H. Shirazi - PhD. candidate, Mining, Faculty of Mining, Petroleum and Geophysics, Shahrood University of Technology
S.R. Torabi - Professor, Faculty of Mining, Petroleum and Geophysics, Shahrood University of Technology
F. Sereshki - Assoc. Professor, Faculty of Mining, Petroleum and Geophysics, Shahrood University of Technology
H. Mirzaei - Assist. Professor, Faculty of Mining, Petroleum and Geophysics, Shahrood University of Technology

Hydraulic fracturing, in comparison with other existing methods, is an easy, quick and simple approach to measure in-situ stresses. This method is used to determine the magnitude and direction of maximum and minimum horizontal stresses in deep or shallow drill holes which is normally not possible by other methods. It originated in the 1940s to stimulate the oil production by fracturing and extending the existing cracks in the ambient rock mass. It was in 1964 which this method was used to determine the field stress for the first time. In this method, in order to increase the fluid pressure in the wellbore to fracture the rock mass, two packers are employed in a fixed interval in the depth under question. Evaluation of the impact of distance between the packers on fracture pressure (breakdown pressure) in this procedure, was the subject of this study. In this respect a laboratory physical model was designed and constructed and a significant number of tests were conducted. The results showed that by increasing the ratio of the length to the diameter of the interval the breakdown pressure decreases.

Hydraulic Fracturing, Packer intervals, Fracture Pressure