Evaluation of Shadow Stress between Hydraulic Fractures

In order to increase the productivity of extraction of hydrocarbons reservoirs, the well is usually drilled in the direction of the minimum horizontal in situ stress and hydraulic fractures simultaneously initiate and propagate perpendicular/transverse to the wellbore. The last decade, more than 10,000 horizontal wells per year have been bored and hydraulically fractured, with up to a hundred hydraulic fractures placed in the horizontal segment of the well. The well is therefor stimulated in stages, with one stage consisting of a single pumping operation aimed at initiating and propagating simultaneously typically between3-8 cracks spaced about 10–30 m apart. When, the fluid pressure is applied on the surface of the fracture, the crack can propagate in the medium, but the pressure, induced from fluid injection, may have a negative influence on the extension of adjacent cracks which is stated as shadow or interaction stress. Certainly, an accurate estimation of interaction/shadow stress between the cracks leads to a more optimal design. In this research, the effect of the interaction between the hydraulic cracks with respect to the spacing and the number of cracks on the each other and considering position of the fractures are evaluated using the enhanced pseudo traction method. The results are shown that inner-fractures are further affected from shadow stress compared to outer-fractures. On the other hand as distance of hydraulic fractures increases, shadow stresses decrease. In the last, the results can be useful in determining the optimum number and spacing of cracks in the design of hydraulic fractures.