Limited entry is the process of limiting the number or reducing the entry-hole diameter of perforations in such a way that significant perforation friction pressure is achieved during the treatment. Perforation friction establishes a backpressure in the wellbore that tends to allocate flow among the multiple perforation intervals/clusters, thus improving control of the hydraulic fracturing process. In horizontal wells, limited entry is often used in conjunction with the Plug-and-Perf process and is one of the most economical processes available to stimulate wells completed in unconventional reservoirs. To implement effective limited entry treatments, it is important to understand the mechanisms impacting pressure drop across perforations and use that knowledge to take appropriate precautions when designing and implementing the treatment. This includes identifying or predicting variations in mechanical rock properties such as stress within the reservoir.
This presentation introduces critical considerations in executing limited entry treatments and develops key concepts through the use of case studies.