Experimental near-wellbore hydraulic fracture initiation and growth for horizontal wells with in-plane perforations

To understand the fracture behavior during different perforation modes on horizontal wells, laboratory-scale hydraulic fracturing experiments with acoustic emission monitoring were conducted on tight concrete samples. The experimental results indicated that the breakdown pressure could be greatly reduced and that a simple fan-like structure was created with in-plane perforations on a horizontal well under the same fracturing treatment conditions. Furthermore, there was a positive relationship between treatment parameters and breakdown pressure for helical perforations. Because of the small pressurization rate and large stress interaction, the breakdown pressure with in-plane perforations is smaller than that of helical perforations. However, the treatment parameters were not sensitive to the breakdown pressure but correlated with the shut-in pressure for the in plane perforation mode. In general, increasing the pump rate and fracturing fluid viscosity can slightly increase the breakdown pressure and substantially increase the shut-in pressure. The increase in fracture extension pressure in the in-plane perforation mode refers to different fracture initiation orders of individual perforations. Although the deviation and failure of fracture initiation of some perforations can be observed due to the strong stress interaction of in-plane perforations, the existence of perforation tunnels can guide hydraulic fracture propagation within one plane. Thus, hydraulic fractures can connect and create large-scale fractures because of the close perforation spacing. The results of trace length and microscale fracture demonstrate that twisted and curved fractures with smaller widths can be significantly created by the helical perforation mode, but large-scale fractures can be created by the in-plane perforation mode, which is beneficial to sand plugging mitigation.

Automated summary

Different fracture behaviors were studied in laboratory-scale hydraulic fracturing experiments on tight concrete samples with acoustic emission monitoring. The results showed that in-plane perforations can greatly reduce the breakdown pressure and create a simple fan-like structure, while helical perforations had a positive relationship between treatment parameters and breakdown pressure.