Case Study

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Polymer-based completion fluids are the most commonly used fluids for completion fluid loss and reservoir protection. These fluids can achieve high viscosities with low fluid loss rates for a wide range of reservoir temperatures and permeabilities. However, one weakness of polymer-based fluids is the permeability damage that occurs as a result of incomplete polymer residue removal from the pores of the near wellbore matrix.

Over the past two decades, surfactant-based fluids have been developed for gravel packing, frac-packing, and conventional hydraulic fracturing. These surfactant micellar fluids have viscoelastic fluid properties created by the overlapping and entanglement of thread-like micelle structures in brines. Surfactant micellar fluids exhibit viscosity-dependant leak-off control, and do not form filtercake on porous media. This type of leak-off is often inefficient and results in a significant amount of whole gel leak-off into the formation. For this reason conventional surfactant micellar fluids can only be used successfully for reservoirs with permeabilities up to about 200 md.

This paper will introduce a new low-damaging fluid loss control system based on nanoparticle associated thread-like micelles. Presented are newly developed, select nano-size inorganic crystals with surface forces that uniquely associate or "pseudo-crosslink" overlapping thread-like micelles into a 3D network. This unique fluid system works in KCl, CaCl2, NaBr and CaBr2 completion brines with fluid mix weights up to 14.4 ppg. Lab data is presented that shows pseudocrosslinked thread-like micelle fluids have wall-building fluid loss control similar to crosslinked polymer fluids. The new nanoparticle-micelle association phenomena will allow surfactant-based fluids to be used for protecting reservoirs with permeabilities up to about 2500 md and temperatures up to about 300°F. Rheological tests are presented that show pseudo-crosslinked thread-like micelle fluids can achieve ultra-low shear rate viscosity above 1 million centipoise. Also introduced is micellar internal breaker technology, where the breaking agents preferentially reside within the thread-like micelle structures and will go wherever the micelles go for controlled and assured viscosity break. Core regain permeability data is also presented.