A New Water Soluble Temporary Plugging Agent and its Temporary Plugging and Diverting Effects in Re-fracturing

Re-fracturing of an oil well is one of the important methods of restoring its production capacity and enhancing its ultimate recovery. The most effective re-fracturing method presently in use is to fracture the reservoir formations with fracturing fluid containing temporary plugging agent functioned as diverting agent. An environmentally friendly water soluble temporary plugging diverting agent has recently been developed with biodegradable materials, high molecular weight polymers, an expansion agent and a solidifying agent. The particle sizes of this temporary plugging agent can be customized to fit for the width of fractures into which the particles will go in. The temporary plugging agent dissolved 4 hours after the fracturing operations. Laboratory experiments on cores indicated that 99% of the pores in the cores can be plugged by this plugging agent, with pressure bearing capacity of at least 40 MPa. The dissolved plugging agent had only minor impairment to the permeability of cores, meaning that the temporary plugging agent had satisfied the needs of fracturing job. On field trial on a well, after adding the temporary plugging agent, operating pressure went up to 3 MPa, proving that the temporary plugging agent functioned very well. Daily oil production rate of the fractured well was increased by 1.1 t, and water cut of the well was reduced by 5%, indicating that the use of this fracturing method has realized the goal of restoring production capacity and reducing water cut.