems related to Subsea Separation and Reinjection even though some of these may also be relevant for topside systems. Subsea Removal of Produced Water As the offshore industry moves into increasingly deeper and remote waters and there at the same time is an increased focus on low oil prices and environmental impact of oil and gas production, the traditional field development concepts needs to be challenged in order to provide sound field economics. One clear trend in this picture is
Two trends in development and operations of offshore oil and gas installations give increased demand for real-time monitoring and control; number & reach of subsea tie-ins and emerging implementation of integrated operations solutions. Within integrated operations, remote operation and collaboration between onshore and offshore are key elements. Sophisticated monitoring and control applications for wells and pipelines have been available from several vendors for some time. However, these applications have generally been stand-alone expert applications connected to a single subsystem, for example, a slug control solution for pipelines located in the plant control system or a virtual flow metering system for wells located in the subsea (control) system. The usage and benefit of these systems have therefore been limited. This paper outlines how monitoring and control applications for gathering networks should be structured in an integrated operations framework, and which benefits this will give for operators. Structuring of the different applications ensures that data from monitoring applications are easily available for a large group of users while ensuring that closed-loop control applications retains the robustness and security that is required. Furthermore, recent developments of the applications itself, partially made possible by the modern integrated operations system topology with increased data availability, provides additional functionality not only for expert users, but for generalists as well. Finally, synergies between different monitoring and control applications can give additional value to the users. Control and monitoring for remote subsea field in an integrated operations framework offers benefits such as faster decision making processes, increased production, improved deduction testing, condition monitoring of sensors using a combination of virtual metering and process data. The paper outlines the status and future development trends for control and monitoring applications for subsea fields, illustrates the value of the technology and gives recommendations for implementation.
TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractWaterflood injection on the Shell Bonga field offshore Nigeria is accomplished via a network of subsea flowlines and 15 subsea injection wells. Maximizing water injection volume is an important economic objective for Bonga. Water injection is used for maintaining the reservoir pressure and thereby maximize oil production. The water injection flowrate to each well is limited by the fracture pressure of the overlying shale layer. Fracture of overlying shale could significantly reduce oil recovery from the damaged reservoir.Hence, it is important to accurately control the reservoir injection pressure such that volume of injected water is maximized without excessive risk of damaging the overlying shales. Since there are no downhole pressure gauges in the injection wells, the downhole injection pressure must be estimated from other measured variables.For this, we developed a novel technology, WRIPS (Waterflood Reservoir Injection Pressure System). The WRIPS algorithm is used to:Estimate downhole injection pressure based on the model and available measurements Estimate injection pressure uncertainty as a function of available measurements Calculate an injection pressure target as a function of system conditions Calculate injection rates for wells where the venturi has failed Data reconciliation: calculate the most probable pressures and flowrates based on model, measurements, and sensor accuracies Set conditioned alarm flagsThe paper gives a brief description and the experience gained with WRIPS applied to water injection wells. The main contribution from the paper is to demonstrate the benefits with such a system and that the WRIPS is an attractive solution compared to expensive downhole pressure gauges.
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.
customersupport@researchsolutions.com
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.