Case History of Oil Well Performance Monitoring and Production Optimization in the Eldfisk and Ekofisk Fields, Norwegian North Sea
Abstract: fax 01-972-952-9435. AbstractThis case history reviews the systematic well performance monitoring procedures developed and implemented for the Eldfisk and Ekofisk Fields in the Norwegian North Sea. Examples of production optimization projects implemented as a result of the performance monitoring system are presented. Changes in well performance due to acid washes, acid fracture restimulations, perforation additions and tubing changeouts are illustrated in the examples presented.
Search citation statements
Paper Sections
Citation Types
Year Published
Publication Types
Relationship
Authors
Journals
Cited by 4 publications
References 20 publications
As part of the long tradition of innovative production growth and enhancement projects in the Greater Ekofisk Area, in 2004 ConocoPhillips Norway AS (COPNo) implemented the Onshore Operations Centre (OOC). The OOC facilitates improved collaborative working processes that optimise production and streamline operations through more proactive use of both field equipment and software tools. This paper describes the specification, development and implementation of the online production optimisation software used in this project. This software was provided and developed by EPS Ltd, a Weatherford company, in collaboration with COPNo. Specification of the system started in 2005, based on years of prior experience with network production modelling tools in the Ekofisk area, to simulate and optimise production from the reservoir to the export meter. The system is designed to fully utilise the OOC's continuous measurement and recording systems, throughout the entire production and process network. This production optimisation system aims to complement the existing informational displays and charts by the calibration and optimisation of complete network models several times a day. The optimisation results and comparison with real-time data and operating objectives are made available to users through a web interface so that they can be used by the operator and partner company staff at any location. Models of the wells and production/process network have been developed, following extensive discussions with all relevant disciplines, to ensure that these models can resolve the regular questions faced by the Greater Ekofisk operations teams. In addition to the daily simulation and optimisation scenarios run by the full, online system, the constituent parts of the full model can be also run offline to help evaluate exceptional production issues. The operator is experiencing benefits in two main categories firstly by identification of production problems with wells or plant that prevent the system from achieving target production and secondly by having continuously updated production scenarios available on which planning decisions can be based. These results will be discussed, with many examples. Introduction The Ekofisk field is located in the Southern North Sea in Norwegian production license PL018, operated by ConocoPhillips and was discovered in 1969. The ConocoPhillips Group includes Total E&P Norge, Eni Norge, StatoilHydro and Petoro and operates several other fields within this license including Eldfisk, Embla and Tor. Current production from the 150 natural flow and gas-lifted development wells in these fields is over 300,000 barrels of oil with over 300 MMSCF/D of associated gas. The Ekofisk field and the Eldfisk field are also currently being waterflooded (Hermansen 2002) with a total injection rate of approximately 600,000 barrels of water per day. Production from the license block fields is commingled and processed on a centrally located facility, Ekofisk J, and products exported to the market through an oil pipeline to Teeside, UK and a gas pipeline to Emden, Germany. The production network modelled in this project, including the main facility and pipeline system, is shown in figure 1. The Ekofisk A, B, C, M, X, Eldfisk A, B, Tor and Embla jackets all support production wells with limited separation facilities. The other jackets support compressor and process facilities.
As part of the long tradition of innovative production growth and enhancement projects in the Greater Ekofisk Area, in 2004 ConocoPhillips Norway AS (COPNo) implemented the Onshore Operations Centre (OOC). The OOC facilitates improved collaborative working processes that optimise production and streamline operations through more proactive use of both field equipment and software tools. This paper describes the specification, development and implementation of the online production optimisation software used in this project. This software was provided and developed by EPS Ltd, a Weatherford company, in collaboration with COPNo. Specification of the system started in 2005, based on years of prior experience with network production modelling tools in the Ekofisk area, to simulate and optimise production from the reservoir to the export meter. The system is designed to fully utilise the OOC's continuous measurement and recording systems, throughout the entire production and process network. This production optimisation system aims to complement the existing informational displays and charts by the calibration and optimisation of complete network models several times a day. The optimisation results and comparison with real-time data and operating objectives are made available to users through a web interface so that they can be used by the operator and partner company staff at any location. Models of the wells and production/process network have been developed, following extensive discussions with all relevant disciplines, to ensure that these models can resolve the regular questions faced by the Greater Ekofisk operations teams. In addition to the daily simulation and optimisation scenarios run by the full, online system, the constituent parts of the full model can be also run offline to help evaluate exceptional production issues. The operator is experiencing benefits in two main categories firstly by identification of production problems with wells or plant that prevent the system from achieving target production and secondly by having continuously updated production scenarios available on which planning decisions can be based. These results will be discussed, with many examples. Introduction The Ekofisk field is located in the Southern North Sea in Norwegian production license PL018, operated by ConocoPhillips and was discovered in 1969. The ConocoPhillips Group includes Total E&P Norge, Eni Norge, StatoilHydro and Petoro and operates several other fields within this license including Eldfisk, Embla and Tor. Current production from the 150 natural flow and gas-lifted development wells in these fields is over 300,000 barrels of oil with over 300 MMSCF/D of associated gas. The Ekofisk field and the Eldfisk field are also currently being waterflooded (Hermansen 2002) with a total injection rate of approximately 600,000 barrels of water per day. Production from the license block fields is commingled and processed on a centrally located facility, Ekofisk J, and products exported to the market through an oil pipeline to Teeside, UK and a gas pipeline to Emden, Germany. The production network modelled in this project, including the main facility and pipeline system, is shown in figure 1. The Ekofisk A, B, C, M, X, Eldfisk A, B, Tor and Embla jackets all support production wells with limited separation facilities. The other jackets support compressor and process facilities.
