Results of Large-dlqmeter Well Drilling in Philippine Geothermal Felds

4 large hameter casing design was adopted for 34 vells drilled in the Philippines using 13-3/8” mduction casing in combination with 9-5/8’ slotted iner to improve well output and to reduce space equirement in collaring the wells. Well test results ndicate an increase in production by as much as !50% compared with wells using the usual string ambination of 9-5/8” and 7-518”. In the 600 MWe q t e Geothermal project alone, a reduction of about 9 wells in the total number of wells to be drilled vas achieved because of this newly adopted casing :onfiguration. This translates to a direct savings of JS$23-48 million, excluding those saved from a) leveloping new production and reinjection pads; b) idditional pipeline length; c) damage to environment rom new areas. However, various drilling problems vere encountered associated with collapsing ormation and casing failures. These have been nitigated by appropriate drilling procedures, cementing and selection of casing materials.