Evaluation of Shadow Stress between Hydraulic Fractures

Document Type : Research Article


1 Assistant Professor of Geotechnical Engineering, Faculty of Engineering and Technology, University of Mazandaran, Babolsar, Iran.

2 Department of Civil and Environmental Engineering, Tarbiat Modares University, Tehran, Iran.


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. In 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. In order to reduce operational cost, it is usual to create several hydraulic fractures at once. The well is there for stimulated in stages, with one stage consisting of a single pumping operation aimed at initiating and propagating simultaneously typically between 3-8 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 the 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 each other and considering the position of the fractures are evaluated using the pseudo traction method. The results are shown that inner-fractures are further affected by shadow stress compared to outer-fractures. On the other hand as the 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.


Main Subjects

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