Leonardo Manriquez, Abel Moreno,Carlos G. Anaya
Instituto Mexicano del Petroleo
Mexico City
Crude oil assays of three important Mexican export crude oils-Maya, Isthmus, and Olmeca-have been updated.
Most of Mexico's reserves are in the Gulf of Campeche and in the Mesozoic area of the states of Tobasco and Chiapas. Maya is a heavy crude oil of 22 API with high contaminants content, such as sulfur (3.4 wt %) and vanadium (308 ppm).
The Mesozoic area produces crude oils of diverse quality. They are blended to produce Isthmus and Olmeca crudes and to meet the quality of major international export crudes.
Typical recent production volumes of these three important crude oils were: Isthmus, 596,000 b/d; Maya, 1.2 million b/d; and Olmeca, 147,000 b/d.
Total proved reserves of natural gas and crude oil at the end of 1989 in Mexico were 66.4 billion bbl of crude oil equivalent. Of this, 68 vol % was crude oil.'
Isthmus is exported from the Gulf of Mexico ports of Pajaritos, Veracruz, and Dos Bocas, Tobasco, and Cayo Arcas. Isthmus is also exported from the Pacific Coast at Salina Cruz, Oaxaca.
Maya is exported from Pajaritos and Dos Bocas. It will also soon be exported from Salina Cruz.
The largest volume of Olmeca is shipped from Pajaritos. In Mexico, as in the U.S., this crude is used to produce high viscosity index lube oils.
The qualities of Maya, Isthmus, and Olmeca are presented in the following assays and accompanying graphs. Fractions were recovered by true boiling point distillations .2 These analyses update and extend some of the data presented by Hernandez.3
SUMMARIES
Compared to Isthmus and Maya, Olmeca crude is the lightest of the Mexican export. It has fewer contaminants, and its 540 C. TBP distillation produces the largest quantity of distillate. The Olmeca fractions also have the lowest total sulfur content.
The Maya crude is heavy, with an API gravity of 22.2. It has a high contaminant content that induces corrosion in process equipment and causes low running times in thermal cracking units, such as visbreakers and cokers. A proposed refining scheme for the bottom of the Maya barrel consists of atmospheric distillation, vacuum distillation, the Impex process, and visbreaking.4 5
REFERENCES
- Petroleos Mexicano, Memoria de labores de Petroleo Mexicanos, 1989.
- American Society for Testing and Materials, Annual book of ASTM Standards, Petroleum Products, Lubricants, and Fossil, Section 5, vol. 5.01, pp. 567-579, 1985.
- Hernandez, R., "Mexico's export oil: its source and qualities," OGJ, Feb. 19, pp. 89-91, 1979.
- Lopez, R., Cossio, F.A., and Bermudez, O., "Nueva Alternative de Procesamiento de Aceites Crudos Pesados," Revista del Institute Mexicano de Ingenieros Quimicos (IMIQ), vol. 26, Revista IMIQ, 1985.
- Harris, R., "How Mexico Plans to Treat its Heavy Crude," Chemical Engineering, May 28, pp. 20 E-20 F, 1984.
Copyright 1991 Oil & Gas Journal. All Rights Reserved.
