Pressures in the Los Monos- Huamampampa System and their Control in Hydrocarbon Fields’ Occurrence and Size

Abstract

More than 25 TCFE of discovered natural gas in the Southern Subandean are related to the the Huamampama (reservoir)-Los Monos (seal, source rock) system. The Huamampampa Fm is a highly diagenized, lower Devonian sandstone (quartzite) which becomes an efficient reservoir when naturally fractured in anticlinal crests. The Los Monos Fm is an up to 1 km-thick, mainly pelitic package, deposited during the Middle Devonian. Despite its relative lower organic content (< 1% TOC on average), it is thought to have generated almost all the hydrocarbon discovered in the Bolivian-argentinean Subandean belt. The Los Monos Fm is typically highly overpressured, a fact that has been explained as a result of hydrocarbon generation and retention. Pressures in the Huamampampa Fm vary from normal (in equilibrium with surface conditions) to strong overpressures (in equilibrium with the Los Monos pressure). High overpressures in the Huamampampa Fm impose a physical limit to traps charge: when the buoyancy pressure related to the gas cap is added, the resultant pressure can produce seal failure. This limitation adds a further complication to the exploration of this already complex structural play. In this presentation we discuss the distribution and causes of the different Huamampampa pressures and their exploration consequences.

AAPG Datapages/Search and Discovery Article #90326 © 2018 AAPG Latin America & Caribbean Region, Optimizing Exploration and Development in Thrust Belts and Foreland Basins. Santa Cruz de la Sierra, Bolivia, June 6-8, 2018