G. Eric Michael¹, Christof Keuser², Bjorn Wygrala², Dave Hanley¹, David Miller¹, Patrick O'Connell¹
(1) Conoco Inc, Houston, TX
(2) Integrated Exploration Systems, Juelich, Germany

Abstract: 3D Petroleum System Modeling: A new tool in an old exploration area - Webb and Zapata County, South Texas, USA

A hybrid 3D petroleum systems simulator that integrates 3D full physics with fast flowpath modeling is used to calculate reservoir temperature and thermal maturity for a suite of possible sources and reservoirs in the S. Texas area. Pressures in late Paleocene sands of the Lobo trend are compared to those calculated from compaction disequilibrium. Sensitivities to the thermal effects of salt movements and erosion are examined, as well as the possible effects of fault conduits on petroleum migration. Petroleum migration is modeled as an n-component, 3-phase transport process in order to examine possible oil to gas cracking and exploration potential for potential deeper Cretaceous reservoirs.

The late Paleocene Lobo trend sands in Webb and Zapata County are prolific gas producers. They range from mild to hard overpressure (0.55 to 0.8 psi/ft.), and have variable production capacity and quality. 3D maturity and migration modeling combined with geochemical data (e.g. gas stable carbon isotopes) is used to investigate how these Eocene sands were charged, pressured and maintain pressure. Possible theories tested are in-situ charge from adjacent Paleocene/Eocene shales (2 wt.% organic carbon) or external charge from deeper currently gas window thermal maturity Cretaceous and Jurassic source rocks.

Thermal modeling challenge in the study is proper incorporation of significant radiogenic heat production from litharenitic Frio and Wilcox sands and mudrocks. The proper estimation of erosion amount from Laramide uplift across the area is also an uncertainty.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana