PETROGRAPHY AND BIOSTRATIGRAPHY OF #101 LAS CANAS & MESITA #1 CORES, GOLDEN LANE/POZA RICA TREND, MEXICO

In 1916 giant oil fields were discovered in the Golden Lane (Faja del Oro) and Poza Rica areas of the Tuxpan Platform, Mexico. Fields in the Golden Lane constituted the principal source of hydrocarbons for the republic of Mexico during its early development. Pemex/Shell released two cores from two Golden Lane fields (Cañas and Mesa Cerrada) to the author in the fall of 2003. This Abstract summarizes the petrography of 129 thin sections cut from these unique cores. In 1956, the Cañas Field was discovered southwest of Tuxpan, Veracruz. Reefal El Abra limestones (Albian) in this Field produced 21° API gravity oil from an average depth of 828 m. Thin sections cut from conventional cores (1-4, 6-7, 9-11, 13-17) in the #101 Cañas well, reveal the following downhole trends (873-2979 m): miliolid foraminiferal mudstone with moldic porosity (C1); influx of quartz (C2); chert overlain by organic-rich foraminiferal mudstone grading to rudist, vitrinite-rich foraminiferal mudstone (C3); brecciated oil-stained rudist wackestone with Dictyoconus walnutensis (Lower Cretaceous-Albian) and Cuneolina sp. (C4). C6 contains D. walnutensis, Cuneolina sp. and Barkerina barkerensis (Albian) as well as rudist boundstones. C7 continues this trend. C9 and C10 contain similar fossils in addition to bryozoa, and spectacular rudists. C11 displays a pelletoidal facies along with stylolitic, rudist boundstones. C13 is similar. C14 is oolitic/oncolitic and has oil stains along stylolites. An influx of quartz begins in C15, and abundant rudists dominate the lower portion of C15. Lithic arenites with hematite cement occur in C16. The deepest core, C17, displays subarkoses and quartz arenites cemented with hematite. The Mesita #1 well also cored El Abra reefal limestones, and is part of the Mesa Cerrada Field. This Field, also discovered in 1956, has produced 20° API gravity oil from an average depth of 1084 m. Four conventional cores (C2, C3, C4 and C5) were cut from this well. Thin sections from these display the following downhole patterns (1477.0-1923.5 m): Cuneolina mudstones (C2, C3); rudist boundstones with orbitulinid foraminifers (C4); and hexacoral reefal wackestones with D. walnutensis (Late Albian) – C5. The #101 Las Cañas and the Mesita #1 are representative of the giant Pimienta-Tamabra (!) petroleum system which has total reserves of 66.3 BBO and 103.7 TCF of natural gas (83.6BBOE).