The influence of fracture properties on ground-water flow at the Bunker Hill Mine, Kellogg, Idaho

PROPERTIES:TIME DEPENDANCE

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944090 Analytical and numerical modeling of high p r e s s u r e fluid-rock mechanical interaction in HDR eothermal energy reservoirs • J. Pine & D. A. C. Nicol, in: Comprehensive rock engineering. Vol. 5, ed J.A. Hudson, (Pergamon), 1993, pp 523-546. An aspect of fundamental importance of Hot Dry Rock (HDR) is the interaction of high pressure fluid injections ('stimulations') with the naturally stressed, jointed host rock mass. This chapter is concerned mainly with analytical and numerical models developed to study this interaction. The main variables considered in the modeling are: joint orientation, spacing, aperture, shear and normal compliance, shear strength, dilation, and connectivity; rock mass deformability; fluid flow regime in joint networks; far field stress and hydraulic boundary conditions. The modeling gives insight into: observed pressure histories during major fluid injections; development of patterns of joint stimulation and microseismic activity; enhanced permeabilities (short and long term); passage of fluid pressure and stress through the rock mass. The numerical models developed are all part of the FRIP suite (Fluid-Rock Interaction Program); a series of one-, two- and threedimensional finite difference coupled fluid flow/rock stress models. -from Authors

smaller discharge rate fluctuations observed in the drift. Individual f r a c m r e p m p e r t i e s were characterized on a smaller scale of analysis for each set of subparaliel fractures. -from Author

944091 Perforation and stimulation design for deviated wells at the K u p a r u k River field, Alaska C. M. Pearson, J. H. Schmidt & Ching H. Yew, in: Comprehensive rock engineering. Vol. 5, ed J.A. Hudson, (Pergamon), 1993, pp 641-652. Sixty-five percent of the reserves of the Kupamk River Field, the second largest producing oil field in the US, are contained in a 20-80 mD (1 m D = 9.869 × 10.4 ~tm2) permeability sandstone. This chapter provides details of how an understanding of rock mechanics principles impacts the stimulation practices and ultimate productivity from this field. Three key areas axe discussed: the perforation requirements from the deviated wellborers, the selection of a suitable ~.roppant material and the formation characteristics which limit the size of the stimulation treatments -from Authors

944095 Creep effects on static and cyclic instability of g r a n u l a r soils P.V. Lade, Journal of Geotechnical Engineering - ASCE, 120(2), 1994, pp 404-419. Presents a series of experiments conducted on loose sand that compresses during shear. In these tests the sand is allowed to creep over different periods of time resulting in movement of the yield surface• The influence of the new location of the yield surface on the static and cyclic instability of the sand is studied and discussed. -from Author

944092 Case study of hydraulic fracture experiments at the Multiwell Experiment site, Piceance Basin, Colorado, USA N. R. Warpinski, in: Comprehensive rock engineering. Vol. 3, ed J.A. Hudson, (Pergamon), 1993, pp 811-837. This chapter begins with a review of hydraulic fracturing and its importance for the Multiwell Experiment and a geological overview. The in situ stress, rock property and pertinent lotg data are reviewed for the well as a whole or for specific mtervals. The main body of the chapter consists of a discussion of data and results from the five stimulation experiments, the types of calibration fracturing tests performed in each interval, the analysis of the stimulation data and the final results. The chapter concludes with a recommended methodology for conducting stimulations in lowpermeability formations. -from Author 944093 The influence of fracture properties on r o u n d - w a t e r flow at the Bunker Hill Mine, Kellogg, aho T. E. Lachmar, Bulletin - Association of Engineering Geologists, 30(4), 1993, pp 395-407. The Bunker Hill Mine in northern Idaho is a large underground lead-zinc mine located in Precambrian metaquartzite rocks with virtually no primary porosity. Ground-water flow through these types of rocks is largely dependent upon the properties of fractures such as joints, faults and relict bedding planes. Ground water that flows into the mine via the fractures is contaminated by heavy metals and by the production of acid water, which results in a severe acid mine drainage problem• Fracture mapping techniques were used to obtain detailed information on the fracture rties observed in the Hew East Reed drift of the er Hill Mine. The results indicate that: 1) three structural domains exist in the New East Reed drift, and 2) a change in structural domains alone is not causing the relatively large fluctuations in discharge rates observed in the drift. However, structural domains may be influencing

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944094 Hydraulic fracturing - the significance of /n s/tu stresses and rock mechanics R . W . Veatch Jr & Z. A. Moschovidis, in: Comprehensive rock engineering. Vol. 5, ed J.A. Hudson, (Pergamon), 1993, pp 617-628. The present chapter illustrates some of the practical considerations of constructing the in situ stress profile in the vicinity of a welibore employing simple rock mechanics solutions. This particular example is from an actual case study of a well in the North Sea. The procedure presents some of the engineering assumptions required to derive the closure stress profile from microhydraulic fracturing, RFT, and general formation data. Finally, a three-dimensional fracture simulator is applied to predict fracture geometry, and provides an explanation for premature screen-out and recommendations to complete a fracturing treatment successfully. -from Authors

Time dependent behaviour

944096 Time-dependent behavior of rocks M. B. Dnsseank & C. J. Fordham, in: Comprehensive rock engineering• 1Ioi. 3, ed J.A. Hudson, (Pergamon), 1993, pp 119-149. Laboratory creep testing of rocks for parameters useful in design generally requires a test program which examines the specific effects of the range of conditions expected in situ. The results can then be used to develop a semiempirical model to predict the behavior of the material in situ. To perform a laboratory deviatoric creep test, high quality representative samples are used to prepare test spectmens, which are isotropically loaded to a stress equal to or greater than in situ to reverse some of the sampling damage. A deviatoric load is applied to the specimen and the deformation monitored. Other test configurations are ~ossible such as relaxation tests, or other stress or strata-rate controlled configurations. Data may be analyzed for transient response and steady-state creep. -from Author 944097 The phenomenon a n d examples of rock creep H. Ito, in: Comprehensive rock engineering• Vol. 3, ed J.A. Hudson, (Pergamon), 1993, pp 693-708. This chapter looks at long term rock creep under small stresses. Three long term experiments (in 1957, 1974, and 1980) have been carried out bending rock beams under bending stresses smaller than 2.5 MPa. It is emphasised that cree~ takes place in compressional and tensional regimes, urom the general creep trend, the Youna's moduli for the initial an(i final elastic deformation~ and the viscosity can be determined. A phenomena noted and emphasised here, is creep reversal - that is the creep curve of rock has an undulating contour, and a hypothesis of adjusting strain energy is presented. -R.Gower 944098 The importance of creep and time-dependent dilataney, as revealed from ease r e c o r d s in China Tan Tjong Kie, in: Comprehensive rock engineering. Vol. 3, ed J.A. Hudson, (Pergamon), 1993, pp 709-744. This chapter details the effects of creep and dilatancy in two case studies from China. After a brief introduction to theological testing, the first case study on the long term limit stability of the Ghe Zhou Ba dam is presented. Topics raised include the geomechanical setting, the testing programs undertaken, the theological models, and the founda-