Rheological Properties of BCG-CO₂ Fracturing Fluid for Shale Gas

BCG-CO₂ fracturing fluid system is especially suitable for shale gas stimulation with advantage of minimizing the actual water consumption, reducing the damage to formation, recovering more rapidly and efficiently, etc. A major objective of this article is to ascertain the rheological properties of BCG-CO₂ fracturing fluid in a wide range of experimental conditions for guiding the selection of fracturing parameters. The experimental results showed that as the temperature reaches 35 °C, the effective viscosity of BCG-CO₂ fracturing fluid has an obvious increase. Apparently the shear rate change below 1000 s^-1 is sharper than that above 1000 s^-1. The effective viscosity presents an increase trend with increasing foam quality under foamed conditions. It has been concluded that the key factors influencing rheological characteristics of BCG-CO₂ fracturing fluid are both temperature and foam quality, and the exponential function form can be used to describe the change rule approximately.