Experimental study on the discharge coefficient of perforation behaviours during hydraulic fracturing treatments

Abstract

Hydraulic fracturing treatments are a significant stimulation technique for unconventional oil and gas reservoirs. The limited-entry technique is one of the most commonly used techniques for fluid diversion during hydraulic fracturing. This technique depends on the perforation pressure drop to achieve uniform injection profiles. The perforation pressure drop is influenced by many factors, such as flow rate, proppant concentration and fluid viscosity. The discharge coefficient (C_d) can also affect the perforation pressure drop. This research provides an understanding into the influence of various factors on the discharge coefficient. Perforation hole size, perforation plate thickness, perforation hole geometry, downstream restriction, friction reducer, fluid viscosity and horizontal behaviors are investigated in this work. The experimental results show that the perforation hole size does not impact the discharge coefficient; and that the perforation plate thickness, friction reducer fluid loading and fluid viscosity have a positive relation with the discharge coefficient value. For different perforation hole geometries, a smooth and tapered edge hole has a larger Cd value than the same shaped sharp-edge hole. When a downstream restriction is installed, the Cd value increases when the distance between the downstream reflection plate and the perforated plate increases. For the horizontal well behaviors, the Cd value of perforated horizontal casing is a little higher than the C_d of perforated plate. Overall, this study on the effect of influencing factors on the perforation Cd value help form a better understanding of perforation pressure drop behaviors and can improve the design of limited-entry techniques.