A system and method for determining fluid inflow into a wellbore. The system may include a drill string including an earth-boring tool. The drill string may further include a first array of sensors arranged radially about the drill string in a region of the drill string after the earth-boring tool. The drill string may be configured to be inserted into the wellbore and the first array of sensors may be configured to detect an inflow of fluid into the wellbore through a change in an environmental property of the wellbore.

An example laser tool is configured to operate within a wellbore of a hydrocarbon-bearing rock formation. The laser tool includes one or more optical transmission media as part of an optical path originating at a laser generator configured to generate a laser beam having an axis. The laser tool includes an optical element for receiving the laser beam from the one or more optical transmission media and for output to the hydrocarbon-bearing rock formation. The laser tool includes a purging head for removing dust or vapor from a path of the laser beam. The purging head is for discharging two or more purging gas streams. The purging head may include a coaxial flow assembly and a helical flow assembly. A coaxial purging gas stream may flow in a direction parallel to the axis. A helical purging gas stream may flow in a helical pattern around and substantially along the axis.

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.

Overbalanced drilling (OBD) is known to be cheap and simple but formation damage and reduced rate of penetration (ROP) are some of its disadvantages. However, underbalanced drilling (UBD) minimizes formation damage and achieve high ROP, but it is expensive, complex and can't be applied in many cases.

This application introduces a new technique that incorporates the advantages and avoids the disadvantages of these drilling systems and is referred to as Dynamic Underbalanced Drilling (DUBD).

In DUBD a pressure drop at the environ of the bit, below and around, is created that is restored to normal pressure above the bit and such conditions requires some minor modifications to the design of drill bit. Thus at the zone located below and around the bit underbalance conditions are dominated while the rest of the hole is overbalanced.

The anticipated cost of this technique is nearly zero and it is expected to save much of drilling costs. DUBD is expected to provide higher ROP that may exceed ordinary UBD in some cases, so saves time, reduce formation damage, saves costs (cheaper than OBD) and enables gathering information about the reservoir while drilling. This can save some of logging and testing costs. In addition, DUBD may reduce drilling problems, particularly time sensitive problems, and overcome problems of UBD. Furthermore, it can be used safely in over pressurized shale and salt formations, where UBD is not recommended.

An underbalanced drilling system is provided. A bottomhole assembly includes a drill bit drilling a wellbore in a formation underbalanced. The bottomhole assembly includes a telemetry sub. A telemetry component transmits signals in real-time between the telemetry sub of the bottomhole assembly and a controller on the surface. A drill string is coupled with the bottomhole assembly, and the drill string includes a plurality of drill collars. The drill collars form a channel through which drilling fluid flows from the surface to the bottomhole assembly. The drill string is inserted into the wellbore by a hydraulic work over unit. A continuous circulation component provides continuous circulation of the drilling fluid while a new drill collar is coupled to the drill string. The continuous circulation component substantially maintains a wellbore density at a predetermined density.

A seal and bearing includes a seal and bearing housing, a rotatable mandrel disposed within an inner aperture of the seal and bearing housing, an upper seal carrier attached to a top side of the seal and bearing housing having a dynamic sealing element that contacts the rotatable mandrel, a plurality of tapered-thrust bearings to facilitate rotation of the rotatable mandrel including top tapered-thrust bearings indirectly mounted at a positive offset angle from a perpendicular line to a longitudinal axis of the rotating control device and bottom tapered-thrust bearings indirectly mounted at a negative offset angle from the perpendicular line to the longitudinal axis of the rotating control device, a preload spacer disposed between the top and bottom tapered-thrust bearings, and a lower seal carrier attached to a bottom side of the seal and bearing housing having a plurality of removable seal carrier trays.

A closed-loop hydraulic drilling system generates choke characteristic curves or data that more accurately reflects the relationship between the commanded choke valve position and the resulting pressure drop across the choke valve for a given flow rate and fluid density. The choke characteristic curves may be generated through a calibration procedure and then used during normal operations to more accurately monitor return flow and manage wellbore pressure. The specific gravity of an injected calibration fluid and pressure drop across the choke valve may be determined and correlated to the current choke valve position to reflect the choke characteristic curve in situ, thereby providing for more precise control of wellbore pressure and enabling condition monitoring of the choke valve. In addition, an improved closed-loop hydraulic drilling system does not require a flow meter, enabling the adoption of MPD systems in low-specification and economically constrained applications.

A stochastic control method includes determining a property of a solid present in a drilling fluid circulating within a mud circulation system and identifying a mud circulation model that dictates operation of the mud circulation system. The mud circulation model is based on one or more models of one or more uncertainties encountered during a wellbore drilling operation. The method further includes determining an accuracy of the mud circulation model based on a difference between the determined property of the solid present in the drilling fluid and a solid property of the drilling fluid as provided by the mud circulation model, and programming a controller of the mud circulation system based on the mud circulation model to modify operation of the mud circulation system.

An underbalanced drilling system is provided. A bottomhole assembly includes a drill bit drilling a wellbore in a formation underbalanced. The bottomhole assembly includes a telemetry sub. A telemetry component transmits signals in real-time between the telemetry sub of the bottomhole assembly and a controller on the surface. A drill string is coupled with the bottomhole assembly, and the drill string includes a plurality of drill collars. The drill collars form a channel through which drilling fluid flows from the surface to the bottomhole assembly. The drill string is inserted into the wellbore by a hydraulic work over unit. A continuous circulation component provides continuous circulation of the drilling fluid while a new drill collar is coupled to the drill string. The continuous circulation component substantially maintains a wellbore density at a predetermined density.

Systems and methods include a method for providing an integrated advanced visualization tool for geosteering underbalanced coiled tubing drilling (UBCTD) operations. Drilling operation data is received from different sources in real time during a drilling operation. The drilling operation data includes geological formation information recorded during the drilling operation, micropalaeontological test results of the drilling operation, drilling parameters being used during the drilling operation, cumulative productivity index calculations, and reservoir pressure information of reservoirs encountered during the drilling operation. The drilling operation data is analyzed to correlate elements of the drilling operation data by time and cumulative depth. A graph is generated in real time that includes multiple plots correlated as a function of cumulative depth over time.