Particles in Oil for Viscoelastic Surfactant Gelled Fluids
Fluids viscosified with viscoelastic surfactants (VESs) may have their fluid loss properties improved with the presence of at least one mineral oil in combination with at least one particulate fluid loss control agent that may be an alkaline earth metal oxides, alkaline earth metal hydroxides, transition metal oxides, transition metal hydroxides, and mixtures thereof. The mineral oil may initially be dispersed oil droplets in an internal, discontinuous phase of the fluid. In one non-limiting embodiment, the mineral oil is added to the fluid after it has been substantially gelled. The particulate fluid loss control agent may be added in any order relative to the VES and the mineral oil fluid loss control agent. The mineral oil may enhance the ability of a particulate fluid loss control agent to reduce fluid loss. The presence of the mineral oil may also eventually reduce the viscosity of the VES-gelled aqueous fluid.
1 . An aqueous fluid comprising:
water;
at least one viscoelastic surfactant (VES) in an amount effective to increase the viscosity of the aqueous fluid;
at least one particulate fluid loss control agent slurried in at least one mineral oil fluid loss control agent in an amount effective to reduce fluid loss of the aqueous fluid, where the at least one mineral oil fluid loss control agent has a dynamic viscosity greater than 20 cps at ambient temperature, and where the at least one particulate fluid loss control agent is present in an amount effective to reduce fluid loss of the aqueous fluid, where the at least one particulate fluid loss control agent is selected from the group consisting of alkaline earth metal oxides, alkaline earth metal hydroxides, transition metal oxides, transition metal hydroxides, and mixtures thereof, where the at least one particulate fluid loss control agent has a particle size equal to or less than about 0.2 millimeter,
where the fluid loss control agents are present in amounts effective to synergistically reduce the viscosity of the gelled aqueous fluid as compared to using the mineral oil fluid loss control agent or the particulate fluid loss control agents independently.
2 . The aqueous fluid of claim 1 where the at least one mineral oil fluid loss control agent is at least about 99 wt % paraffin.
3 . The aqueous fluid of claim 1 where the at least one mineral oil fluid loss control agent has a distillation temperature above about 300° C.
4 . The aqueous fluid of claim 1 where the effective amount of the at least one mineral oil fluid loss control agent ranges from about 0.2 to about 10% by based on the total fluid.
5 . The aqueous fluid of claim 1 where the effective amount of the at least one particulate fluid loss control agent ranges from about 0.0001 to about 200 pptg (from about 0.01 g/m 3 to about 24 kg/m 3 ).
6 . An aqueous fluid comprising:
water;
at least one viscoelastic surfactant (VES) in an amount effective to increase the viscosity of the aqueous fluid;
from about 0.0001 to about 200 pptg (from about 0.01 g/m 3 to about 24 kg/m 3 ) based on the total fluid of at least one particulate fluid loss control agent slurried in from about 0.2 to about 10% by based on the total fluid of at least one mineral oil fluid loss control agent, and where the at least one mineral oil fluid loss control agent has a dynamic viscosity greater than 20 cps at ambient temperature, and where the at least one particulate fluid loss control agent is selected from the group consisting of alkaline earth metal oxides, alkaline earth metal hydroxides, transition metal oxides, transition metal hydroxides, and mixtures thereof, where the at least one particulate fluid loss control agent has a particle size equal to or less than about 0.2 millimeter,
where the fluid loss control agents are present in amounts effective to synergistically reduce the viscosity of the gelled aqueous fluid as compared to using the mineral oil fluid loss control agent or the particulate fluid loss control agents independently
7 . The aqueous fluid of claim 6 where the at least one mineral oil fluid loss control agent is at least about 99 wt % paraffin.
8 . The aqueous fluid of claim 6 where the at least one mineral oil fluid loss control agent has a distillation temperature above about 300° C.
9 . An aqueous fluid comprising:
water;
at least one viscoelastic surfactant (VES) in an amount effective to increase the viscosity of the aqueous fluid;
from about 0.0001 to about 200 pptg (from about 0.01 g/m 3 to about 24 kg/m 3 ) based on the total fluid of at least one particulate fluid loss control agent slurried in from about 0.2 to about 10% by based on the total fluid of at least one mineral oil fluid loss control agent, and where the at least one mineral oil fluid loss control agent has a dynamic viscosity greater than 20 cps at ambient temperature is at least about 99 wt % paraffin, and has a distillation temperature above about 300° C., and where the at least one particulate fluid loss control agent is selected from the group consisting of alkaline earth metal oxides, alkaline earth metal hydroxides, transition metal oxides, transition metal hydroxides, and mixtures thereof, where the at least one particulate fluid loss control agent has a particle size equal to or less than about 0.2 millimeter,
where the fluid loss control agents are present in amounts effective to synergistically reduce the viscosity of the gelled aqueous fluid as compared to using the mineral oil fluid loss control agent or the particulate fluid loss control agents independently.