fax 01-972-952-9435. AbstractThis paper illustrates how pressure data acquired from permanent downhole gauges in a shallow water offshore field are analyzed to provide insight into well performance and reservoir monitoring required for key business decisions. A continuous productivity index is generated to analyze the progressive well performance. Near wellbore damage or water influx into the wellbore in the case of unfavourable mobility ratio is easily flagged off. Combination of productivity index, bottomhole flowing pressure and production data provide robust analysis of the well performance based on which quicker decisions can be made on whether a remedial intervention is required or not. Where the right remedial interventions are made, for example when no stimulation is carried out because variation in productivity index is due to increasing water influx and not near wellbore damage, the derivable benefits are sustained oil or gas production, optimisation of recovery, reduction of operational expenditure, all leading to maximised life cycle economics for the well.
The Eldfisk oil field is a high porosity, low permeability reservoir of soft chalk in the Norwegian North Sea. Commercial oil production from the Eldfisk field is dependent on well stimulations involving hydraulic fractures. To date, pseudo limited entry (PLE) acid fracturing has been the standard completion technique that initiates relatively high (5000 bopd) individual well oil production rates. Over time however, many of the Eldfisk wells have experienced rapidly declining oil production. The main causes of the decreased well productivity are attributed to hydraulic fracture closure, solids production and casing collapse. Initial calculated skin values of -4.5 on average increase annually at a rate of +0.6. Through year 1999 over 100 casing deformations have been logged in the reservoir. The root problem behind the productivity deteriorations is the Eldfisk field soft chalk nature where the Brinell Hardness Number (BHN) is commonly less than 5 for the most productive zones. In late 1997, an alternative completion technique involving four hydraulic propped fractures was successfully executed in a horizontal well. Evaluation of rate-time flow efficiency for the propped fractured well versus acid fractured wells with the use of an analytical model is reported in this paper. In addition, the analytical model is used to run predictions of increased multiple propped fractures. This paper relates formation BHN to the hydraulic fracture design criteria and concludes that productivity for hydraulic propped fractured wells in soft chalk formations is preserved over time to a greater extent versus the current standard PLE acid fracture technique. This paper concludes that an additional horizontal well with eight hydraulic propped fractured zones is warranted to improve understanding of the cost effectiveness of this alternative oil recovery completion technique for the Eldfisk chalk field. Introduction Since the early 1970's, petroleum engineers working on North Sea chalk fields have been challenged to design well stimulation treatments focused on hydraulic fracturing of the low permeability, fragile chalk formations all the while with an eye on costs. Fracturing is necessary to make the low permeability chalk formations produce economically. Conventional acid fracturing has been tried on all of the chalk fields. Both field experience and research (Ref. 1) have shown that acid fracturing render attractive near term oil production, however, for some of the chalk fields, the medium term production period is poor. The fall off in production is attributed to low hardness and homogeneous nature of the chalk whereby the etched surfaces of the hydraulic acid fractures close with increasing stress. To date, there has been oil production from over ten chalk fields in the North Sea. It would be convenient if one standard well completion would serve all the fields, however each individual North Sea chalk field has its own unique static and dynamic rock parameters that dictate optimum completion design. Geographically, starting with the southern North Sea Danish chalk fields, after initially stimulating with acid fracture treatments, there have been over 100 propped fracture treatments placed in horizontal wells in the Dan field (Ref. 2). Offset to the Dan field is the Gorm field, which has also utilized hydraulic propped fractures in some its water injection wells (Ref. 3). Further north, still in Danish waters, the South Arne chalk field development strategy has focused on the drilling of horizontal wells with completions involving multiple propped fractures (Ref. 4). The advent of propped fractures in Norwegian chalk reservoirs was first introduced at the Valhall field (Ref. 5). The evolution from exclusive use of acid fracturing to propped fractures for all of the above mentioned fields has centered on one mutual goal, namely productivity preservation.
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.
Contact Info
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Product
Resources
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.
