Coal-bed hydraulic fracturing is a key process in coal-bed gas production and one of the important ways for improving its efficiency is to make a new kind of proppant. What is important here is to reduce its density as much as possible, maintaining its technical parameters including strength.
Activated water often used as a fracturing liquid in hydraulic fracturing of coal seam is favourable for forming a complex fracture net, with stable performance and low frictional resistance, but it is limited in hydraulic fracturing due to its low viscosity and low capacity of carrying proppants. The use of ultra-low density proppants for hydraulic fracturing can solve problems such as clogging of cracked pores after gel break of the fracturing liquid and low productivity, often encountered in hydraulic fracturing using dense sand or ceramic granular proppants, and can provide sufficient proppant carrying capacity by crystalloid solutions such as clean and cheap activated water.
In order to solve the problems of high settling rate of proppants when low-cost activated water is used as a hydraulic fracturing liquid, Yun Myong Guk, a researcher at the Faculty of Earth Science and Technology, has prepared a resin-coated ultra-low density proppant with solid slag and white fly ash as feedstock.
He has analyzed the effects of the material composition and the resin dip and coating of the proppant on its performance by X-ray diffraction (XRD), mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM) and cylinder pressure methods.
The analysis results are as follows.
The packing effect was best when resin concentration was 25wt.%. When the coating resin content of the proppant dip body was 6%, the visible porosity of particles was reduced to 7.13% and its bulk density was 0.91g/cm3. The apparent density was 1.5g/cm3 and the acid solubility was 0.35%. The breakage rates were 7.3% and 9.0%, respectively under 16MPa and 20MPa closing pressure conditions.