In accordance with one or more embodiments of the present disclosure, a drilling fluid may include a base fluid, one or more formaldehyde-based resins, and one or more water-soluble acid catalysts. The base fluid may include an aqueous or non-aqueous solution. The one or more water-soluble acid catalysts may be present in an amount sufficient to reduce the pH of the drilling fluid to less than or equal to 6. The present disclosure also describes sealed subterranean petroleum formations that include such drilling fluids and methods for sealing subterranean wellbores by utilizing such drilling fluids.

A method may comprise positioning a downhole fluid sampling tool into a wellbore, performing a pressure test operation within the wellbore, performing a pumpout operation within the wellbore, identifying when a clean fluid sample may be taken by the downhole fluid sampling tool from at least the pressure test operation and the pumpout operation, and acquiring the clean fluid sample from the wellbore. A system may comprise a downhole fluid sampling tool and an information handling machine. The downhole fluid sampling tool may further comprise one or more probes attached to the downhole fluid sampling tool, one or more stabilizers attached to the downhole fluid sampling tool, and a sensor placed in the downhole fluid sampling tool configured to measure drilling fluid filtrate.

A gel material for oil and gas conformance control operations is provided. The gel material includes a plurality of gel material components including polyacrylamide, triamine silica, and nanosilica which are added in suitable amounts to form the gel material under a gel formation condition. The present technology replaces and/or supplements conventional crosslinkers and provides enhanced polymeric gels, such as, for oil and gas field applications including wellbore strengthening, loss circulation materials, and water shut-off applications, at high temperatures. The present technology is compatible with fresh and high salinity water.

A downhole wellbore planner builds a fracture model of a wellbore using fracture data identified from geological information. Using the fracture model and a target wellbore location at the formation, the wellbore planner may identify or select one or more lost circulation materials (LCMs). The drilling operator may then procure the LCMs before drilling the wellbore. In this manner, the impact of a lost circulation event may be reduced by having the LCMs on site or nearby.

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.

Expandable tube members that are fabricated from a composite material that includes a structural plastic, which structural plastic includes phase change materials that undergo a permanent expansion upon exposure to wellbore conditions. This permanent expansion of the structural plastic causes the expandable tube member to expand radially and/or longitudinally without the use of an expansion tool. The expandable tube member can be used to control fluid loss, patch wells, stabilize a formation in a wellbore, enhance flow, provide sand screening, and repair damaged pipes, casings, or liners.

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 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 thixotropic composition having a cross-linkable polymer, cross-linking agent, initiator and a thixotropic agent. The thixotropic agent may be a clay or a saccharide polymer. The thixotropic composition may be introduced into a drill string via a batch or on-the-fly process to prevent loss of drilling fluid into the surrounding formation.