AAPG ACE 2018

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Determination of Source Rock Kinetic Parameters for Petroleum Systems Modeling of the Mexican Perdido Fold Belt

Abstract

In order to constrain the petroleum system modeling of the Perdido Fold Belt, Gulf of Mexico, kinetic parameters of the potential source rocks in this area were determined using the PhaseKinetics approach. In the Mexican sector this petroleum province has been successfully explored for oil, with a series of light oil and gas discoveries. The intervals documented as potential source rocks in the area correspond to the Oxfordian, Tithonian, Barremian, Turonian and Eocene units.

The lack of immature well samples from these units in the studied area led to the selection of analogous immature well core samples from the nearby onshore Tampico-Misantla Basin, northeast Mexico. Four core samples were analyzed in this study: 1) Oxfordian organic rich argillaceous mudstone; 2) Tithonian (Pimienta Formation), recrystallized organic rich argillaceous mudstone; 3) Tithonian (Pimienta Formation), organic rich silty mudstone partially silicified; and 4) Turonian (Agua Nueva Formation) organic rich wackestone.

All samples show Type II kerogen, with a very good organic richness between 2.61-4.31% total organic carbon (TOC) and high petroleum generating potential from 499 to 631 mg HC/gTOC. Vitrinite reflectance values range from 0.22-0.30%, while Tmax varies from 418-428°C, both indicating that the samples are thermally immature with respect to petroleum generation.

Bulk kinetics were determined using open-system pyrolysis at three different laboratory heating rates (0.7, 2.0 and 5.0 K/min), and compositional kinetics were calculated by closed-system MSSV-pyrolysis at a heating rate of 0.7 K/min up to temperatures representing 10, 30, 50, 70 and 90% transformation. The calculated kinetics of petroleum generation are characterized by relatively narrow activation energy distribution indicating the presence of an overall homogeneous Type II kerogen type in all cases. Bulk activation energy distributions measured in the source rock samples vary as follows: Oxfordian 46-56 kcal/mol, Tithonian 42-58 kcal/mol and Turonian 44-59 kcal/mol.

A paraffinic-naphthenic-aromatic low wax petroleum-type organofacies, typical for a marine depositional environment, was predicted for all samples. The kinetic parameters determined in this study allowed to reduce the uncertainty for the calculation of the organic matter transformation ratio in the petroleum systems modeling of the Mexican Perdido Fold Belt.