Hydraulic Fracturing Research And Numerical Simulation Of The Set Surface Perforation In Horizontal Well

The technology of the set surface perforation in horizontal well is a kind of new-fashioned perforating technology. Horizontal well can avoid penetrating complex terrain by changing the azimuth of oil layer, thus reducing the difficulty of implementation. The technology of set surface perforation can gain optimal fracture surface, expand crack area reduce the rock breaking pressure and guide the trend of crack scientifically by adjusting the distribution of perforating bullet.Comparing with conventional perforation and single perforation. The set surface perforation can reduce the crack pressure of rock, increase the crack area of rock, reduce the destruction of the formation, increased stability of the rock and increase oil production. This paper use the principle of maximum tensile stress and combine with numerical simulation method to conduct research on hydraulic fracturing and rock fracture of set surface perforation in horizontal well.This papaper mainly from the following aspects of research and analysis:Firstly, In this paper, by studied the different ground stress, perforation angle (15°, 30°, 45°,60°, 75°, 90°), perforation size (perforation diameter, perforation depth), Predicting crack area (1.the same angle, different fracturing fluid pressure; 2. the same fracturing fluid pressure) and so on,we find the variation law of rock cracking pressure in different influencing factors. Obtained by simulation: (1) Under different ground stress states, the rock breaking pressures are different.Under the condition of normal fault, the maximum cracking pressure is needed. Then is the strike slip fault, and under the condition of reverse fault, the minimum cracking pressure is required.The variation of the maximum horizontal principal stress and the minimum horizontal principal stress has an effect on the rock cracking pressure. (2) Under the same ground stress condition, the same results are obtained from three kinds of ground stress states. The cracking pressure of rock increases with the increase of perforation angle. (3) When the perforation diameter increases, the cracking pressure shows a decreasing trend. (4) Under the condition of the same fracturing fluid pressure, changing the angle between perforation, when the perforation angle is 60 degrees, the crack propagation area, perforation interval and adjacent perforation crack propagation regionare the most suitable, the final track propagation region is maximal, then is when the angle is 45 degrees. Under the condition of the same perforation angle, because of the increase of fracturing fluid pressure, the stress interacts between different perforations, and the crack occurs at the junction between the perforation and the wellbore, then the interpenetration is occurred. Finally the fan-shaped predicted fracture surface is formed.Secondly, the three types of perforating projectiles are analyzed from the following two aspects: the initiation pressure of rock and the prediction of crack area. The three types of perforating bullets are 1# perforating bullet(aperture 10.4mm, hole depth 660mm), 2# perforating bullet (aperture 11mm , hole depth 876mm), and 3# perforating bullet(aperture 16.9mm, hole depth 646mm). The optimal 2# perforating bullet type is obtained.Finally, the author use finite element software to establish a simple comparative analysis of single perforation, conventional perforation and the set surface perforation:(1) Compare the cracking pressure of rock under different perforation modes: about single perforation, mainly studied the rock breaking pressure when the angle is changed from 0 degrees to 90 degrees;conventional perforation: Only to study the situation that the perforation spacing along the Y axis is 6cm/24cm/6cm. (2) the three kinds of perforation are compared under the same fracturing fluid pressure (40MPa, 60MPa) and carry on the comparison of predicted crack area. Results show:compared with the first two perforating methods, the set surface perforation has some advantages in both reducing the crack pressure and predicting the crack area.From above analysis, in this paper, the research about how to reduce the crack pressure is carried on and mainly studied the variation law of rock crack pressure under different influencing factors, thus, the optimization of the perforation is carried out.