Development planning of deepwater gas fields: the application of floating production platforms

Abstract

Producing North West Australia (NWA) deepwater hydrocarbon reserves, particularly gas reserves to LNG plants, poses unique challenges. These include extreme metocean conditions, unique geotechnical conditions, long distances to infrastructure and LNG plants, as well as high reliability/availability of supply. This extended abstract addresses important technical, commercial and regulatory factors that drive the field development planning, including the selection of suitable production facilities for these deepwater hydrocarbon developments off NWA. While all-subsea developments have been an inspiration for offshore engineers for a few decades, subsea gas compression, dehydration, power supply and control are still technically and commercially demanding, especially for long distance tie-backs. Subsea well intervention and facility maintenance requirements also favour the application of dedicated floating platforms. A wet or dry-tree floating production platform, therefore, is required in most cases. Whereas Semisubmersible, TLP, Spar, FPSO and FLNG (or LNG FPSO) designs all have the attributes to be a host gas production facility or a part of a production system, only oil FPSOs have been installed in this region to date. Linkages between key reservoir and fluid characteristics and surface facility functionalities are discussed in this extended abstract. Advantages and disadvantages of various platform designs are compared. A focus is on the influence of regional drivers and site characteristics, in particular, metocean and geotechnical conditions and remoteness of the NWA fields. The differentiation between oil and gas developments are addressed. It is emphasised that platform applicability and compatibility should be assessed in the context of field development planning for individual projects to achieve optimum risked life cycle financial values.