IMPACTS OF ZONE FRACTAL PROPERTIES ON SHALE GAS PRODUCTIVITY OF A MULTIPLE FRACTURED HORIZONTAL WELL

A multiple fractured shale gas reservoir is divided into three zones, namely the single-porosity zone, the dual-porosity zone, and the hydraulic fracture zone. The distributions of pore size, fracture length, and fracture aperture vary in each zone and affect shale gas productivity. This paper developed a fractal numerical model to investigate the impacts of zone fractal properties on the shale gas productivity of a multiple fractured horizontal well. in this model, a fractal permeability model was developed, in which the diameter/aperture distribution of circular/slit pores arid the length of fractures all follow fractal scaling law. This numerical model was solved by finite element method within the platform of COMSOL Multiphysics and verified through the history matching of production data from the Marcellus and Barnett shale reservoirs. Finally, the effects of the fractal dimension (D-e, D-l, D-tau) and the maximum diameter (e(max)) of the pores on gas productivity (measured by gas production rate and cumulative gas production) were investigated. Numerical results show that increasing the maximum pore diameter e(max) can enhance gas productivity, but increasing the pore diameter fractal dimension D-e makes the gas productivity decrease and increasing tortuous fractal dimension D-tau decreases the gas productivity, too. The length fractal dimension D-l of fractures is sensitive to the gas flow in the dual-porosity zone.