Research On Thermo-Hydro-Mechanical Coupling Model For Oil Shale In-situ Exploitaition And Hydraulic Fracturing

Oil shale is the unconventional resource which has huge reserves, and it is also the main substitution for oil. Although the technology of ground carbonization is developed well nowadays, it has serious pollution with lots of waste solid and occupied large area of fertile farmland. Hence, it is necessary to develop the underground technology of carbonization. This dissertation studies the in-situ technology of oil shale and the technics of hydraulic fracturing for oil shale aiming at low permeability of oil shale.First of all, it has the experiments on basic property of oil shale, extrapolating the mechanical damage variable and the chemical damage variable. Basing on traditional hypothesis of equivalent strain and uniaxial compressive curve of stress-strain for oil shale, establishes mechanical damage variable. In the same way, according to pyrolysis experiments of oil shale, chemical damage variable can be defined.Second of all, it builds the multi-field mathematical model of oil shale considering damage variables, and simulates the in-situ carbonization. The mathematical models take the thermal-plastic damage, convection and phase change of kerogen, as well as the parameters in equations are the function of temperature into consideration. From the simulation, it gets: after 2 years, investments are more than interests from oil exploitation.Third of all, using weibull distribution function evaluates parameters for coefficient of thermal expansion, thermal conductivity, specific heat, modulus of elasticity, tensile and compressive strength etc. From the simulation of thermal fracture, it has: temperature field, stress field and deformation field are changed randomly, and the rules of thermal fracture in simulation are the same as the results of experiment in laboratory.Last but not least, it simulates the process of hydraulic fracturing by COHESIVE ELEMENT and SUBROUTINE in ABAQUS. It concludes: S11 mainly distributes the place of borehole and it has great influence on bedrock, while S22 and S33 have little impacts. In addition, leak-off volume rises, but rate reduces. All above results can guide in-situ carbonization of oil shale. Fracturing of rock can create the pass for pore fluid, and the in-situ exploitation of oil shale is win-win technology which can develop economy and also can protect environments.