Wet microbubble foams (WMF) are of growing interest in various oilfield applications: drilling, completions, water flood monitoring, hydraulic fracturing etc. The most attractive properties of WFMs therein are their low density, high yield-stress rheology as well as their pressure-triggered mobility in porous media. The main complication in the development of a successful oilfield technology lies in the development of WMFs able to survive reservoir pressure and temperature. In respect to such severe environment unique are the properties of the WMFs known as colloidal gas aphrons (CGAs). CGA based fluids consist of microbubbles, the cores of which are composed of a gas surrounded by a thick multilayer surfactant film. Wettability tests show that CGA bubbles have very little affinity for each other or for the mineral surfaces of rock formations.
In the work a procedure for the preparation of monodisperse CGA stable at reservoir pressure is developed. It is based on the modeling of foaming process in gas-oversaturated solution. A set of experiments is conducted in order to validate the model and determine the key factors affecting the properties of the final CGAs.
The behavior of CGA based fluids under pressure variations is studied experimentally by optical microscopy. A high-pressure thermostabilized optical cell is specially designed for use with Carl Zeiss inverted microscope to visualize CGA microbubbles at pressure up to 40 MPa. The CGA images taken with the microscope camera are processed in order to calculate bubble size distribution (BSD).
The CGAs studied are prepared with anionic surfactants sodium dodecyl sulfate and potassium stearate as aphronizers and xanthane gum as polymer viscosifier. The results show that the aprons produced by our method have narrow BSD remaining in other respects common CGAs. The dependence of the final BSD on the gas oversaturation and the pressure release rate are examined in detail.
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