Experimental Study And Numerical Simulation Of Sealing Grouting For Oil Shale In-situ Pyrolysis

In situ pyrolysis of oil shale needs to provide a channel for migration of shale oil and gas produced by pyrolysis of oil shale.The oil shale in situ pyrolysis technology is required in a high temperature and high pressure conditions,the oil shale pyrolysis reaction area of groundwater is produced by hydraulic fracturing fracture into the reaction zone caused by heat medium most of the heat absorbed by groundwater and the influence of oil shale pyrolysis,in addition,rock pyrolysis products of oil shale with the groundwater migration to the external environment will cause soil and water environmental pollution.In view of the above problems,this paper presents a closed pyrolysis of oil shale in-situ sealing grouting formula technology and grouting material,is intended to provide a closed space to avoid the above problems for oil shale in situ pyrolysis,and improve energy efficiency,reduce the in-situ oil shale on environmental pollution.Firstly,the formation process and morphological analyses of oil shale fractured,fractured shale fracturing that Nong’an oil shale mostly existed in the direction parallel to the slit height,for the majority of 0.16 mm,a large number of proppant and fissures.The fracture of oil shale is similar to that of common fracture and porous media.Because of the oil shale in situ pyrolysis process needs under high pressure and high temperature environment,and oil shale fracture is less than 0.2mm,under the condition of ordinary Portland cement grouting material and chemical grouting material is not suitable for oil shale fracture grouting.After the primary election,the formula of grouting material is composed of special superfine cement,micro silicon,Hydroxypropyl Methylcellulose and sodium gluconate.Through the analysis of water four factors and three levels orthogonal test of formula of slurry rate,stone rate,viscosity,uniaxial compressive strength,rheological properties of slurry concretion were tested and analyzed,and ultimately determine the optimal formula for silicon content is 10‰,Hydroxypropyl methyl cellulose content was 0.6‰,the dosage of sodium gluconate 0.6‰,ratio of water and cement is 0.8.Using FLUENT to study the diffusion rule of the formula slurry in the oil shale fracture.The actual oil shale layer grouting construction,in order to prevent the reaction in the area around the grouting through cracks into the reaction zone will reflect regional fracture blocking effect of oil shale in-situ pyrolysis process,need to continue to inject gas at high pressure grouting at the same time.Therefore,the influence of gas injection pressure on the diffusion radius is considered in the numerical simulation,and the influence of ratio of water and cement,grouting pressure,fracture height and gas injection pressure on the diffusion range of slurry is studied by numerical simulation.Containing proppant fracture is simplified as porous media model,after a large number of numerical simulation to determine the impact of the above factors have on grout diffusion,the grouting pressure,ratio of water and cement and gas injection pressure of grout diffusion radius has great influence.Because of the effect of high pressure gas,the slurry diffusion is fan-shaped,and the distribution is related to the gas injection pressure and grouting time.The fracture height is 0.16 mm,the ratio of water and cement is 1.2,the grouting pressure is 0.8MPa,the injection pressure is 0.8MPa,and the grouting time is 20 min,the maximum diffusion radius is 0.57 m,and the minimum diffusion radius is 0.28 m.Underground hydrological data required for the Nong’an oil shale base grouting construction made of the two methods of using high density resistivity method and cross hole elastic wave CT of geophysical prospecting to Nong’an oil shale base,the results showed that there were rich water structure in the 160m~420m line,the construction of NE40 degrees left and right.Through the investigation of groundwater around the project area,it is known that the groundwater flows from southwest to northeast,and the flow direction is about 42 degrees east of north.According to the survey results of the project area water grouting scheme was designed,put forward a kind of oil shale in situ pyrolysis of closed type sealing grouting technology,the main contents of this technology is the establishment of a closed curtain grouting in the upstream project area mining area of oil shale in the direction of the water,the bottom plate and a top plate to form a closed grouting area.According to the permeability of the rock layer obtained by the water pressure test and the parameters of the formula in the laboratory test,the diffusion radius,the distance and the layout of the grouting hole are designed.According to the design scheme of sealing grouting technology is closed,the sealing grouting test in In-situ pyrolysis process of Nong’an oil shale project base.Through the construction of I sequence and II sequence of grouting hole of oil shale,oil shale and oil shale rock bottom roof for a period of 20 days after the end of grouting construction,the construction of each test area of rock permeability were tested,test results show that the test area of each rock permeability is greatly reduced and the effect of grouting sealing obviously.To form a closed system for the purpose of sealing grouting.