Offshore Mahogany Field Development to Support Trinidad's LNG Plant
Authors: Lachance D.P. , McCleary N.R. 
Published: October 2008

In the mid-1990's, BP Amoco embarked on an accelerated exploration programme offshore Trinidad, discovering in excess of 10 Tscf gas reserves. This led in part to the building of the first LNG plant in the Caribbean at Point Fortin, Trinidad and Tobago. This single-train plant is owned by a consortium of BP Amoco, British Gas, Enron, Repsol, and The National Gas Company of Trinidad and Tobago. BP Amoco will supply 100% of the 475 MMcsfd feed gas initially from Mahogany field, located 61 miles offshore from the southeastern point of Trinidad.

Since the market and demand profile for the field's gas was defined from the beginning, the design of the offshore facilities, supporting pipelines, and field development was tailored to those needs. Some of the results of these designcriteria were: dedicated gas and liquids pipelines, two platform development for reliability, excess gas pipeline capacity for future expansion, drilling of a front-end loading well after project authorisation, use of twin monobores to maximise platform slot utilisation, and batch drilling and completion of wells prior to the start up of the plant. BP Amoco applied current industry project management practices to design, build, and install the facilities, earning a "Best Practical" recognition from Independent Project Analysis, Inc.

Setting the Stage

BP Amoco has operated in Trinidad and Tobago (Figure 1) since the early 1960's, initially as an oil producer from offshore fields southeast of Trinidad. Gas reservoirs were discovered early in BP Amoco's exploration programmes, but these were of secondary importance to the drive to find and develop oil fields. It was not until the 1980's that BP Amoco began commercial production of its first gas field, Cassia, to supply the island gas market.

From that modest start in 1983 to the early 1990's, gas demand increased slowly to around 500 MMscfd. BP Amoco's share of the gas market was easily managed from the Cassia field and from associated gas from the oil fields. In the early 1990's, BP Amoco began an aggressive plan to delineate old gas discoveries and explore for new gas reserves. Rather than wait for the market to supply the gas demand, the approach was to confirm the gas supply (in the form of proven reserves) and then establish the market (either domestic or export). The gas programme was a tremendous success, with over 10 Tscf of new gas reserves found.

At around the same time, BP Amoco joined in a consortium with British Gas, Cabot LNG Corp, Repsol, and the Natural Gas Company of Trinidad and Tobago to form the Atlantic Liquefied Natural Gas Company of Trinidad and Tobago (ALNG). The aim was to evaluate and implement, if feasible, the construction of the Caribbean's first LNG plant to export gas from Trinidad.

The combination of market need (from Cabot and Enagas) and gas supply (BP Amoco's reserve base) quickly advanced the project to actual implementation. The single-train LNG plant is being constructed at Pt. Fortin on the west coast of Trinidad, with planned commercial startup scheduled in the latter half of 1999. In addition, because of the still large proven and probable gas reserve base for Trinidad, the plant was built with expansion (to multiple trains) in mind.

BP Amoco committed to supplying 100% of the feed gas to ALNG's train 1: three million tonnes of LNG per year for twenty years. This correlates to a feedstock gas stream of 475MMscfd.

LNG Upstream Development Project

In early 1995, BP Amoco formed a project team to plan, design, and implement the field development work to supply the LNG feed gas. This team was given sole responsibility for the project and was formed of BP Amoco employees, project manageme