Producing and delivering North West Australia (NWA) deepwater gas reserves to LNG plants poses unique challenges. These include extreme metocean conditions, unique geotechnical conditions, long distances to infrastructure and high reliability/availability requirement of supply for LNG plants. A wet or dry tree local floating host platform will be required in most cases. Whereas semisubmersible, TLP, Spar and floating LNG (FLNG) platform designs all have the attributes to be a host facility, none has been installed in this region to date.
This paper will address important technical, commercial and regulatory factors that drive the selection of a suitable floating host platform to develop these deepwater gas fields off NWA. Linkages between key reservoir and fluid characteristics and surface facility requirements will be established. A focus will be on the unique influence of regional drivers and site characteristics including metocean and geotechnical conditions, water depths and remoteness of these fields.
There have been 17 FPSOs producing oil in Australian waters. These facilities have been chosen because of the remoteness of the fields and the lack of pipeline and process infrastructure. Storing oil on the FPSO for offloading and shipping from the fields becomes an obvious solution. Semisubmersible, TLP or Spar platforms show little advantage in such developments.
For deepwater gas developments, the product has to be processed, compressed and piped to shore for liquefaction. As host processing facilities, Semisubmersible, TLP and Spar platforms have clear advantages over FPSOs because of their superior motion performance in the harsh Australian metocean environment and other benefits such as facilitating drilling, dry tree completion and well services. FPSOs or FSOs may be applied for storage of associated oil and condensates. For marginal and remote gas field developments, an LNG FPSO (FLNG) may be an attractive option as it eliminates long pipelines and land-based liquefaction plants.
As discussed by Dorgant and Stingl (2005), a deepwater field development life cycle following discovery usually involves five distinct phases, Figure 1. The "select?? phase occurs after a discovery has been appraised sufficiently to further evaluate it for development. It consists of evaluating multiple development concepts and scenarios and selecting the one that will most likely achieve the identified commercial and strategic goals. Selecting a floating platform and its functions for a deepwater development is an important subset of the select phase and the overall field development planning.
The process of field development planning involves a complex iterative interaction of its key elements (subsurface, drilling and completions, surface facilities) subject to regional and site constraints (D'Souza, 2009). The objective is to select a development plan that satisfies an operator's commercial, risk and strategic requirements. It entails developing a robust and integrated reservoir depletion plan with compatible facility options. The selection occurs while uncertainty in critical variables that determine commercial success (well performance, reserves) is high. One of the challenges is to select a development plan that manages downside reservoir risk (considering the very large capital expense involved) while having the flexibility to capture its upside potential.
This paper presents a methodology for a systematic, robust and conservative ecological risk assessment for estimating environmental consequences and associated risk from ambient air concentrations of atmospheric pollutants and air toxics (also referred to as criteria pollutants and hazardous atmospheric pollutants in the United States legislation respectively), as arising from industrial activities. The paper details the main steps of the risk assessment process and makes a contribution in deriving conservative and safe Reference Concentrations (RfC) such as No Observed Adverse Effect Level (NOAEL) and Lowest Observed Adverse Effect Level (LOAEL) for fauna in their natural habitat, using published scientific dose-response toxicological studies with laboratory animals. It then uses these derived RfCs to determine step changes in consequence levels, from incidental to major, in order to complete the risk assessment. A similar approach is used to assess impacts on the marine environment. This methodology is repeatable and robust and can be applied as a screening level environmental risk assessment to establish conformance to legally postulated levels of acceptable environmental consequences, where available, or acceptable levels of environmental risk, associated with air quality.
Project Background and Setting
The Gorgon Project, operated by Chevron Australia Pty Ltd on behalf of the Gorgon Joint Venture Participants, will develop the Gorgon and Jansz-Io gas-condensate fields, located offshore the north-west corner of Western Australia (WA) (see Figure 1). The approved development will include subsea gathering systems and pipelines delivering the gas to a 15 million tonne per annum (MTPA) liquefied natural gas (LNG) Gas Treatment Plant (GTP) located on the east coast of Barrow Island (BWI), which is a Class A nature reserve, lying some 60 km north of the Australian mainland. The Gorgon Project is an unique LNG Project in that it will also encompass the largest industrial scale acid gas injection undertaking in the world to date whereby some 4.2 MTPA of CO2 and other acid gas components (i.e. residual methane, (CH4), volatile organic compounds (VOCs) and hydrogen sulphide (H2S) removed from the natural gas, will be liquefied and injected via three injection centres in the Dupuy Formation below BWI in the Operations Phase of the Project.
The design team for the Wheatstone offshore platform successfully deployed an ‘Inherently Safe Design' (ISD) approach to engineering the gas processing complex. Through a program of initiatives focused on ISD, a substantial improvement in the safe design of the platform has been delivered.
