The Goliat field will be the first offshore oil field in the Barents Sea and the world’s northernmost offshore oil field. The field is in the southwestern part of the Barents Sea, close to the coastline in an environmentally sensitive area. The implementation of the Goliat oil spill preparedness plan will introduce new technologies and methods, the results of projects and initiatives developed in cooperation with the Norwegian Clean Seas Association for Operating Companies (NOFO). This will give an increased oil spill response capability, especially for the coastal zone.
Goliat Field Development
The Goliat field is an oil and gas discovery in the southwestern Barents Sea. Goliat contains two main oil-bearing reservoirs (Realgrunnen and Kobbe) with 28×106 std m3 of recoverable oil reserves. In addition, the field contains 8.8×109 std m3 of gas. The field is approximately 85 km from the city of Hammerfest in the county of Finnmark and approximately 50 km southeast of the Snøhvit offshore gas field (Fig. 1). The water depth in the license area is between 248 and 436 m.
The Goliat field is to be developed by 22 subsea wells drilled from eight templates linked to a circular floating production, storage, and offloading (FPSO) facility (Fig. 2).
The Goliat development represents one of the largest industrial projects ever undertaken in northern Norway. The well stream will be processed on the FPSO, and the oil will be exported to market using tankers. During the first phase, produced gas will be reinjected to provide pressure drive. This will, in addition to the injection of seawater, attain the total pressure drive necessary to achieve optimal production of the resources. The facility will run on power supplied from land combined with an onboard power-generation system.
In 2009, the Norwegian parliament approved the plan for development and operation for the Goliat field, with seven specific conditions that the project needs to fulfill. For the first time in Norway, one of the specific conditions was related to oil spill preparedness: “In the light of the particular challenges in the northern areas and the Goliat field’s proximity to the coast, oil spill contingency strategies must be assigned very high priority. The operator shall carry out a detailed evaluation of the infrastructure within the area of influence of potential polluting emissions and discharges from the Goliat field. The operator shall implement measures designed to consolidate the oil spill contingency strategies in the affected municipalities … .”
Goliat Oil Spill Contingency
The Goliat oil spill contingency requirements are based on environmental risk assessments and oil spill contingency analyses conducted according to prevailing industry guidelines in Norway.
For the Goliat exploration and production drilling, the dimensioning scenario is a surface spill of oil from the Realgrunnen formation, with a weighted discharge rate of 4594 m3/d and weighted duration of 7 days.
The oil spill contingency in Norway is divided into four consequence-reducing barriers (Fig. 3) in addition to risk-reducing barriers, which are mainly well and process barriers. Norwegian consequence-reducing barriers for an oil spill are
- Barrier 1—Combating oil spills in the open sea close to the source of the discharge
- Barrier 2—Recovery of oil along the drift trajectory of the spill (between the source and the coast)
- Barrier 3—Combat measures in coastal areas and near the shoreline
- Barrier 4—Measures for cleaning the beaches
The barriers in the open sea will be made up by NOFO systems consisting of oil-recovery vessels with tank capacity of 1000–2000 m3, 400 m of heavy offshore boom, and skimmers with capacity of up to 10,000 B/D. The coastal barrier will be based on the use of smaller vessels, including a pool of fishing vessels and equipment suited for coastal waters. On the beaches, the regional intermunicipal contingency organizations will have a key role, assisted by regional, national, and international resources. The Goliat oil spill contingency will also include the capability to use ship-based dispersant systems.
The aim for Goliat oil spill preparedness is to be robust, effective, and well adapted to local conditions. The aim will be realized through the following three specific initiatives new to Norwegian oil fields, in addition to other initiatives:
- Integrated field oil spill detection and surveillance system
- Permanent use of fishing vessels
- Special acute-phase task force
Integrated Field Oil Spill Detection and Surveillance System (All Barriers)
For a number of years, Norwegian authorities have focused on early detection and monitoring of acute pollution. Goliat has focused on this issue since the field was identified, and leak detection has been included in the scope of work for the different Goliat development contracts (subsea production system, flowline and riser, FPSO, and offloading). The Goliat development project has developed an oil spill monitoring strategy that focuses on early detection and reduction of the consequence of any possible leakage or accidental discharge to sea.
Overall requirements on the basis of this strategy are
- Inspection routines shall be established (e.g., for the subsea templates, the flowlines and risers, the electrical cable, and other systems not subject to continuous monitoring).
- Any significant spill on the sea surface shall be detected within 1 hour.
- The automated spill-detection system must be clear and understandable, and data collected through the monitoring system must be available, interpreted, coordinated, and communicated to ensure immediate response.
- Data fusion from multiple sensor systems shall be implemented for detection (e.g., template sensors, radar, and infrared sensors), enabling robust detection.
- Personnel must be trained to assess monitoring data, enabling efficient detection and accurate classification of oil spills.
