Diverting fracturing stimulation using a novel diverting agent: Laboratory study and field application

A diverting fracturing technique has been widely utilized for old and new wells stimulation in various geothermal and petroleum fields, and has been paid much attention by governments and companies. Diverting agent is one of the key materials for this technology, and it is also one of the characteristics with which this technology is different from a conventional fracturing technology. Although some diverting agents have been developed, they have some shortcomings or are limited by application scenarios. Therefore, this paper introduced a novel thermo-responsive diverting agent and put forward a corresponding diverting fracturing process based on its characteristics. Through indoor and outdoor studies, positive findings were obtained. First, with the increasing temperature, the thermo-responsive diverting agent could realize a solution-gel-solution multiphase transition process. A change in the reservoir temperature during and after fracturing treatment could be utilized to realize the multiphase transition of this diverting agent. Second, the multiphase transition speed could be controlled by adjusting the gel factor (GF) dosage and heating temperature. Third, it had a good injection property (initial viscosity 3.7 mPa s) and could be quickly transformed into a semi-solid gel to achieve temporary blocking. Fourth, the breakthrough pressure of the semi-solid gel had a positive correlation with a plugging length, and the gradient was about 9.4 MPa/m. Fifth, it had good compatibility and low formation damage (only 2%), and could effectively protect the formation permeability. Finally, the results of fracturing construction curves, micro-seismic monitoring, and gas production data proved that this diverting agent had a promising outcome. The direction of formation break changed from the southwest to the northeast of the wellbore after temporary blocking confirmed by micro-seismic results. The production of diverting fracturing wells was 1.3 times that of the initial production and 1.5 times that of the later-stage production of conventional fracturing wells. This study provided a reference for the diverting fracturing stimulation in low permeability reservoirs.