Experimental study of investigating effect of crack geometry in well wall on hydraulic fracturing pressure

The term hydraulic fracturing expresses process of beginning and expanding the crack in the rock that caused by hydraulic pressure exerted by the fluid which is a way for assessing state of tensions in the ground and increase the efficiency of oil reservoirs. In this study, by carring out laboratory test, the effect of the geometry of cracking created in the wall of the well is investigated on hydraulic fracture pressure. This investigation is important because the companies that perform the hydraulic fracture are always trying to decrease cost of pump purchase. So pressure investigation can be useful in selecting suitable pump. For testing, a series cylindrical and hollow samples with a 73 mm external diameter, 25 mm inner diameter and 150 mm height are provided. In these samples, artificial cracks were created and the effect of length, height and crack thickness on hydraulic pressure was investigated. These tests are carried out for several different modes that in each series one of the parameters is changed and two other parameters are fixed and the effect of each parameters on the hydraulic fracture pressure is investigated. For the production of cylindrical samples, a mold was made to prepare cracked sample. The experimental results indicate that hydralic fracturing pressure linearly decreases with a increasing in the length and height of the crack. This pressure nonlinearly decreases with a increasing in the crack width. Also, crack length have more effect than crack height on the hydraulic fracture pressure and is also greater than the crack width.