Hot Dry Rock Research A Compendium of Publications October 1989 - September 1990

Abstract

geothermal energy project are collected in this compendium. 1 Titles of papers are given in the DISCLAIMERPortions of this document may be illegible in electronic image products. Images are produced from the best available original document. Reservolr Development and Seismic MonitoringHDR reservoirs arr created using the same highpressurehydradicstimulatiun techniquesthatarecommonly employed in the petroleum industry, but g e n d l y on a much l a q~ d e . Fluid pressure is used tooparanarrayofp~stingjointswithinadeep, hot region of cmstal todc, forming a multiply connested series of flow paths that individually may have relatively high flow impedance, but that in aggregate result in slow overall flow impedance between the injection and productim wells. The d t i n g HDR reservoir comprisesaverylargebodyof fracturedrodc,approad.ling a cubic kilometer or more Based on the pioneering work at Lob Alamos, the analysis of pressureindud microseismicity has becmetheprincipaltoolusedindeterminingtheshape and orientation of an HDR reservoir as it is being ueated, as well as significant features of its internal structure (Albright and Hanold, 1976; Albright and Pearson, 1982; House and others, 1985; House, 1987; Fehler and others, 1987). The p&se locations of the numerous individual microearthquakes, which are generated as preexisting joints dilate and experience small amounts of associated shear displacement, are detmnined by detailed seismic analyses. One technique applies a statistical algorithm to the data set, normally comprised of several thousand individual events, to determine the most probable planes [Le., joint orientations) upon which shear displacement has occurred. This tedmique is referred to as the three-point method (Fehler and others, 1987; Fehler, 1989). The use of miaweisaniaty to determine the shape and struclure of pressurPstimulated reservoir regions is now also an important aspect of both the British and Japanese HDR programsIn 1985, IAX Alamos demowtrated that the pints identified in the microseismic data were major paths of fluid flow. Following several unsuccessful attempts to cmnnect two wells by hydraulic fracturing, the upper well (EE-3) was redrilled diagonally through the mimseismically active region generated when the reservoir was initially created from the lower well (EE-2). During this redrilling, a number of flow connections to the lower well were confirmed which corresponded to joint orientations identified in the mimseismic data.This experience, requiring redrilling to establish adequate flow communication across the reservoir, has led us to condude that an HDR system would probably best be developed in several stages, with the drilling of the production well(s) being delayed until an initial reservoir is created from the first well drilled (normally the injection well]. In this way, the production wellbore(s) could be located optimally on the surface based an the seismically determined orientation of the initial m o i r using only a near-surface array of geophones. These pro...

Studies of Transport Properties of Fractures: Final Report

“…Fluid flow in fractured rocks is a subject of primary importance to hazardous waste isolation, environmental remediation, oil and gas production from fractured reservoirs, reservoir stimulation by hydrofracturing, geothermal energy extraction, and the formation of vein fillings and ore deposits [e.g., Nelson, 1985;Burns, 1990;USGS Red-Book Conference, 1993;Committee on Fracture Characterization and Fluid Flow, 1996]. For these reasons, considerable effort has been placed on the characterization and modeling of flow in fractures and fracture systems.…”