Abstract

In the paper, a three dimensional fracture propagation model was first established, then the factors that affect the fracture vertical growth were analyzed by means of the fracturing design software from the model. It is shown that although many factors influence the fracture height growth, the most important one is the minimum in-situ stress contrast between payzone and bounding zones. The pump rate and rheologic parameters for fracturing fluid also affect the height propagation to some extent. By analyzing the three dimensional fracture propagation model, we found that it is the stress intensity factors on the tips of line crack that have a direct influence on the height growth. Consequently, even though it is not easy to increase the in-situ stress contrast, we can manage to change the vertical distribution of flowing pressure in the fracture by adding some buoyant and sedimentary material to pad fluid, forming two artificial barriers at the top and bottom of the fracture. The two barriers decrease the flowing pressure in the fracture located at bounding zones, which is equivalent to the increase in in-situ stress contrast. Up to now, 13 wells have been fractured by optimizing treatment parameters and adding barrier material. All the wells had a great increase in oil production, and the fracture height inferred from well temperature logging is close to the perforated interval.

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