Foaming supramolecular surfactants for gas mobility control in naturally fractured carbonate reservoirs at high temperature, salinity, and hardness

Oil production and maintenance are essential issues in naturally fractured reservoirs because they are the largest and most productive on earth. However, they present early water and gas channeling but could be remediated by using foaming agents to control these phenomena through blocking channeling areas. In Mexico these reservoirs have pressure up to 5,500 psi, high temperature up to 200 °C, salinity up to 400,000 ppm, and hardness up to 250,000 ppm; due to these thermodynamic conditions, there has been no available technology to form stable enough foams. In this work, a foaming supramolecular surfactant with the capability to chelate Ca²⁺ ions is examined. As a result, surfactant monomers are bridged by captured Ca²⁺ cations leading to the formation of high-molecular-weight oligomers, which significantly increment the viscosity of the solution improving the foam stability, and since at this manner the Ca²⁺ cations are no longer available to precipitate as components of solid salts, the foaming supramolecular surfactant also performs as antiscalant. These observations are explained through quantum theoretical modeling. The foam is stable, effectively blocking the gas channels, whereas in presence of oil the foam is broken leading the oil to pass into the wellbore. The characteristic rheological properties of the foam allow its injection into the formation at a range of flow rates, foam qualities, and shear stress to achieve the flooding and the blocking of a variety of fractured carbonate formations, and the change of the wettability of the matrix, which is a desirable behavior in a huff and puff process, as reported in a previous publication about a successful pilot test of this foam.