Abstract

A technical assessment of options for transporting associated gas produced from deepwater oil developments in the Gulf of Mexico is being completed. The options being considered include gas pipeline; processes such as Liquefied Natural Gas (LNG), Compressed Natural Gas (CNG), and Gas-To-Liquid (GTL) that convert the gas to a another state or product for transport by a vessel to shore; Gas-to-Wire (GTW) or the generation of electricity for transmission to shore by subsea transmission lines; and Gas Reinjection (GR) and subsequent production and transport by one of the previously mentioned options. This paper provides preliminary results from this ongoing study.

Introduction

This technical assessment of gas transportation options is being conducted by the Offshore Technology Research Center (OTRC) for the Minerals Management Service. The Offshore Operators Committee is providing assistance through helping to coordinate industry input and participation in this project.

The MMS plans to use the results of this study to assess gas transportation options that might be proposed for deepwater development projects in the Gulf of Mexico during the next decade. Results could also be useful for studies pertaining to deepwater oil and gas development in the Gulf of Mexico.

It should be noted that the purpose of this assessment study is:

  • To generate consistent or analogous information on the various systems,

  • To treat all systems in a uniform and consistent manner, but

  • Not to attempt to determine which system is "best". "Best" in a project sense will depend on project-specific factors and operator-specific drivers and opportunities - both technical and economic.

Scope.

This technical assessment assumes a deepwater oil development from an FPSO, and considers various alternatives for handling the associated gas illustrated in Figure 1. Gas transportation options that are being studied include export via pipeline (the base case); processes such as LNG, CNG, and GTL that convert the gas to another state or product for export via a vessel; generation of electricity for transmission to shore; and injection and deferred production. FPSO production developments in depths of 6,000 ft to 10,000 ft are being studied with various export destinations for the gas or gas-product as shown in Figure 2. A range of gas rates and distances are considered for each gas handling technology.

Figure 3 schematically illustrates the FPSO with oil processing and gas processing systems. The technical assessment addresses the following aspects of the gas transportation options:

  • Technical, commercial, and regulatory readiness

  • HSE risks and mitigation measures

  • Costs (CAPEX, OPEX)

  • Process efficiency

A previous study [1,2] determined that risks for an FPSO development utilizing shuttle tankers to export oil and a pipeline to export gas were similar to the risks of existing deepwater systems in the Gulf of Mexico (TLP's, spars, platforms serving as a hub/host for deepwater production) that use pipelines to export both the oil and gas. Thus the gas pipeline case is considered to represent a baseline for this study.

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