Study On Multi-field Coupling Theory And Its Application Of Hydraulic Fracturing And Solution Mining For Salt Deposits

Salt deposits are a special kind of deposits, which enjoy high mining and utilizing values. Not only the minerals contained in them are valuable chemical industry materials, which paly important roles in our natioanl economy and social lives, but also their mined cavity are considered to be ideal hosts for oil and gas storage underground due to their advantageous geologic and mechanical characteristics. So scientific mining thoery and technology for salt deposits are always an indispensable foundation or guarantee for rational exploiting and utilizing them.As salt minerals are easily dissolved in water, solution mining method is commonly adopted for salt deposits mining. However, to found a scientific and comprehensive solution mining theory system is much difficult and consequently to further the current solution mining technology is heavily resticted because that the solution mining process of salt deposts is a complicated multi-field coupling problem, which involves fluid flow, mineral dissolution, heat and mass transfer, solid deformation, and so on. So, the research on multi-field coupling theory and application of solution mining for salt deposits is greatly significant and meaningful for scientifically theorizing and rationally exploiting for the deposits.In this dissertation, the study on the multi-field coupling theory and its application of hydraulic fracturing and solution mining for salt deposits is carried out in the following aspects. (1) The experimental study on pysical and mechanical characteristics of both intact and damaged rock salt samples under different temperatures raging from 20 # to 240 #; (2) The study on theory and technology of hydraulic fracturing and dissolving of salt deposits based on solid deformation, fluid flow, mineral solution and solute diffuse coupling analysis; (3) The foundation of mathematical model of solid deformation, fluid flow, heat and mass transfer coupling for solution mining of salt deposits, and numerical simulations of the model; (4) The simulated experimental study on double-well convection and multi-well hydraulic fracturing and solution mining in the laboratory; (5) The technology of multi-well hydraulic fracturing and controlled solution mining and its in situ test in thenardite mining of Yuncheng Salt Lake; (6) The primary analysis and discuss on oil and gas storage and wastes disposal in salt deposits.Through systematic studyies in this dissertation, main obtained conclusions are asfollows: (1) Thenardite rock salt is a soft rock and temperature effects on its mechanicalcharacteristics are remarkable. With tempearture increasing, both the mechanical strengthand plastic deformation of the samples are enhanced to certain degree; (2) Hydraulicfracturing in salt deposit is a complex and coupled process, which is involved with rockfracture, solid deformation, fluid flow, salt mineral solution, solute diffusion and so on,numerical simulation of which demonstrates that the fracture opens in a fan shape and therelation of fracture aperture(w) with distance(x) and time(t) is w = (0.0034 +0.0006t) e(0.0007+0.0018t)x; (3) The solution mining process is a complicated process, which isinvolved with fluid flow, mineral solution, solute diflusion, heat and mass transfer, andsolid deformation; it is a multi-field coupling procedure. The results of correspondingnumerical simulation well demonstrate their relations; (4) During solution mining process,the relation between dissolving rate and dissolved area of salt deposits is in the form ofexponential law, and the dissolving rate increases with the flow speed of the brine to someextent; Hydraulic fracturing can make crake expand along the weak interlayer in saltdeposits and wells connect easily; (5) The technology of multi-well hydraulic fracturingand controlled solution mining of salt deposits is an economiocal and feasible method, theeffect of which is well demonstrated by its application in thenardite mining of YunchengSlat Lake; (6) The cavern constructed with the...