In the Gulf of Mexico, momentum is increasing for drilling and completing wells deeper than 25,000 ft and with bottomhole pressures exceeding 20,000 psi. High-density base fluids have become standard components of fracturing or frac-pack completions to achieve working pressures below 15,000 psi at surface due to equipment limitation. Stimulation designs for these deep, high-profile wells aim to achieve long fracture lengths using large treatment volumes. Cleanup and maximum recovery of the high-density fracturing fluid is a necessity to maximize the effective fracture length, and thereby the production potential after these treatments.

Interfacial tension, contact angle and wettability are the key parameters to consider when choosing a surfactant package for maximizing fluid recovery. Historically, the surfactant packages that have been used in conventional fracturing fluids generally focused on water-wetting or non-wetting and lower surface tension results.

This paper presents details of laboratory studies to optimize a surfactant package for high-density base fluids. Fluid recovery studies were done on a sand column along with the measurement of the contact angle and interfacial tension of high-density base fluid with various surfactants. Core flow tests were also performed to evaluate regain permeability and cleanup. The tests with optimized surfactant package resulted in more than 90% regain permeability with a high-density fracturing fluid system and correspond with the results from the fluid recovery sand column testing. Laboratory tests show that the synergetic effects of interfacial tension, contact angle and wettability together are more significant than any one individual parameter and that more surfactant is not always better.

Selecting and optimizing a suitable and compatible surfactant package enhances the recovery and cleanup of a high-density fracturing fluid, which can result in highly conductive and longer effective fracture lengths.

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