According to one or more embodiments of the present disclosure, a drilling fluid may comprise one or more deep eutectic solvents in an amount greater than or equal to 70 wt. % based on the total weight of the drilling fluid. Each deep eutectic solvent may comprise at least one hydrogen bond acceptor compound and at least one hydrogen bond donor compound. A molar ratio of the total moles of the hydrogen bond donor compounds to the total moles of the hydrogen bond acceptor compounds in each deep eutectic solvent may be from 0.1 to 1.0. The drilling fluid may have a density greater than or equal to 200 kg/m.sup.3. The drilling fluid may have a viscosity greater than or equal to 0.5 Pa.Math.s when measured at 25° C. Methods for drilling wells in subterranean formations using the drilling fluid are also disclosed.

Rheology modifiers comprising dicarboxylic acid, additives and oil-based drilling fluids comprising said rheology modifiers, as well as methods and uses thereof are provided. The rheology modifier dicarboxylic acid may comprise, for example, dodecanedioic acid. Rheology modifiers as described herein may be used, for example, to increase low shear end viscosity of an oil-based drilling fluid.

The present invention relates to the well drilling field in petroleum industry, in particular to an additive composition suitable for viscosity reduction of oil-based drilling fluids, an oil-based drilling fluid and use thereof. The double-block copolymer mainly consists of a block A and a block B, wherein, the block A is composed of structural units represented by formula (1), the block B is composed of structural units represented by formula (2), and the number-average molecular weight of the block A is 1,500-10,000. The double-block copolymer provided in the present invention can be used as a viscosity reducer in oil-based drilling fluids, especially can be used as a viscosity reducer in high-density clay-free oil-based drilling fluids, and can greatly decrease the apparent viscosity and plastic viscosity of oil-based drilling fluids in high-temperature and high-pressure reservoir while maintaining appropriate shearing force, so as to increase the drilling rate and reduce drilling difficulties. ##STR00001##

The present invention relates to the well drilling field in petroleum industry, in particular to an additive composition suitable for viscosity reduction of oil-based drilling fluids, an oil-based drilling fluid and use thereof. The double-block copolymer mainly consists of a block A and a block B, wherein, the block A is composed of structural units represented by formula (1), the block B is composed of structural units represented by formula (2), and the number-average molecular weight of the block A is 1,500-10,000. The double-block copolymer provided in the present invention can be used as a viscosity reducer in oil-based drilling fluids, especially can be used as a viscosity reducer in high-density clay-free oil-based drilling fluids, and can greatly decrease the apparent viscosity and plastic viscosity of oil-based drilling fluids in high-temperature and high-pressure reservoir while maintaining appropriate shearing force, so as to increase the drilling rate and reduce drilling difficulties. ##STR00001##

This disclosure provides drilling fluids and additives as well as fracturing fluids and additives that contain cellulose nanofibers and/or cellulose nanocrystals. In some embodiments, hydrophobic nanocellulose is provided which can be incorporated into oil-based fluids and additives. These water-based or oil-based fluids and additives may further include lignosulfonates and other biomass-derived components. Also, these water-based or oil-based fluids and additives may further include enzymes. The drilling and fracturing fluids and additives described herein may be produced using the AVAP® process technology to produce a nanocellulose precursor, followed by low-energy refining to produce nanocellulose for incorporation into a variety of drilling and fracturing fluids and additives.

This disclosure provides drilling fluids and additives as well as fracturing fluids and additives that contain cellulose nanofibers and/or cellulose nanocrystals. In some embodiments, hydrophobic nanocellulose is provided which can be incorporated into oil-based fluids and additives. These water-based or oil-based fluids and additives may further include lignosulfonates and other biomass-derived components. Also, these water-based or oil-based fluids and additives may further include enzymes. The drilling and fracturing fluids and additives described herein may be produced using the AVAP® process technology to produce a nanocellulose precursor, followed by low-energy refining to produce nanocellulose for incorporation into a variety of drilling and fracturing fluids and additives.

A method and wellbore fluid using Curaua fiber to prevent or cure loss circulation during well operations. The wellbore fluid includes a base fluid and a plurality of Curaua fibers. The wellbore fluid may include concentration up to 120 lb/bbl Curaua fibers. The base fluid may include at least one of water-based fluid, brine-based fluid, oil-based fluid, synthetic-based fluid, or Pneumatic-drilling fluid system. The water-based fluids may further include at least one of seawater, brine, saturated brine, or formate brine. The water-based fluid may include a dispersed system. The water-based fluid may further include a non-dispersed system. The oil-based fluid may include at least one of diesel, mineral oil, and low-toxicity linear olefins and paraffins. The synthetic-based fluid may include at least one of one of esters, internal olefins and linear paraffins. The oil-based and the synthetic-based fluids may further include lime.

A method and wellbore fluid using Curaua fiber to prevent or cure loss circulation during well operations. The wellbore fluid includes a base fluid and a plurality of Curaua fibers. The wellbore fluid may include concentration up to 120 lb/bbl Curaua fibers. The base fluid may include at least one of water-based fluid, brine-based fluid, oil-based fluid, synthetic-based fluid, or Pneumatic-drilling fluid system. The water-based fluids may further include at least one of seawater, brine, saturated brine, or formate brine. The water-based fluid may include a dispersed system. The water-based fluid may further include a non-dispersed system. The oil-based fluid may include at least one of diesel, mineral oil, and low-toxicity linear olefins and paraffins. The synthetic-based fluid may include at least one of one of esters, internal olefins and linear paraffins. The oil-based and the synthetic-based fluids may further include lime.

Methods for reducing loss of wellbore fluid to formation may include pumping an oil-based wellbore fluid into the wellbore, where the wellbore includes an oleaginous continuous phase and a plurality of modified brine phases dispersed in the oleaginous continuous phase.

Methods for reducing loss of wellbore fluid to formation may include pumping an oil-based wellbore fluid into the wellbore, where the wellbore includes an oleaginous continuous phase and a plurality of modified brine phases dispersed in the oleaginous continuous phase.