This case history paper describes a technique that minimizes the creation of multiple fractures in deep coal seams during hydraulic fracturing operations. The technique enabled the operator and the service company to perform 24 nitrogen foam-fluid fracturing treatments in 33 days in the Upper Silesian basin (Poland).
The creation of multiple fractures is a phenomenon often encountered during fracturing operations in coal seams and is the most probable cause of early screenouts. During this fracturing campaign, early screenouts were observed at sand concentrations less than 3 lb/gal. These screenouts were attributed to a lack of fracture width caused by the presence of multiple fractures, including possible horizontal fracture components or tortuosity.
The operator and the service company developed a technique that involves pumping a small volume of highly viscous crosslinked gel before the main fracturing treatment. This technique prevented early screenouts and allowed the higher sand concentrations to be pumped.