BUREAU OF MINES INFORMATION -CIRCULARj1989 In Situ Leach Mining Proceedings: Bureau of Mines Technology Transfer Seminars, Phoenix, AZ, April 4, and Salt Lake City, UT, April 6, 1989 UNITED STATES DEPARTMENT OF THE INTERIOR Information Circular 9216 In Situ Leach Mining Proceedings: Bureau of Mines Technology Transfer Seminars, Phoenix, AZ, April 4, and Salt Lake City, UT, April 6, 1989 By Staff, Bureau of Mines UNITED STATES DEPARTMENT OF THE INTERIOR Manuel J. LUjan, Jr., Secretary BUREAU OF MINES TS Ary, Director PREFACE In April 1989, the U.S. Bureau of Mines held technology transfer seminars on in situ leach mining at Phoenix, AZ, and Salt Lake City, UT. The papers presented at those seminars, as well as three reports of related research, are contained in this Information Cir­ cular. The papers highlight various aspects of Bureau research on in situ leach mining, in­ cluding a field experiment in copper leaching in Arizona and the use of computer programs to model physical and chemical parameters involved in in situ mining. The technology transfer seminar used as a forum for the transfer of this research is one of the many mechanisms used by the Bureau in its efforts to move research developments, technology, and information resulting from its programs into industrial practice and use. To learn more about the Bureau's technology transfer program and how it can be useful to you, please write or telephone: U.S. Bureau of Mines Office of Technology Transfer 2401 E Street, NW. Washington, DC 20041 202-634-1224 iii CONTENTS Page Preface . Abstract 1 Introduction ............................................................................................... 2 In Situ Copper Mining Field Research Project, by Jon K. Ahlness and Daniel J. Millenacker ........................... 4 Generic Design Manual: Cost Model for In Situ Copper Mining, by Joseph M. Pugliese. .............................. 7 Introduction to the Environmental Permitting Process for In Situ Copper Mining, by Daniel J. Millenacker .............. 14 Laboratory Core Leaching and Petrologic Studies To Evaluate Oxide Copper Ores for In Situ Mining, by Steven E. Paulson and Harland L. Kuhlman '" , '" ." ". .. ... .. ... 18 Methods for Determining the Geologic Structure of an Ore Body as It Relates to In Situ Mining, by Linda J. Dahl. ....... 37 Computer Modeling Applications in the Characterization of In Situ Leach Geochemistry, by Dianne C. Marozas ......... 49 Modeling Infiltration to Underground Mine Workings During Block-Cave Leaching, by Robert D. Schmidt. ............ 58 HydroLogic: An Intelligent Interface for the MINEFLO Hydrology Model, by Michael E. Salovich .................... 67 Predicting and Monitoring Leach Solution Flow With Geophysical Techniques, by Daryl R. Tweeton, Calvin L. Cumerlato, Jay C. Hanson, and Harland L. Kuhlman. ........................................................ 73 Enhanced Well-Drilling Performance With Chemical Drilling-Fluid Additives, by Patrick A. Tuzinski, John E. Pahlman, Pamela J. Watson, and William H. Engelmann , " '" . .. .. .... 86 UNIT OF MEASURE ABBREVIATIONS USED IN THIS REPORT atm atmosphere, standard L/min liter per minute °C degree Celsius M molar c/lb cent per pound m meter cm centimeter mD millidarcy cm2 square centimeter MHz megahertz cm3 cubic centimeter min minute cP centipoise mL milliliter D darcy mLimin milliliter per minute ft foot mm millimeter ft2 square foot lim micrometer ft/mi foot per mile limho/cm micromho per centimeter ft/min foot per minute mm/min millimeter per minute ft/s foot per second mol mole g gram mol/L mole per liter galld gallon per day MPa megapascal (galld)/ft2 gallon per day per square foot ms millisecond gal/min gallon per minute mt metric ton g/cm3 gram per cubic centimeter mt/yr metric ton per year giL gram per liter mV millivolt h hour pct percent Hz hertz ppm part per million in inch psi pound (force) per square inch Kbyte kilobyte (l,024 bytes) rpm revolution per minute kg kilogram s second km/s kilometer per second st/d short ton per day kW kilowatt st/yr short ton per year L liter wt pct weight percent lb pound yr year lb/st pound per short ton $/yr dollar per year Llh liter per hour The Bureau of Mines expressly declares that there are no warranties express or implied that apply to the software discussed in this report. By acceptance and use of said software, which is conveyed to the user without consideration by the Bureau of Mines, the user expressly waives any and all claims for damage and/or suits for or by reason of personal injury, or property damage, including special, consequential or other similar damages arising out of or in any way con­ nected with the use of the software discussed herein. IN SITU LEACH MINING Proceedings: Bureau of Mines Technology Transfer Seminars, Phoenix, AZ, April 4, and Salt Lake City, UT, April 6, 1989 By Staff, Bureau of Mines ABSTRACT As part of its research on advanced mining technology, the U.S. Bureau of Mines em­ phasizes studies on in situ leach mining. This research enables the Bureau to develop technical information