Oil and gas have been produced off the east coast of Trinidad for over 30 years. Production from the authors? affiliated operations currently originates from eight main fields and is transported between satellite/complex platforms and to onshore terminals through about 50 individual pipelines. Despite excellent service history, the operator recently committed itself to implementing a major work program to clearly demonstrate functional integrity of the main oil and gas lines. This program is a formidable challenge because pigging of pipelines was rarely performed over the years, and in most cases, basic facilities (e.g., pig traps) are lacking.
Following risk-ranking, several pipelines were targeted for initial rehabilitation. However, work was first directed to short infield oil lines to develop the basic facilities design, installation and pigging skills. These trials not only successfully removed huge amounts of sand and scale, but also revealed many pitfalls to be avoided with the main pipelines. Of importance, the effectiveness of various cleaning tools was evaluated, methods to free stuck pigs established and solids handling routines developed. Following a now understood methodology, main oil line pig traps were installed, pipelines were progressively pigged clean and intelligent pig inspected. Unfortunately, little went as planned. Overall outcomes are discussed, as are the numerous problems, solutions, surprises and
successes encountered along the way. The experiences demonstrate that through commitment and hard work,
valuable older pipelines can be functionally reinstated for years of future service.
The Teak, Samaan and Poui oil fields were developed and began producing in the early 1970?s. These fields sit approximately 20-50 kilometers (12.5-30 miles) off the southeast coast of the island of Trinidad. Initial gas production began with the Cassia field in the early 1980?s, followed by Immortelle and Flamboyant in the early 1990?s. Development of additional high deliverability gas finds hastened in the late 1990?s as an onshore liquefied natural gas (LNG) consortium was formed and several LNG process trains were constructed. The end result has been a vast accumulation of offshore assets, pipelines and onshore processing terminals, with current production levels of about 77,000 bbls oil / day and 1.6 billion cubic feet gas / day. Overall layout is shown in Figure 1.
The operator?s pipeline system consists of 50 individual lines. A majority of these are short infield pipelines from satellite to complex platforms, but there at least 15 main transmission lines. Newer pipelines are routinely pigged and inspected, but at least 9 main oil and gas pipelines ranging in age from 10-30 years have never been pigged. Despite these maintenance shortcomings, service leaks have been relatively few. However, corporate Process Safety / Integrity Management (PS/IM) expectations go well beyond leak-free service, such that integrity and fitness-for-service must be deterministically demonstrated. In practice, these expectations require intelligent pigging of the pipelines.
