Characterization of Hululais Subsurface Rock Formation and Its Implication to Strato Volcano Facies Model Hululais Geothermal Field, Indonesia

Abstract

Hululais geothermal field is located in Lebong district, Bengkulu province, Sumatera island, Indonesia. As one of the exploration field operated by Pertamina Geothermal Energy (PGE), Hululais geothermal field targeted to generate 2 x 55 MW electricity by the end of 2020. 24 wells have been drilled since 2010. Retrieved cutting and cores from the drilling wells are the primary data for subsurface modeling. Thus, its identification and characterization is important for the next field development scenario.
An updated new subsurface rock formation is successfully established. They are identified as Upper Suban Agung Volcanic (USAV), Lower Suban Agung Volcanic (LSAV), Hululais Volcanic (HV), Hululais Granodiorite Intrusions (HGI), and Seblat Metasediment (SM). Its unique characters and its huge implications for the field development scenario will be explained in this paper. The knowledge to identify these rock formations will increase success ratio of well drilling, and reduce potential hazard and loss.