A well system includes a drilling vessel, a concentric drillstring extending from the vessel into a subterranean wellbore disposed beneath a mudline, wherein the concentric drillstring is configured to circulate a drilling fluid from the drilling vessel into the wellbore along a first passage, and to circulate the drilling fluid from the wellbore to the drilling vessel along a second passage, and a subsea pump in fluid communication with the wellbore, wherein the subsea pump is configured to manage fluid pressure in the wellbore by controlling a height of a column of hydrostatic fluid disposed in the wellbore.

Lost circulation events are mitigated by determining a size and extent of a formation feature causing the loss of circulation. The formation feature may be determined based on surface drilling parameters, and can apply one or more of a mechanical specific energy, hydraulic, or aperture model. Using such model(s), the size of a fracture/void/aperture can be estimated and a treatment plan for a lost circulation vent can be determined. For instance, a mechanical specific energy of zero can indicate the presence of a void, the pressure at the standpipe can an extent of a formation feature, or the size of the formation feature can be estimated using drilling fluid flow rate, volume, pressure, or rheology. Determining a treatment plan can include selecting or designing a lost circulation material, a volume of lost circulation material, or alternative drilling methods.

This disclosure includes riser-component assemblies and methods of assembling the same that are suitable for managed pressure drilling (MPD) systems. For example, this disclosure includes integrated flow spool and isolation tool riser components that can be permanently coupled together and that can be configured to pass through a rotary table or other rig equipment.

An autonomous BOP system is provided for stopping an uncontrolled flow of formation hydrocarbons comprising two or more sensors distributed along a length of a subsea blowout preventer to monitor a drill pipe inside a blowout preventer and measure critical parameters. A computer using predictive-software monitors a blowout preventer along with material critical parameters and calculates a blowout preventer configuration and sequence to arrest a well blowout. Blowout preventer components are fine-tuned and operational modes are added to aid an arrest of a well blowout under realistic conditions.

A method of controlling lost circulation includes introducing into a wellbore a lost circulation fluid comprising: an external oil phase, an internal aqueous phase, an emulsifier, a wetting agent, a magnesia sealant, and a; retarder; contacting the lost circulation fluid with a lost circulation zone; and forming a plug adjacent the lost circulation zone by reacting the magnesia sealant with water at a wellbore temperature, thereby reducing fluid loss into the lost circulation zone.

Methods and systems for treating a subterranean formation. An example method performs a wellbore operation with a first treatment fluid, removes a flammable gaseous hydrocarbon from a well penetrating the subterranean formation; wherein the well is disposed on a wellsite, introduces the flammable gaseous hydrocarbon into a gas-to-liquid reactor located on the wellsite to produce an oleaginous liquid, produces a second treatment fluid comprising the oleaginous liquid at the wellsite, and introduces the second treatment fluid into the well.

Methods and compositions for the use of thermally responsive lost circulation materials in subterranean formations are provided. In one embodiment, the methods include introducing a treatment fluid including a base fluid and a thermally responsive lost circulation material including a thermally responsive hydrogel that includes at least one thermoresponsive polymer into a wellbore penetrating at least a portion of a subterranean formation including a loss zone; allowing the thermally responsive lost circulation material to reach a thickening transition temperature; and allowing the treatment fluid to at least partially set in the subterranean formation.

Embodiments of the disclosure provide an unfoldable device for controlling lost circulation in a target lost circulation zone in a borehole. The unfoldable device includes a sheet, a backbone, and a shell. The sheet has an unfolded state and a folded state. The backbone reinforces the sheet. The backbone includes a shape-memory material having an original state and a deformed state. The shell encapsulates the sheet in the folded state and the backbone in the deformed state. In some embodiments, the shell includes a degradable polymer that degrades in the borehole upon contact with a drilling fluid such that the sheet transitions to the unfolded state and the backbone transitions to the original state. The sheet in the unfolded state accumulates on a borehole wall at least partially covering an entrance to a macrochannel of the target lost circulation zone.

A tool for cleaning out the lower end of a cased wellbore having an installed production string. The tool is lowered down the production string until it projects from an end of the production string and into the wellbore. High pressure fluid is then sprayed from the tool’s fluid openings into nearby portions of the wellbore. Once cleaning operations are complete, the tool is carried back to the ground surface using subterranean fluid pressure.

A tool for cleaning out the lower end of a cased wellbore having an installed production string. The tool is lowered down the production string until it projects from an end of the production string and into the wellbore. High pressure fluid is then sprayed from the tool’s fluid openings into nearby portions of the wellbore. Once cleaning operations are complete, the tool is carried back to the ground surface using subterranean fluid pressure.