Nanomaterials-Enhanced Hydrocarbon-Based Well Treatment Fluids

Abstract

Abstract The introduction of water-based fracturing fluids to water-sensitive formations may cause formation damages and thereafter lower the production numbers. Due to the advantages such as low formation damage, good proppant suspending and carrying ability, good compatibility with water-sensitive formations, etc., the waterless, hydrocarbon-based fluids are routinely used in fracturing, sand control, coiled tubing cleanout, and other oilfield operations. To better generate fractures and place proppant, the phosphate esters-based gelled oil fluids have been preferred since they are more robust and cost-effective compared to other types of hydrocarbon-based fluids. Phosphate esters are commonly used with metal crosslinkers such as iron or aluminum compounds to form gelled oil fluids. Since phosphate esters may cause fouling in refinery equipment, the dosage should be reduced to the minimum but without compromising the fluid performance. A number of novel additives have been identified that could maintain or even enhance the rheological properties of the gelled hydrocarbon fluids with reduced usage of the phosphate esters. When doped with the novel functional nanomaterials, the rheological properties of the gelled hydrocarbon-based fluids were enhanced from room temperature to 250°F or above. The selected nanomaterials could have van der Waals-like forces, thus strengthening the three-dimensional network of the metal-crosslinked phosphate esters in the gelled hydrocarbon fluid. This way, the overall viscosity of the hydrocarbon-based fluid could increase with lower amount of phosphate esters. For example, the addition of 30ppt (pounds per thousand gallons) of additive-A synergistically improved the viscosity of the gelled oil fluid by about 73% compared to the baseline gelled fluid that did not contain the additive. With additive-A at 30ppt, the amount of the phosphate esters in the fluid could be reduced by 25% without affecting the fluid performance. Besides additive-A, other types of functional nanomaterials including additive-B, additive-C, and additive-D were all found to enhance the rheological properties of the gelled hydrocarbon fluids by as much as about 45%. The novel gelled hydrocarbon fluid formulas were successfully applied with the crude oil from the field, resulting in viscosity boosts up to about six times. Further discussions about the enhancing behaviors and mechanisms of the selected novel additives in the gelled hydrocarbon fluids and the laboratory test results will be presented in detail.