Study on the frictional pressure drop of borate-crosslinked N₂ foam fracturing fluid

Borate-crosslinked N₂ foam fracturing fluid presents the property of non-Newtonian fluid, and the characteristics of its frictional pressure drop in vertical oil pipe under the conditions of actual fracturing operation directly affects the accurate estimations of fracturing pressure and fracturing result. The characteristics of the frictional pressure drop of borate-crosslinked N₂ foam fracturing fluid in vertical pipe are experimentally studied under the condition of the simulated practical fracturing operation of 15∼45 MPa and 50∼110°C. It is shown that, the frictional pressure drop gradient of the fracturing fluid increases with the increase of its flow velocity, decreases with the increase of temperature and increases with the increase of pressure. The frictional resistance factor increases with the increase of the flow velocity, decreases with the increase of temperature and its variation law with the pressure is complicated. The relational expression between the frictional resistance factor and generalized Reynolds number is obtained by the experiments, and whose average calculation error is 10.2% under the experimental condition.