Use of Wellbore Simulation as a Tool to Evaluate Well Issues in Mature Geothermal Fields

Abstract

The Tiwi and Mak-Ban Geothermal Fields in the Philippines have been on commercial production for over 30 years and are considered to be “mature” assets in terms of their commercial development. This paper discusses how Chevron Geothermal uses wellbore simulation to add quantitative analyses to conceptual well models in order to justify wellwork. “GeoFlow”, a software developed in-house, is introduced as the tool used for simulation. The simulation process, from data requirements to the correlations used, is briefly noted. Four specific examples, Kap-29, Nag-20, Bul-65, and Bul-01 are discussed. Wellbore simulation enabled the company to estimate steam production addition from Kap-29 and Bul-01, and thus approve their workovers. Nag-20 is projected to be a good candidate for an injection well. Bul-65’s workover, on the other hand, was postponed due to findings from the simulation. The case of Bul-01 also highlights the criticality of a robust and truthful conceptual well model as a requirement before proceeding with wellbore simulation, as simulation results are not unique and changing wellhead conditions can be the result of more than one subsurface process.