Research On Optimization Of Staged Fracturing Parameters Of Horizontal Wells In Tight Gas Reservoirs Based On Microscopic Pore Structure

The development potential of tight gas reservoirs in C hina is very large,and its resources are more abundant than conventional natural gas.Fracturing techniques are often used to increase production to solve the problem of difficulty in the development of tight gas reservoirs due to limitations of objective factors such as tight reservoir rocks,small porosity,and poor seepage.Therefore,the optimal fracturing parameters should be found for the target area to achieve the maximum horizontal well productivity when satisfying economic benefits and construction difficulties.The article is based on the results of the conventional mercury injection test and the constant-speed mercury injection test,this paper plots the mercury injection curve.Classify the curvilinear form effectively corresponding rock space types,filter out the main reservoir types in the target area,and conduct further research on major types of reservoirs;establish differential gas-water two-phase seepage differential equations in tight gas reservoirs,the weak equations of the gas and water pressure equations and the equations that take into account the starting pressure gradient and the compression coefficient are given respectively;using FEPG finite element software,the weak form of the equation w as introduced to create a meshing map.The numerical simulation method was used to optimize the parameters of horizontal well fracturing in the target region,and the optimal scheme was finally given.The results show: the average throat radius of cores with permeability less than 1×10-3?m2 is mainly below 1?m,and the average throat radius of cores with permeability greater than 1×10-3?m2 is mainly above 1?m;the types of rock reservoirs are classified into four types according to their mercury injection curves: mesoporosity,dissolved pore-intergranular,intergranular and microporous;according to the distribution frequency of the constant-speed mercury intrusion test,the main pore distribution is estimated to be about 0.5 ?m,the reservoir type of the target reservoir is mainly intercrystalline pores,the average porosity is 4.8%,and the average permeability is 0.4×10-3?m2;comprehensive consideration of economic benefits and construction difficulty factors,the final selection of the optimal parameters for the horizontal well section with 5 cracks,the cluster number of 2 clusters,bottomhole flow pressure 8MPa,crack length of 200 m,the fracture width is 5mm;increasing the fracture length and bottomhole flow pressure can greatly increase the horizontal well production,while the increase in the number of clusters does not contribute much to horizontal well production.The conclusions of the study have certain guiding significance in the fracturing construction and enhanced oil recovery of tight gas reservoirs.