Integrated porosity methods for estimation of gas-in-place in the Muerto Formation of Northwestern Peru

Abstract

The Albian-age Muerto formation in the Talara and Lancones basins of Northwestern Peru is a world-class source rock with high organic carbon (up to 4%, kerogen type III) and thermal maturity for the generation of both oil and gas as constrained by geochemical data presented here. We used wireline logs from one well in the Lancones basin in conjunction with geochemical data to model a multi-porosity model for the Muerto shaly carbonates. Our porosity model suggests total porosity 10.8% (from neutron and density logs), matrix porosity 10.3% (from the sonic log) of which inorganic porosity is 7.96% and kerogen (organic) porosity is 2.02%. Fracture porosity was found to be negligible (0.5%). The study thus incorporates porosities storing both free and adsorbed gas in this self-sourced reservoir. Moreover, the paper offers an integrated volumetric and reservoir modeling for estimation of gas-in-place (GIP) in the studied interval of the Muerto formation. The calculated GIP, including adsorbed gas is 660.2 MSCF/(acre-ft). This is the first application of a multi-porosity model for an unconventional gas reservoir in Peru, thus offering a methodology for porosity modeling of other unconventional tight reservoirs in Peru where petroleum plays have been relatively underdeveloped. Our study mainly aims to quantify different porosities that control the estimation of total GIP in tight rock formations.