In Situ Synthesization of Porous Polyurethane for Particle Filtration and Fracture Support: Implications to Gas Production from Unconsolidated Formations

Gas production from unconsolidated formations is often challenged by sand production and low reservoir permeability. All past 11 field trials of gas production from hydrate reservoirs encountered various degrees of sand production, with five of them suspended due to severe sand production. This study investigates the potential of synthesizing open-cell polyurethane (PU) as a sand control filter and hydraulic fracturing proppant in water-saturated clayey sediments. The results show that the properties of formed polyurethane are heavily affected by constituent proportions, additives (e.g., catalyst and surfactant), the mixing sequence, and the hardening time. Simultaneous injection of catalyst and a premix (of toluene diisocyanate TDI, 1,4-butanediol BDO, and surfactant) into water can form polyurethane with consistent final volumes and correspondingly stable engineering properties. The stiffness and strength of polyurethane increase rapidly during the first 48 h of hardening and then stabilize at an unconfined compressive strength of UCS = ∼1 MPa. The morphology of formed polyurethane, which is in localized chunks around the injection port as sand filters or in planar fractures propagating over a greater distance as proppants, can be manipulated by the injection flux, the amount of catalyst, and in situ effective stresses. This technique of using in situ synthesis of open-cell polyurethane, forming fracture proppants reaching the far field, followed by chunk-like filters around the injection ports, provides a novel solution for sustainable and efficient hydrocarbon recovery from unconsolidated sediments.