A Summary of Geothermal Exploration and Data from Stratigraphic Test Well No. 1 Makushin Volcano, Unalaska Island

Abstract

Geothermal resource investigations have been conducted for the past four years on Unalaska Island in the Aleutian Chain. The focus of the work has been Makushin Volcano, about 12 miles from the cities of Unalaska and Dutch Harbor. In the summer of 1982, three widely spaced deep temperature gradient holes were drilled whlch encountered high temperatures. During the summer of 1983, a three inch diameter "sim hole" well, ST-1. was drilled to 1,949 feet. A shallow, low pressure, steam zone and a relatively productive hot water zone at total depth were encountered. The lower zone produced 47,000 lb/hr, limited by reachlng critical mass velocity at the orifice. The static bottomhole pressure and temperature were 478 pslg and 379'f, respectlvely. Analysis of transient pressure and flow data yielded a productivity index of 3,470 lb/hr/psi and a permeability-thickness of 50,900 md-ft for the three-foot (at the wellbore) lower zone fracture. A preliminary reservolr/wellbore flow evaluatlon for a posslble power plant lndicates two commercial size wells could fuel a 10 megawatt facility.