Cantarell's Akal C Complex: the World's Largest Offshore Gas Treating and Lift Gas Generation Platforms

Abstract

Abstract Petróleos Mexicanos (Pemex) is undertaking a major upgrade and expansion of the Cantarell oil field in the Gulf of Mexico in order to increase crude oil production, reduce gas flaring, and improve the reliability and operational safety of existing facilities. Within the Cantarell Field, Akal C is the most important complex due to its gas treating and compression capacities. This paper outlines the design and construction challenges associated with the modernization and expansion of the Akal C complex to meet the Cantarell project objectives. Introduction to Cantarell Oil Field The Cantarell field, located about 80 kilometers (km) offshore of the Yucatan Peninsula in the Bay of Campeche, Mexico (see Figure 1: Location of Cantarell Oil Field), is the largest oil field in Mexico. The Cantarell field is composed of four major fields: Akal, Nohoch, Chac, and Kutz, in addition to the reserves in the newly discovered deeper Sihil Field. Cantarell's largest reservoir, the Akal field, is considered the sixth largest reservoir in the world. Since Cantarell's initial discovery in 1976 and exploitation in 1979, reservoir pressure has declined by more than 60 percent (see Figure 2: Reservoir Pressure and Oil Production Over Time), leading to numerous operational difficulties in sustaining the target oil production rate, including falling well fluid levels and the increased need for lift gas. In addition to overcoming the impacts from falling reservoir pressure, Pemex wanted to accomplish several key objectives:increase the reserves,more than double oil production,utilize all the produced gas by adding sufficient compression and process capacity, andmodernize the existing facilities to improve operational safety and efficiency. The program to do so has resulted in several major concurrent, integrated projects of unprecedented size and complexity, which together have created the largest offshore expansion of its type in the world. Major components of the Cantarell project include:modernize 39 existing platforms and constructing 26 new main platforms to increase oil and gas production and handling capacity,developing two new complexes (Akal L and B),building a floating storage/offloading facility for oil production handling,building the largest nitrogen generation plant in the world to supply 1,200 million standard cubic feet per day (mmscf/d) of nitrogen gas to pressurize the oil reservoir,laying more than 400 km of subsea pipelines to augment the existing 1,700 km network,increasing gas handling capacity,building offshore gas treating platforms to generate lift gas,modernizing Akal C to increase its gas compression and processing facilities to generate lift gas offshore, andmodernizing the safety and control systems of all existing platforms and complexes. To execute this massive program, projects were grouped in two "plans," with considerable integration and tie-in between the two. The Short-Term Plan focused on the most urgent upgrades of existing 20-year-old facilities (complexes Akal C, Akal-J, and Nohoch-A) and a new lift gas generation facility at Akal C to allow oil production to increase and allow gas flaring to decrease.