The Study Of Fractured Horizontal Well Optimization Design In Shale Gas Reservoirs

Shale gas is one of important unconventional gas resources and Clean green energy.The efficient development of shale gas not only alleviate the contradiction between supply and demand of China's oil and gas,but also reducethe environment pollution and greenhouse effect.China has vast land area and rich Shale formation,have the very good developing potential.However,domestic shale gas reservoir development is still in its infancy.There are few studies on shale gas reservoir horizontal well development andusing of horizontal wellstaged fracturing technology for shale gas reservoirsdevelopment is still in the exploratory stage.Research on horizontal well staged fracturing optimization design has an important role for guiding shale gas reservoir development.This paper offersa brief analysis and description on the basic geological characteristics and development characteristics of shale gas reservoir.Through the isothermal adsorption experiments and methane diffusion experiments for researchareacores,we got the Langmuir pressure,Langmuir volume and methane diffusion coefficient.Then,on the basis of geological data in the study area,and use the reservoir numerical simulation component module of Eclipse software,the shale gas reservoir horizontal Wells model and staged fracturing horizontal Wells model are established.Based on the horizontal Wellmodel,the influence of the geological parametersare simulated and analyzed,including the natural fracture permeability,matrix porosity,rock compressibility and SIGMAV,on horizontal Wells(no fractured)fifteen years cumulative production.Using the method of partial correlation,the impact of various geological parameters for horizontal well fifteen years cumulative productionareanalyzed.According to the related factors,correlation index from big to small are natural fracture permeability,SIGMAV,matrix porosity and rock ompressibility.After completion ofthe influenceof the cumulative production for fifteen years on geological parameters,using the staged fracturing horizontal Wells modle simulated and analyzed the influence of the artificial fracture parameters,including the fracture conductivity,fracture numbers,fracture halflength and fracture height,onstaged fracturing horizontal Wells fifteen years cumulative production.Using the method of partial correlation analyze the impact of various artificial fracture parametersforstaged fracturing horizontal Wellsfifteen years cumulative production.According to the related factors,correlation index from big to small arefracture halflength,fracture numbers,fracture conductivity and fracture height.Based on the analysis of influencingfactors aboutthe production capacity of horizontal well,artificial fracture parameters are optimized.First,changing artificial fracture number,such as 3,5,9,11,13,simulate and get the graph of the relationship between cumulative production for fifteen years and fracture conductivity.According to the graph,the fractureconductivityis optimized.Second,changing artificial fracture conductivity,such as 0.3048mD·m,0.6096 mD·m,1.524 mD·m,3.048 mD·m,6.096 mD·m,9.144 mD·m,simulate and get the graph of the relationship between fifteen years cumulative production and fracture number.According to the graph to optimize the optimal fracturenumber.After the optimization of fracture conductivity and fracture number,change artificial fracture halflength,such as 60 m,90m,120 m,150m,180 m,simulate and get the graph of the relationship between fifteen years cumulative production and fracture halflength.According to the graph to optimize the optimal fracturehalflength.Finally,according to the optimized parameters fracture conductivity,fracture number,fracture halflength,change the fracture height(13 m,23 m,33 m)simulate the 15 years cumulative production of horizontal well,optimize the best fracture height.Through analysis ofthe fracturing horizontal Wells,with horizontal section length of 1080 m,optimal 3 mD·m fracture conductivity,9 optimal fracture number,150 m optimal fracture halflength,23 m optimal fracture height.Make the graph of the relationship between the product of simulation ratio and fracture conductivity.Through the graph we can draw the following conclusions.thedemarcation pointof,which is the parameter in fracture conductivity,is 3 mD·m.To improve the product of simulation ratio,on the left sidepriority to increase fractureconductivity,on the right side priority to increase fracture halflength.According to the optimalresults of fracture parameters,fractured horizontal well pattern types are optimized.The well pattern optimization design considering four arrangement of the fracturing of horizontal Wells with Parallelhorizontal section.By changing the two horizontal well spacing,simulated the ten years cumulative production under four kinds of arrangement,optimized the best way of fracture arrengment and horizontal well spacing.According to the optimization of horizontal well fracture arrangement and spacing,we got the bestwell pattern type of fracturing horizontal well development by Comparing the rectangle well pattern and triangle well pattern.Fractured horizontal Wells in the study area present the best well pattern type of rectangle well pattern,wellhead in the same direction,artificial fractures distributed evenly and in the symmetrical,two parallel horizontal well have the optimal distance is about 500 m,along the horizontal direction optimal well spacing is about 1200 m.