Re-Engineering Tank Farms
Authors: Rodriguez Wilfredo A. , Colina Jhonny , Montero Leonardo , Di Matteo Carlos 
Published: December 2007

Foreseeing future operational problems to deal with expected production increase from the Venezuela's Apertura process in Maracaibo Lake, Lagoven's Operational and Technical Management conducted a re-engineering study at the two main tank farms (Ule and Lagunillas) in the Western Division, as part of the strategic plan designed to optimize operating costs and to improve overall efficiency. This paper resumes the process scenario analysis technique applied in optimizing the treating, storing, pumping and transporting processes in these tank farms; which resulted in the identification of new opportunities for improvements with total operating costs savings of 6.1 million dollars per year and reducing capital investments in 16.0 million dollars for meeting future production requirements in the next three years.

Introduction

Lagoven's Western Division actual production of condensates, heavy, medium and light oils from Maracaibo Lake is expected to increase above 1,200 thousand barrels per day by the end of the year 2003, according to the company's future ten-year business plan. All this production is gathered in different flow stations located at the lake and pumped for dehydration and water handling at the two main tank farms located at the Bolivar Coast (Maracaibo Lake's eastern shore): Ule and Lagunillas. See Figure No. 1.

These tank farms have been operated for more than half a century using traditional techniques in the oil field in treating, storing, pumping and transporting the crude oils segregations. To meet future requirements, preliminary studies showed the need of implementing an aggressive capital investment plan in order to update process schemes.

In treating the crude oils, the use of 80–150 thousand barrels wash tanks with operating temperatures between 130 and 150 F and chemical injection is a standard feature at Ule and Lagunillas.

At the Ule Tank Farm, the central gathering point, the incoming main stream (51 percent of the total feed) is medium oils (23–27 API) from the Tia Juana and La Rosa fields; about 23 percent is heavy oils (17–22 API) from the Urdaneta field, along with 26 percent of light oils (31–36 API) from the Center Lake field and condensate (54 API) from the South Lake field. Meanwhile, at the Lagunillas Tank Farm all the incoming stream is heavy oils (14–16 API) from Bachaquero and Lagunillas fields. The current water cuts range between 20 and 35 percent and is expected to increase by 15 percent on future years. Table 1 shows actual and future conditions at these tank farms.

Due to the incremental production, an increase in operating costs from additional chemical consumption (price and volume) and process equipment maintenance was prognosticated. Besides, a great amount in capital investments to procure and install new heaters, pumps, tanks and pipelines was envisioned.

A re-engineering study of all the production system at the Ule and Lagunillas tank farms was carried Out as a result of applying Schoemaker's scenario planning approach (SPA) to evaluate the most critical processes at each tank farm. One of the key issues of the study was directed towards maximum energy recovery from the heating process in the dehydration schemes of the heavy and medium oils.

From the re-engineering studies, a thermal integration concept was defined for the heavy and medium oils dehydration systems at Ule and Lagunillas, by taking advantage of the high temperature (150–180 F) wash tanks' outputs and heat-exchanging it with the incoming field emulsion (85–90 F). This approach showed that the total heat consumption could be diminished by thirty percent.

A new dehydration scheme was defined to allow a 15 percent increase in wash tanks operating temperature (from 130 to 150 F at Ule and from 140 to 180 F at Lagunillas), which would reduce chemicals consumption in as much as 60 percent. P. 687^