Multi-stage fractured horizontal wells have been widely applied to develop tight oil and gas reservoirs, while there is a long topic about stress shadow effect in multi-fracture propagation geometry induced by horizontal-well stimulation in different fracture distribution patterns. Therefore, it is very important to reveal stress shadow effect existing in the processing of hydraulic fracturing treatment in horizontal wells. In this paper, a new non-planar fracture stress interference calculation model was established by means of the displacement discontinuity boundary element method. Influence factors analysis showed that:

  1. The Young's modulus of rocks and horizontal principal stress difference are the important factors to stress shadow in reservoir geological parameters which can increase more than 5MPa, while the effect of Poisson's ratio of rocks is very small;

  2. The value of stress shadow is determined by the shortest distance of fractures, which is more than 1.5 times fracture height when fracture length is longer than fracture height;

  3. The fractures between wells get close to each other with a deviation angle of more than 10° which can improve the stimulated reservoir volume far away from the wells;

  4. In certain reservoir conditions, the more higher slurry rate and the little the distance between the segmented clusters, the more strong stress shadow effect can be obtained.

More than 120 treatments have been performed with encouraging results 96% efficiency with an average post-fracturing rate reach to 22m3/d and saving more than 30% cost. Therefore, it has an important guide for multi-stage fracture geometry design.

1. Introduction

Over the past decade, multi-stage fractured horizontal wells have been widely applied to develop unconventional tight oil and gas resources, while hydraulic fracture stress interference is one of the critical factors influencing fracture propagation geometry. Therefore, it has a great value on optimization design and production forecast if investigating it profoundly. The first publication on the description of stress distribution in hydraulic fracturing operation goes back to 1946. Sneddon presented the stress distribution formula of plane linear hydraulic fracture based on the plane stress model of elastic mechanics and the complex variable function theory (Sneddon, 1946). In 1988, Warpinski and Teufel put forward a stress distribution formula of two-dimensional finite height linear fracture according to Sneddon formula (Warpinski and Teufel, 1988). The stress shadow of analytical solutions for the multi-stage fracturing was put forward by Fisher (Fisher, 2004).

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