Coal as a Source Rock for Hydrocarbons in Carbonaceous Formations in Venezuela: A Review

Santiago Mesa, Krisbel A.¹; Perez Castellanos, Fabiola Alexandra; Cepeda Andara, Maria de los Angeles; and Mousalli Diaz, Victoria Eugenia
¹[email protected]

The geological debate about whether and to what extent the coals originate hydrocarbons will continue for a long time, however, worldwide there have been several papers that provide insight into the organic components of the coal and the role they play in the origin of hydrocarbons.

The West of Venezuela is represented by the following carbonaceous formations: Marcelina, Los Cuervos, Carbonera and Cerro Pelado and the East is represented by the following carbonaceous formations: Naricual and Quebradón, all of Tertiary age. Considering the oil between the window range Ro = 0.5 to 0.6% to 1.3-1.35%; the formations: Marcelina, Los cuervos, Carbonera, Naricual, Quebradón and Cerro Pelado present values of Ro within the lower generation window, indicating that these formations could be generating hydrocarbons. Another parameter that reaffirms this condition is the Tmax, which indicates that the formations: Marcelina, Los Cuervos, Carbonera, Cerro Pelado and Naricual are mature rocks while the Quebradón Formation has a Tmax that Blandon, (2006) classifies in immature; however, the value of Tmax value is very close to maturity and due to high organic matter content of these formations, they require less temperature to mature and therefore they can be considered as generating rock in the same way as the other rocks. The carbonaceous formation with the highest rate of hydrogen is the Cerro Pelado Formation with potential for oil and the formations: Marcelina, Los Cuervos, Carbonera, Quebradón and Naricual and could be considered oil and gas generators.

The La Luna Formation and Querecual Formation are widely recognized as the main source rocks in Venezuela. The source rocks have TOC values, classified in excellent source rocks, comparing these values with those carbonaceous formations can be seen at a glance that the COT of these formations are remarkably high compared to having the rocks COT sources, these high values are due to the fact that carbonaceous rocks have more than 50% organic matter, contrary to the sources rocks, which consist mainly of clastic materials and to a lesser extent, by organic matter. The thermal maturity, calculated from the Tmax in the La Luna Formation and Querecual Formation, show that these are overripe rocks compared with carbonaceous formations that are classified by its Tmax as mature rocks, indicating that these carbonaceous formations are within the oil generation window.

AAPG Search and Discovery Article #90166©2013 AAPG International Conference & Exhibition, Cartagena, Colombia, 8-11 September 2013