The use of foamed fluids has become popular in coal and shale reservoirs due to their inherent non-damaging properties. Foam is generally considered to be a perfect transport fluid. However, the proppant transport properties have not been fully measured in the laboratory. This paper discusses the design and construction of equipment to generate stabile foams in the laboratory and in the field, as well as the measurement of proppant transport and cleanup of foams commonly pumped into shallow, water sensitive reservoirs.

The equipment assembled for measuring proppant transport of foamed fluids includes a high pressure slurry pumping system, a choke system to generate field quality foams, a pipe rheometer to obtain in-line pipe rheology, a high pressure, see-through slot with remote video to observe proppant transport and a pressure control and exhaust system. Other equipment used includes a conventional sand column generator and core flow equipment to look at the impact of foam on coal permeability.

Several tests have been completed including the optimization of mixing tube diameter and velocity to achieve a stabile foam in the laboratory and in the field.

The impact of gel concentration and surfactant concentration on foam stability is measured to achieve minimum stability and maximum cleanup. Various surfactants are evaluated for cleanup. Their ability to avoid foam regeneration or blockage during flowback is also evaluated. Finally, the rheology, transport properties and half-lives of foams with and without sand are examined.

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