A repairing assembly includes a housing, a packer, and a thermal spray assembly. The housing is attached to a wellbore string disposed within a wellbore with casing. The packer is coupled to the housing. The packer is set on a wall of the wellbore to bound a repair zone defined between the packer and an end of the housing opposite the packer. The housing or the packer includes a fluid channel in fluid communication with the wellbore string or an annulus of the wellbore. The thermal spray assembly is coupled to the housing and sprays a damaged section of the casing with a thermal spray to repair the damaged section. The housing flows an inert gas received from the wellbore string or the annulus of the wellbore and through the fluid channel into the repair zone until an oxygen in the repair zone is substantially removed from the repair zone.

A repairing assembly includes a housing, a packer, and a thermal spray assembly. The housing is attached to a wellbore string disposed within a wellbore with casing. The packer is coupled to the housing. The packer is set on a wall of the wellbore to bound a repair zone defined between the packer and an end of the housing opposite the packer. The housing or the packer includes a fluid channel in fluid communication with the wellbore string or an annulus of the wellbore. The thermal spray assembly is coupled to the housing and sprays a damaged section of the casing with a thermal spray to repair the damaged section. The housing flows an inert gas received from the wellbore string or the annulus of the wellbore and through the fluid channel into the repair zone until an oxygen in the repair zone is substantially removed from the repair zone.

An apparatus for continuously generating and controlling the density of foam has a fluid in-flow manifold in communication with a source of liquid and comprising a pressure sensor. A plurality of branch lines are in fluid communication with the in-flow manifold a foam out-flow manifold. Each branch line has a flow control valve, a Venturi tube and in fluid communication with a throat of each Venturi tube an air induction control valve. The foam out-flow manifold has a pressure sensor. At least one in-flow control valve is disposed between the source and the in-flow manifold and at least one out-flow control valve is in communication with the out-flow manifold. The branch valves, air valves, the in-flow control valve and the out-flow control valve are operable to provide a chosen flow rate of the liquid and a selected foam product flow rate at a selected density of the foam product.

An apparatus for continuously generating and controlling the density of foam has a fluid in-flow manifold in communication with a source of liquid and comprising a pressure sensor. A plurality of branch lines are in fluid communication with the in-flow manifold a foam out-flow manifold. Each branch line has a flow control valve, a Venturi tube and in fluid communication with a throat of each Venturi tube an air induction control valve. The foam out-flow manifold has a pressure sensor. At least one in-flow control valve is disposed between the source and the in-flow manifold and at least one out-flow control valve is in communication with the out-flow manifold. The branch valves, air valves, the in-flow control valve and the out-flow control valve are operable to provide a chosen flow rate of the liquid and a selected foam product flow rate at a selected density of the foam product.

A method of preparing and a composition of an oil-based drilling fluid. An oil-based drilling fluid includes a base oil continuous phase, in which the base oil continuous phase includes a base oil, an aqueous dispersed phase, and at least one rheology modifier comprising a modified magnesium/aluminum carbonate layered-double hydroxide (Mg/Al—CO.sub.3 LDH) compound.

A method of preparing and a composition of an oil-based drilling fluid. An oil-based drilling fluid includes a base oil continuous phase, in which the base oil continuous phase includes a base oil, an aqueous dispersed phase, and at least one rheology modifier comprising a modified magnesium/aluminum carbonate layered-double hydroxide (Mg/Al—CO.sub.3 LDH) compound.

A repairing assembly includes a housing, a packer, and a thermal spray assembly. The housing is attached to a wellbore string disposed within a wellbore with casing. The packer is coupled to the housing. The packer is set on a wall of the wellbore to bound a repair zone defined between the packer and an end of the housing opposite the packer. The housing or the packer includes a fluid channel in fluid communication with the wellbore string or an annulus of the wellbore. The thermal spray assembly is coupled to the housing and sprays a damaged section of the casing with a thermal spray to repair the damaged section. The housing flows an inert gas received from the wellbore string or the annulus of the wellbore and through the fluid channel into the repair zone until an oxygen in the repair zone is substantially removed from the repair zone.

A repairing assembly includes a housing, a packer, and a thermal spray assembly. The housing is attached to a wellbore string disposed within a wellbore with casing. The packer is coupled to the housing. The packer is set on a wall of the wellbore to bound a repair zone defined between the packer and an end of the housing opposite the packer. The housing or the packer includes a fluid channel in fluid communication with the wellbore string or an annulus of the wellbore. The thermal spray assembly is coupled to the housing and sprays a damaged section of the casing with a thermal spray to repair the damaged section. The housing flows an inert gas received from the wellbore string or the annulus of the wellbore and through the fluid channel into the repair zone until an oxygen in the repair zone is substantially removed from the repair zone.

System and methods for cleaning debris or particulates from a wellbore using foam is provided, including predicting if a foam cleanout of a well is feasible by calculating foam properties at each of a number of segments in a well during a foam cleanout, comparing the foam properties to screening limits, providing an output to indicate if a foam cleanout is feasible. If feasible, the foam cleanout is performed.

Friction-reducing compositions useful for reducing Operating Torque in a drilling operation are described. Methods of conducting drilling operations using such friction-reducing compositions and lubricant compositions formed from blends of the friction-reducing composition with an oil-based mud composition are also described.