A subterranean coring assembly can include a body having at least one wall that forms a cavity, wherein the cavity has a top end and a bottom end. The subterranean coring assembly can also include a first flow regulating device movably disposed within the cavity, where the first flow regulating device is configured to move from a first default position to a first position within the cavity based on first flow characteristics of fluid that flows into the top end of the cavity toward the bottom end of the cavity.

A temporary seal may be configured to be initially positioned on a seal seat within casing, and be configured to be broken or disengaged by increasing the pressure within the inner diameter of the casing past a pressure threshold. Subsequent to the temporary seal being broken, a first portion of the temporary seal may remain on the seal seat while a second portion of the temporary seal may travel downhole through a landing collar. Then, cement may be pumped within the casing, followed by a wiper plug. The wiper plug may pass the seal seat, and be locked in place on the landing collar. The cement may cure and remaining portions of the temporary seal may dissolve.

A crossover sub includes a tubular housing connected to a drill string in a wellbore, a sealing structure to seal against a wellbore wall, and a sleeve valve disposed within the housing and movable between a closed position and an open position in response to a fluid pressure in a first flow chamber or second, separate flow chamber of the housing. The first flow chamber fluidly connects an upper annulus of the wellbore to a central bore of the drill string downhole of the crossover sub. The second flow chamber fluidly connects a central bore of the drill string uphole of the sealing structure to a lower annulus of the wellbore. The sleeve valve closes the second flow chamber in response to the sleeve valve being in the closed position, and opens the second flow chamber in response to the sleeve valve being in the open position.

A method of producing petroleum from at least one open hole in at least one petroleum production zone of a hydrocarbon well comprising the steps of locating a plurality of sliding valves along at least one production tubing; inserting the plurality of sliding valves and the production tubing into the at least one open hole; cementing the plurality of sliding valves in the at least one open hole; opening at least one of the cemented sliding valves; removing at least some of the cement adjacent the opened sliding valves without using jetting tools or cutting tools to establish at least one communication path between the interior of the production tubing and the at least one petroleum production zone; directing a fracing material radially through the at least one sliding valve radially toward the at least one production zone; producing hydrocarbons from the at least one petroleum production zone through the plurality of the sliding valves the cement adjacent to which has been removed.

A downhole tool assembly for use in a drilling string includes a motor, a flow head, and a flow restrictor. The flow head is coupled to the motor and comprises a plurality of ports permitting fluid communication therethrough. The flow restrictor is in fluid communication with the flow head and comprises a plurality of ports permitting fluid communication therethrough. The flow restrictor is stationary with respect to the flow head, which rotates. As the flow head rotates, one or more of the plurality of ports of the flow head enters into and out of alignment with one or more of the plurality of ports of the flow restrictor such that fluid flow through the ports of the flow head and the flow restrictor is constrained to a cyclic, polyrhythmic pattern optionally including at least one interval where the fluid flow is substantially blocked by the flow restrictor.

A drilling motor provides rotational force within a wellbore and includes a power section within the interior of a housing, a rotor positioned within the power section, and a passage within the rotor. The passage is configured to bypass a portion of the drilling mud from above the power section within the interior of the housing to below the power section within the interior of the housing, and an interior valve at a downstream end of the passage, wherein the valve includes a rupture disc configured to close the passage when the pressure from the drilling mud is less than a threshold pressure, and to rupture to open the passage and pass the drilling mud through the valve when the pressure from the drilling mud is greater than the threshold pressure.

A drilling tool for use in a wellbore comprises a first collar having a first bore extending from a first send to a second end and an internal thread disposed on the bore at the second end. The drilling tool also comprises a second collar having a second bore extending from a third end to a fourth end and an external thread disposed on the third end. The third end is coupled to the second end of the first collar. A first set of components is housed within the first bore and a second set of components is housed on a sidewall of the second collar formed between the second bore and an outer surface of the second collar.

A method of providing an underbalance in a wellbore that includes positioning a surge assembly within the wellbore; bypassing a differential chamber that extends along a portion of the length of the surge assembly when flowing fluid through a fluid passageway that extends along the length of the surge assembly; and placing the fluid passageway in fluid communication with the air chamber to create an underbalance in the fluid passageway.

A perforating gun has shaped charges that can generate a high-pressure gas. A valve sub connects to the perforating gun and a reservoir sub connects to the valve sub. The valve sub has an enclosure with a port. A mandrel in the enclosure has a piston head and a fluid path extending at least partially through the mandrel. A sleeve is slidably mounted on the mandrel and selectively blocks fluid flow through the port. A pressure chamber in the sleeve receives the generated high-pressure gas via the fluid path. The sleeve slides toward the perforating gun after a predetermined pressure is created by the generated high-pressure gas in the pressure chamber. The reservoir sub may have at least one chamber in fluid communication with the interior of the valve sub.

A downhole drilling motor includes a motor housing having an inner bore and an outer surface. A power section includes a stator elastomer at least partially disposed within the inner bore of the motor housing. A bearing section includes an upper bearing at least partially disposed within the inner bore of the motor housing. The motor housing further includes an opening extending from the inner bore to the outer surface to provide a bypass fluid path for a fluid in the inner bore. The opening is disposed on the motor housing between a lower end of the stator elastomer and an upper end of the upper bearing. The bypass fluid path allows the downhole drilling motor to accommodate a higher flow rate of a fluid through the stator elastomer of the power section than through the upper bearing of the bearing section.