that can allow mining companies to adopt in situ leach mining methods. Research results should help to remove the technical and economic barriers cur­ rently hindering the development of commercial in situ leach mining operations. This report contains papers summarizing results of Bureau research on various aspects of in situ leach mining. A featured topic is the cooperative field experiment of the Bureau and Santa Cruz Joint Venture in a copper deposit near Casa Grande, AZ. Discussions in­ clude an overview of the entire project, cost modeling, environmental permitting, laboratory core-leaching experiments, petrographic studies, and an evaluation of the geologic structure in the region. In addition, papers describe hydrologic modeling and geophysical studies of solution flow during leaching. Preliminary geochemical modeling studies are also sum­ marized. A final paper describes a nonionic chemical additive with potential for significantly reducing the high costs of drilling in in situ leach mining. 2 INTRODUCTION During the 1980's, the V.S. minerals industry found it dif­ tions, profoundly alter environmental impacts, and reduce ficult to compete with foreign mining companies in world waste have moved to the forefront of Bureau research. markets. The V.S. copper companies were high-cost producers One of these new methods is called in situ leach mining. In in a shrinking world market. Copper mining companies began situ leach mining involves circulating dilute chemical solutions restructuring in order to survive. The restructuring included through an ore deposit to dissolve the target metals. The solu­ considerable closures to match production with lower demand. tions may be applied to the top of the ore body and allowed to Closing inefficient operations and adopting new processing seep down through it by gravity. Or the solutions may be technology enabled companies to boost productivity. This pro­ forced through the ore between series of vertical injection and ductivity, coupled with recent changes in the foreign exchange recovery wells (fig. 1). This method is sometimes referred to as rates of the V.S. dollar, returned many V.S. copper producers "true" in situ leach mining. In yet another variation, leach to better fiscal health. solutions are trickled over rubbled ore in stopes or other The present favorable market conditions will not, underground openings. Regardless of the application method, however, last forever. Major foreign companies also cut costs the solutions containing the dissolved metals are then pumped with considerable restructuring. V.S. companies remain high­ out of the ground and to a plant for metal recovery. After cost producers. For continued existence, the V.S. companies removing the metals from solution, operators recycle the solu­ must be able to sell mineral products at the same price as do tion back to the ore body. In situ leach mining thus combines foreign companies and still make a profit. Low ore grades, mining and processing operations. high labor rates, strict regulatory constraints, higher concern In situ leach mining offers several economic, safety, and over miner health and safety, and more costly environmental environmental advantages over conventional mining. The safeguards all force V.S. mining costs upward. During the Bureau believes that the method requires less capital invest­ next market contraction, V.S. companies will again be par­ ment. By eliminating ore extraction and crushing, in situ leach ticularly vulnerable. Most of the restructuring during the early mining also saves labor and energy costs. Other benefits in­ 1980's was a one-time cure; similar actions will not likely be clude fewer health and safety risks as miners will not be ex­ available to these companies in another down market. The posed to the hazards of underground mining. The technique Bureau of Mines believes that the industry needs new disrupts the environment less than does conventional mining; technology to overcome the high cost of conventional mining in situ leach mining removes little from the ground except the operations. target metals. It also leaves a mine site that is easily reclaimed The Bureau recently expanded its efforts to provide to its original condition by capping wells and dismantling the technology that will help the minerals industry develop the processing plant. necessary new mining and processing methods. Bold new The big question with the method is the metal recovery. methods of mining that improve worker productivity, Operators experienced low recovery from shallow rubbled minimize worker exposure to hazardous underground condi- deposits that were leached in the 1970's. Bureau experiments, Injection Recovery Processing plant well ( well Figure 1.-Cross section of an in situ leach mining system in which the ore is leached via a system of vertical wells. 3 however, indicate that certain deposits should leach well. Such over the past 5 yr and also includes the results of relevant cop­ results underscore the necessity of conducting the tests and per block-cave leaching research.