Question

In hydraulic fracturing design, what is the physical relationship between the net pressure in the fracture and the fracture width as the fluid viscosity increases?

Accepted Answer

In hydraulic fracturing, the net pressure is defined as the difference between the fluid pressure inside the fracture and the minimum in-situ stress of the rock formation. The fracture width is the physical gap created when fluid is pumped into the rock. As the viscosity of the fracturing fluid increases—meaning the fluid becomes thicker and more resistant to flow—the energy required to move that fluid through the narrow fracture space also increases. This heightened resistance creates a greater pressure drop along the length of the fracture, which requires higher injection pressures to keep the fluid moving. Consequently, higher fluid viscosity leads to higher net pressure within the fracture. Because the rock walls must deform to accommodate this increased internal pressure, the physical width of the fracture increases. Therefore, there is a direct positive relationship: increasing the fluid viscosity increases the net pressure, which in turn results in a wider fracture.

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In hydraulic fracturing design, what is the physical relationship between the net pressure in the fracture and the fracture width as the fluid viscosity increases?