The detection and monitoring sensors for the Goliat field during production will consist of more than 100 dedicated sensors located on different sensor platforms (templates, risers, FPSO, safety standby vessel, supply vessels, helicopters, planes, and satellites) relevant for Goliat.
On the subsea templates, there will be two independent sensor systems consisting of three acoustic sensors and four capacitance sensors on each of the eight templates. The field internal pipelines will not have any external sensors, but the safety standby vessel will have a remotely operated observation vehicle that, among other tasks, will inspect the field internal pipelines at regular intervals. The Goliat risers will be equipped with sensors that can detect inflow of hydrocarbons into the annulus.
The Goliat FPSO, safety standby vessel, and supply vessels will be equipped with oil-detecting radar and nitrogen-cooled infrared cameras that can be used to detect, measure relative thickness of, and track oil on the sea surface. The vessels will also be equipped with automatic identification system buoys, which can be used to track an oil slick. These sensors will ensure that oil-recovery operations can be conducted during periods with limited light conditions (e.g., polar night) and also will enhance the ability to track an oil slick during periods of good lighting.
In addition to Goliat’s dedicated sensors and sensors on vessels in the NOFO pool, sensors on planes and satellites are available through NOFO agreements.
Permanent Use of Fishing Vessels (Barrier 3)
The use of fishing vessels as part of a coastal oil spill contingency has previously been on an ad hoc basis by the oil and gas industry in Norway. A project was initiated to establish a permanent pool of fishing vessels that can be used by Goliat and other oil and gas activities in the area in case of an oil spill. The project consisted of the following four main goals:
- Change the Norwegian maritime regulations so that fishing vessels could legally be used in oil-spill contingency operations.
- Develop an operational concept for the pool of fishing vessels.
- Develop and acquire dedicated booms, skimmers, and other relevant equipment suitable for fishing vessels.
- Enter into contract with approximately 30 fishing vessels from the Goliat area.
The fishing vessel concept includes fishing vessels, light and medium-sized booms (primarily one-vessel high-speed boom systems) and skimmers, external storage units for recovered oil emulsion, and a larger support vessel. The high-speed boom systems use a paravane to enable one vessel to maneuver and control the boom. The resources are to be organized as one tactical unit supported by a larger support vessel. The concept gives a flexible organizational capacity to handle scattered oil slicks, which can be expected in the coastal areas (Fig. 4).
To secure the availability of the required number of suitable fishing vessels with qualified crew in the case of an oil spill, it was decided that NOFO should enter into contract with approximately 30 fishing vessels. The contract specifies response time and competence requirements and the number of exercises the vessels need to participate in during a year. The fishing vessel pool will use dedicated equipment.
Acute Phase Task Force (Barrier 4)
Traditionally, this barrier has been organized with one-sided focus on beach cleaning after the acute phase is over. Experience from oil spill response operations in Norway and all over the world indicates a need for a higher level of readiness for the acute phase of Barrier 4 (e.g., when oil hits the shore and often congregates in bays and coves). Effective control of this phase will reduce the damage to the environment, preventing penetration of oil into the soil, preventing remobilization of oil, and reducing the extent of future beach cleaning. When the oil reaches the beach, it will often be combated effectively by mechanical means, either from land or sea. Even in bad weather, the oil can be combated in sheltered bays and coves or on the lee sides. Normally, the emulsion will still be relatively mobile and relatively easy to recover with pumps and skimmers.
As part of Barrier 4, NOFO has established a special acute-phase task force, with dedicated personnel and equipment. The group consists of 40 people recruited from Finnmark County and is set up with dedicated equipment. The response time for the group is set to 48 hours, identical to the shortest drift time before oil emulsion reaches the coastal zone from a major oil spill from the Goliat field. If necessary, the task force can be mobilized along the entire Norwegian coastline.
Operations in the acute phase on the beach include
- Acquiring information about, and effecting movement to, locations with free-floating stranded oil
- Locking the free-floating oil with light booms
- Flushing of oil on the shoreline out to sea
- Recovery of free-floating oil with skimmers/pumps
- Locking of any residual oil to prevent remobilization
- Application of sorbents on the residual oil
- Relocation to new position
The goal is that the acute-phase task force should be able to operate as an autonomous unit without significant replenishment for approximately 48 hours. The reason for this is to ensure that the acute-phase task force has the endurance to take action on an independent basis until additional resources and supplies can be mobilized and put in place.
This article, written by Editorial Manager Adam Wilson, contains highlights of paper SPE 156773, “Implementation of the Oil Spill Preparedness for the Goliat Offshore Oilfield Development—The First Oilfield Development in the Barents Sea,” by Erik Bjørnbom and Ole Hansen, Eni Norge; Frode Engen, Statoil; and Sjur W. Knudsen, Norwegian Clean Seas Association for Operating Companies, prepared for the 2012 SPE/APPEA International Conference on Health, Safety, and Environment in Oil and Gas Exploration and Production, Perth, Australia, 11–13 September. The paper has not been peer reviewed.