Results of Big-Hole Drilling in PNOC-EDC Geothermal Fields

Abstract

A large diameter casing design was adopted for 34 wells drilled in the PNOC-EDC geothermal fields using 13-318ÆÆ production casing in combination with 9-518ö slotted liner to improve well output and to reduce space requirement in collaring the wells. Well test results indicate an increase in production bv as much as 1700% compared with wells using the usual string combination of 9-53ö and 7-58ö, In the 600 Mie Leyte Geothermal project alone, a reduction of about 19 wells in the total number of wells to be drilled was achieved because of this neuly adopted cming configuration. This translates to a direct savings of CS323-48 million, excluding those smedfroni a) developing new production and reinjection pads; b) additional pipeline length; c) daniage to environment front new areas. However, various drilling problems were encounlered associated with collapsing formation and casing failures. These hove been mitigated by appropriate drilling procedures, cementing and selection of casing materials.