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The hydraulic fracturing of geothermal formations

Description: Hydraulic fracturing has been attempted in geothermal formations as a means to stimulate both production and injection wells. Since most geothermal formations contain fissures and on occasion massive natural fissures, the production behavior of the man-made fractures results in certain characteristic trends. A model is offered that allows the presence of a finite or infinite conductivity fracture intercepting a fissured medium. The method is based on a numerical discretization of the formation allowing transient interporosity flow. Type curves for pressure drawdown and cumulative production are given for infinite acting and closed reservoirs. Since most of the fissured formations exhibit a degree of anisotropy, the effects of the orientation of the hydraulic fracture with respect to the fissure planes, and of the ratio between the directional permeabilities are then discussed. Guidelines are offered as to the size of appropriate stimulation treatments based on the observed fissured behavior of the reservoir.
Date: January 1, 1988
Creator: Naceur, K. Ben; Economides, M.J. & Schlumberger, Dowell
Partner: UNT Libraries Government Documents Department

EVAULATION OF THE MAKUSHIN GEOTHERMAL RESERVOIR, UNALASKA ISLAND

Description: Analysis of an extended flow test of well ST-1 on the flanks of Makushin Volcano indicates an extensive, water-dominated, naturally fractured reservoir. The reservoir appears to be capable of delivering extremely large flows when tapped by full-size production wells. A productivity index in excess of 30,000 lb/hr/psi implies a phenomenal permeability-thickness product, in the range of 500,000 to 1,000,000 md-ft. The flowing bottomhole (1,949-foot) temperature of the fluid is 379 F, which is lower than the measured static temperature at that depth (395 F). This phenomenon, coupled with an observed static temperature gradient reversal from the maximum 399 F observed at 1,500 feet, indicates that the reservoir proper is located some distance from the well. presumably it is at a temperature slightly lower than 379 F and communicates with the wellbore via a high conductivity fracture system. A material balance calculation yields an estimate of reserves that are capable of sustaining all of the present power needs of the island (13 {+-} MW peak) with a geothermal power plant for several hundred years. Theoretically, a single large diameter well at the site of ST-1 could satisfy this requirement.
Date: January 22, 1985
Creator: Economides, M.J.; Morris, C.W. & Campbell, D.A.
Partner: UNT Libraries Government Documents Department

Resource Evaluation and Development Plans for a 120 MW Geothermal Power Plant on Milos Island, Greece

Description: Five deep wells have been drilled on the Island of Milos, Greece, identifying a high-temperature, high-enthalpy geothermal reservoir. The thermodynamic properties of the fluid, and the estimated porosity and presumed thickness of the formation suggest a fluid and heat storage capacity that could support a 60 MWe power plant for 85 years or a 120 MWe for half that time. The existing five wells can deliver 180 t/h of steam at 10 bar abs pressure, capable of generating a maximum electric power output of slightly less than 20 MWe. This paper describes the geology, the drilling and the well testing results pertaining to the five wells, and discusses the reservoir potential for a 60 MWe geothermal power plant.
Date: December 15, 1983
Creator: Economides, M. J.; Ehlig-Economides, C. A.; Speliotis, G. & Vrouzi, F.
Partner: UNT Libraries Government Documents Department