Movement of Hydraulic Fracturing Sand

Abstract

Hydraulic fracturing makes the very permeable channel, where the fracture is created in the reservoir formation by the injection of fluid suspending sand with high pressure and high rate and then the openning of fracture is filled up with sand carried in the fracturing fluid, for the purpose of elevating the productivity or flowing capacity of oil reservoir. Therefore, the study on the movement of sand during the fracturing procedure, especially transportation and deposition of sand in the fracture openning, is thought to be very useful for understanding of fracturing process and promoting its effectiveness.This paper states, first, the experimental and theoretical studies on the precipitation of sand grains in the non-flowing fluid and experiment of sand movement in the flowing fluid in the fracture openning, which is represented by the model apparatus. The sand mixed in the flowing fluid precipitates and deposits to the bottom of channel because of gravity segregation, when the flow rate is low. But when the flow rate reaches to the certain degree, the equilibrium is obtained such as no more precipitation of sand occures nor the previously deposited sand moves. The velocity of this state is defined as equilibrium velocity. This paper reveals the equilibrium velocities, which are obtained experimentally for sands in water, medium weight crude oil and the gel fluid and discussion about movement and deposition of sand in the fracture openning by application of those data. Furthermore, a few points, which should be considered carefully at the fracturing practices, are induced.