A High Efficiency Low Damage Fracturing Fluid for Deep Coalbed Methane Development

In developing deep coalbed methane (CBM), existing fracturing fluids have deficiencies such as poor sand carrying capacity and high core damage. To overcome these deficiencies, a fracturing fluid system (HMP/OP) was developed with a main fracturing fluid agent designed and developed based on principles of supramolecular polymer chemistry. This main agent is used for deep CBM production and is physically crosslinked with surfactants to formulate the HMP/OP fracturing fluid with high sand carrying capacity and low formation damage. Laboratory experiments on its drag reducing performance, sand carry capacity, gel breaking capacity, core damage potential as well as adsorption/desorption capacity show that HMP/OP can significantly reduce flow drag (by 73%). At 100℃ and 20% sand content, the time for the sand to be suspended by the HMP/OP fracturing fluid is 110 min, and the settling rate of sand is 0.8 cm/min. At 80℃, after gel breaking for 2 hours, the viscosity and the residue content of the fluid are 4.63 mPa·s and 353.12 mg/L, respectively. The percent core damage caused by the HMP/OP fluid after gel breaking is only 17.44%. Moreover, the adsorption capacity of HMP/OP on the surfaces of coal rocks is only 0.32 mg/g. Adding 0.2% desorption agent (SH-12) into the HMP/OP fluid, 1.72 mL/g methane can be separated from the fluid after gel breaking. The fracturing fluid HMP/OP, developed through physical crosslinking, possesses high sand ratio, low formation damage, low adsorption capacity and enhanced methane desorption capacities, satisfying the engineering technical requirements of efficient development of coalbed methane.