A method of reducing lost circulation includes introducing a lost circulation solution comprising Saudi Arabian volcanic ash, a curing agent, and a resin into a subsurface formation through a wellbore, wherein the Saudi Arabian volcanic ash comprises SO.sub.3, CaO, SiO.sub.2, Al.sub.2O.sub.3, Fe.sub.2O.sub.3, MgO, and K.sub.2O; and allowing the lost circulation solution to thicken within the subsurface formation, thereby forming a barrier between the subsurface formation and the wellbore to reduce lost circulation.

A drilling turbine (1) comprises a housing (2) in which a drive shaft (6) is rotatably mounted, and a turbine impeller (3) designed to set the drive shaft (6) in rotation. The drive shaft (6) is connectable to a drilling tool (4, 5). The housing has at least one drive line (9, 12) with at least one drive mouth (19), through which a drive fluid can be directed onto the turbine impeller (3). The turbine impeller (3) is connected directly to the drive shaft (6) such that, during operation, the turbine impeller (3), the drive shaft (6) and the drilling tool (4, 5) rotate at the same rotational speed. The housing (2) has a diameter of about 2.5 to about 15 cm and/or a length of about 3 cm to about 15 cm. A method for directional drilling uses a drilling turbine of this type.

A method, and related apparatus, involves providing one or more drill pipe segments and disposing a quantity of lost circulation material objects within the one or more drill pipe segments. A retention element is provided to retain the lost circulation material objects within the one or more drill pipe segments. The one or more drill pipe segments are connected to a drill string at a wellbore, and drilling fluid is flowed through the drill string. The flowing of drilling fluid through the drill string causes the retention element to release the lost circulation material objects to propagate further.

Cement slurry is prevented from coming into contact with hardening accelerator in a cementing tool in a simple manner. The method of supplying cement slurry has the steps of: adding capsule C to cement slurry, wherein capsule C is filled with hardening accelerator for the cement slurry; and supplying the cement slurry to a hole, wherein capsule C is added to the cement slurry, and the cement slurry is supplied through cementing tool 105 that is provided in the hole. Capsule C melts or collapses after a specific amount of time passes, wherein the specific amount of time is longer than a flow out time, which is a time for capsule C to flow out of cementing tool 105 after capsule C is added to the cement slurry.

Various embodiments provide methods and systems for providing sustainable and environmentally friendly fluid lighteners for use in downhole wells. The sustainable and environmentally friendly fluid lighteners may include one or more viscosifiers, one or more aphron generators, and a location-specific non-emulsifying or de-emulsifying surfactant. Various embodiments provide methods and systems for providing continuity of chemistry in downhole wells.

A body defines a central flow passage. A check valve is located within the central flow passage. The check valve is supported by the body. The check valve is arranged such that a fluid flow travels in a downhole direction during operation of the float collar. An auxiliary flow passage is substantially parallel to the central flow passage and is defined by the body. The auxiliary flow passage includes an inlet upstream of the check valve and an outlet at a downhole end of the float collar. A rupture disk seals the inlet of the auxiliary flow passage. The rupture disk is configured to burst at a specified pressure differential.

Bottom hole assemblies with a combined roller-underreamer assembly can include: a body configured to be attached to a drill pipe; an uphole ring attached to the body; a downhole ring attached to the body between the uphole ring and the downhole end of the body; a sliding ring mounted around the body between the uphole ring and the downhole ring; a set tube slidably mounted around the body between the uphole ring and the sliding ring; a reamer assembly with at least one first articulated arm with extending between the uphole ring and the downhole end of the set tube; and a roller assembly with: at least one second articulated arm extending between the uphole end of the set tube and the sliding ring; and a rolling positioned at a joint of each second articulated arm.

Provided are compositions and methods that use a true crystallization temperature reduction additive in the aqueous internal phase. An example method may comprise providing an oil-based treatment fluid in the form of an invert emulsion comprising an aqueous internal phase and an oil external phase. The aqueous internal phase may include a bromide brine and a true crystallization temperature reduction additive, wherein the bromide brine has a density of about 14.2 lbs/gal or greater. The method may further include placing the oil-based treatment fluid into a wellbore.

Provided are compositions and methods that use a true crystallization temperature reduction additive in the aqueous internal phase. An example method may comprise providing an oil-based treatment fluid in the form of an invert emulsion comprising an aqueous internal phase and an oil external phase. The aqueous internal phase may include a bromide brine and a true crystallization temperature reduction additive, wherein the bromide brine has a density of about 14.2 lbs/gal or greater. The method may further include placing the oil-based treatment fluid into a wellbore.

A torsional damping system includes a housing having an interior space. An inertia ring is located in the interior space, and a torsion fluid is located between the inertia ring and the housing. The inertia ring is rotatably installed relative to the housing. As the housing oscillates, the inertia ring damps at least a portion of the oscillation. The torsional damping system may be included in a downhole tool or bottomhole assembly, and used to damp oscillations along a drill string or along the bottomhole assembly, including between a downhole motor and a cutting tool.