Hydraulic Fracturing Optimization Of Tight-gas Reservoirs

With the increase in demand of fossil-fuel,economically producing gas from unconventional sources(tight gas,coal bed methane(CBM),and gas hydrate)is a great challenge today.This thesis focuses on the issues of hydraulic fracturing optimization of unconventional tight gas reservoir.Firstly,laboratorial experimentation was conducted to evaluate and analyze the gel agent and cross-linker selection and optimization under selected temperature for viscosity optimization of the fracturing fluids.Secondly,conductivity test of proppant was conducted to optimize proppant from four different manufacturers,analysis on optimization of proppant particle size(20/40,30/50,30/60 and 40/70)was done and proppant concentration optimization analysis between 5kg/m~2 and 10kg/m~2 under the condition of tight sand reservoir was conducted.Finally,compressible mathematical model was established to analyze the influence of fracture parameters(fracture length and fracture conductivity)and the operation parameters(the percentage of pre-liquid,sand ratio,displacement and sand concentration)for the production optimization analysis of the well.Hydraulic Fracturing can improve the conductivity capacity of low permeability reservoirs and hence increases the production and enhance natural gas production in the tight gas reservoirs.Composition of 0.4%of the gel agent and 100:0.4 of the cross-linker were chosen for fracturing fluid system optimization;ceramic proppant(20/40,10kg/m~2)was chosen for proppant optimization;the fracture length was optimized in three stages(K?0.01md:between 250m~300m),(0.01<K<0.1md:between 200m~250m)and(K?0.1md:between 150m~200m)and conductivity was optimized between 30?m~2?cm and 40?m~2?cm under tight gas condition;pumping rate of3.0-3.5m~3/min,sand volume of 40-50m~3,displacement volume of 3.5m~3/min were chosen for hydraulic fracturing operational parameter optimization.This study provides experimental and theoretical basis for the hydraulic fracturing optimization in unconventional tight gas reservoir.