Major accident events:
The Texas City incident in 2005 initiated the most detailed and far reaching investigation ever undertaken by the US Chemical Safety and Hazard Investigation Board (CSB) at the time. The CSB report included a recommendation that BP form an independent panel to conduct a review of the company's corporate safety culture, safety management systems, and corporate safety oversight at its U.S. refineries. This independent review was conducted and a separate report known as the Baker Report was developed, with the key conclusion being that the process safety culture was deficient.
Major incidents such as the Macondo and Montarra well blow-outs still occur. NOPSA newsletter Issue 86, February 2010 presented data on gas releases, a recognised precursor to major accident events and showed "Design problems at root of most major gas releases??.
In May 2011 Shell announced its commitment to the development of a Floating Liquefied Natural Gas (FLNG) concept by taking the Financial Investment Decision on the Prelude FLNG Project. Prelude is located in Australian offshore waters, approximately 475 km north-northeast of Broome and 825 km west of Darwin, and will be Shell's and possibly the world's first FLNG development. FLNG offers a number of environmental advantages over traditional onshore LNG developments. This paper describes some of these and the associated environmental permitting/approval conditions for the project.
In late 2011 the Queensland State Government of Australia declared the Cooper Creek Basin in South West Queensland to be a Wild River Area under the Wild River Act 2005. The Wild River Area covers a significant proportion of Santos' current tenements and future development interests in the area.
The Wild Rivers Declaration is a highly prescriptive regulatory regime that sets out significant restrictions which would detrimentally impact on existing operations and future oil and gas development opportunities, including emerging coal seam and shale gas prospects in the proposed declaration area. It includes general prohibitions on certain activities across extensive areas of channel country and the imposition of setbacks for activities in proximity to watercourses.
The issue first arose in late 2010 when the Queensland Government indicated its intent to declare the Cooper Creek Basin as a Wild River through its issue of a Declaration Proposal. During the 12 month consultation period that followed, Santos engaged with the Queensland Government regulators and Ministers to assist the Government to make a Wild Rivers Declaration that achieves a balance between protecting the natural values of the Cooper Creek and allowing the continuation of the sustainable development of the petroleum resources within the Cooper and Eromanga Basins.
The paper will provide insight into Santos' experience in taking a lead role in responding to the significant new legislative regime proposed by Government. Key insights include the need for industry tobe proactive and take a role in educating the Government on the industry's operations andthe changes required to ensure compliance with the new regulatory requirements. It will also discuss broadlythe challenges associated with the changing regulatory environment including the role that politics can play and observes that we should continue to expect a ‘Wild' ride whenparticipating in thelegislative developmentprocess.
The significance of the Declaration is that the restrictions for petroleum activities imposed in the Cooper Creek Basin Wild Rivers Declaration may be imposed upon all Wild Rivers areas in Queensland. In addition, other Australian state governments are watching the implementation of Wild Rivers' legislation in Queensland and are considering the need for similar regulatory regimes in their jurisdictions.
As part of the Devil Creek Development Project, Apache successfully used horizontal directional drilling (HDD) with a delayed break out as the installation method for the shoreline crossing of a new gas pipeline at Gnoorea Point, 45 km southwest of Dampier, Western Australia to achieve excellent environmental and social outcomes.
Technical, environmental and community engagement challenges included an HDD reach distance of 1.85 km, a delayed break out technique, hard complex and variable geological strata, the HDD exit point in shallow water (6 m) and surrounded by benthic habitats consisting of corals, seagrass and macroalgae within a Marine Conservation Reserve, stringent regulatory requirements and the onshore drilling location directly adjacent to a heavily used camping area and a public boat ramp with adjacent beach.
To achieve minimal disturbance to the marine environment and social amenity of the surroundings, an extensive and innovative marine monitoring programme was used in combination with an intensive community engagement programme. The techniques used for this project have application to oil and gas activities involving stringent regulatory requirements, sensitive marine environments and proximity to public amenities.
Results, Observations and Conclusions
Mapping of the drilling fluid showed a small area of the seabed that was affected. Some small, unplanned areas of leakage of drilling fluid onto the seabed were also identified and the leaks remediated: these leakages occupied only a very small area of the seabed. Apache were required to demonstrate that HDD activities resulted in no more than 0.5% loss of seagrass, macroalgae and coral based upon losses predicted from mapping, modeling suspended sediment concentrations in the water column and sedimentation rates on the seabed based on drilling fluid discharge rates and applying conservative coral health threshold criteria to discharge model outputs to predict zones of impact to benthic habitats. An extensive marine monitoring programme, sampling before and after HDD, using high definition video camera to capture photoquadrats conclusively demonstrated that losses were significantly less than predicted and permitted.
Drilling operations were a 24 hour activity and located directly adjacent to a popular camp site and boat ramp. Apache engaged with the community before and during the HDD activity and no complaints were received from the users of the area during operations.
Significance of the Subject Matter
Provides an example of industry's ability to operate successfully in sensitive marine environments and close proximity to communities.