Abstract: A closed-loop circulating system for drilling wells has control of the flow rates in and out of the wellbore. Kicks and fluid losses are quickly controlled by adjusting the backpressure. Kick tolerance and tripping margins are eliminated by real-time determination of pore and fracture pressure. The system can incorporate a rotating BOP and can be used with underbalanced drilling.

Abstract: Assembly for pressure control when drilling underground to locate or produce hydrocarbons; whereby the drilling is done by means of a drill string with fluid circulation down through the drill string and up through an annulus between the drill string and the open hole or casing, as the underground in the open hole may comprise one or both of: areas with formation strength which is unable to withstand the pressure from the fluid circulation without fracturing and areas with formation pressure which cannot be combined with each other or the fluid circulation pressure without the fluid unintentionally leaking in or out from the above-mentioned areas.

Abstract: A purely mechanical hydraulic control system includes at least one drilling fluid chamber and a hydraulic fluid chamber. A system pressure spring is deployed in one of the drilling fluid chamber(s) between a positioning piston and a system pressure piston. The spring is disposed to pressurize oil in the hydraulic fluid chamber via applying a spring force to the system pressure piston. When the system is actuated (e.g., via turning on the mud pumps), the positioning piston is urged in place against a stop (e.g., a shoulder) thereby compressing the system pressure spring and pressurizing oil in the hydraulic chamber. The invention advantageously converts highly variable drilling fluid pressure to a near constant pressure hydraulic fluid.

Abstract: A system for forming a subterranean wellbore may include a pump and an additive supply. The pump pumps a drilling fluid into the wellbore while also generating a pressure differential that draws an additive across a supply line connected to the additive supply. The drilling fluid may be a gas or a liquid. A method for forming a wellbore may include drilling the wellbore, circulating a drilling fluid in the wellbore using a pump; and supplying an additive to the drilling fluid by flowing the additive across a supply line using a pressure differential generated by the pump. The pump may generate a vacuum pressure at a supply line outlet and/or create a pressure differential in the supply line. The flow of additive across the supply line may be regulated and/or stopped when the pump is not operating.

Abstract: A method for controlling formation pressure during drilling includes pumping a drilling fluid through a drill string in a borehole, out a drill bit at the end of the drill string into an annular space. The drilling fluid is discharged from the annular space proximate the Earth's surface. At least one of a flow rate of the drilling fluid into the borehole and a fluid flow rate out of the annular space is measured. Pressure of the fluid in the annular space proximate the Earth's surface and pressure of the fluid proximate the bottom of the borehole are measured. Pressure of the fluid proximate the bottom of the borehole is estimated using the measured flow rate, annular space pressure and density of the drilling fluid. A warning signal is generated if difference between the estimated pressure and measured pressure exceeds a selected threshold.

Abstract: A method of controlling operation of a rock drilling rig, and a rock drilling rig. A rate of flow of a flushing medium of the rock drilling rig is determined, and the operation of the rock drilling rig is controlled on the basis of the determined rate of flow by influencing pressure of the flushing medium.

Abstract: A method and apparatus for predicting and controlling secondary kicks, while dealing with a primary kick experienced when drilling an oil and gas well. The method includes a step of determining whether a different pressure per cubic meter of mud pit volume has been caused by a secondary kick by subtracting shut in drill pipe pressure (SIDPP) from shut in casing pressure (SICP) and dividing the derived sum by a kick volume in KPa per cubic meter from the primary kick. A further step is then taken of increasing casing pressure until casing pressure equals pit gain times (X) rate of change in casing pressure per cubic meter of pit gain plus (+) SIDPP.

Abstract: Exhaust pressure from at least one actuator (34,36) which can tilt joint 6 of a bottom hole assembly 4 can be utilized to determine the direction 26 tiltable joint 6 is pointing (e.g., orientation, angular displacement, and/or inclination and azimuth). In one embodiment, a known exhaust pressure can be correlated to a known orientation and/or angular displacement, and the measured exhaust pressure can be compared to the known exhaust pressure to determine the orientation and/or angular displacement. In another embodiment, the flow rate of fluid exhausted from an actuator (34,36) can be derived from the exhaust pressure. The exhaust flow rate can then be used to calculate the state of actuation, which can allow determination of the angular displacement of the tiltable joint 6. Orientation and/or angular displacement with respect to the bottom hole assembly 4 can be resolved into an inclination and azimuth with respect to a formation 14.

Abstract: Aspects of this invention include a downhole tool (such as a steering tool) including first and second sensor sets for measuring substantially instantaneous drill string rotation rates. Each of the sensor sets includes at least one accelerometer disposed to measure cross-axial acceleration components. Embodiments of this invention advantageously enable gravitational and tool shock/vibration acceleration components to be cancelled out, thereby improving accuracy. Moreover, exemplary embodiments of this enable stick/slip conditions to be detected and accommodated.

Abstract: A method of dynamically controlling open hole pressure within a wellbore having a drill string positioned therein. The method comprising the steps of pumping a fluid down the drill string, into an annulus formed by the drill string and the interior of the wellbore, and then subsequently up the annulus to the surface of the ground; selectively applying wellhead pressure to the annulus through selectively pumping an additional quantity of the fluid or a quantity of a secondary fluid across the annulus; and, controlling the application of wellhead pressure applied to the annulus by controlling one, or both, of (a) the operation of a wellhead pressure control choke, and (b) the flow rate of the additional quantity of fluid or the secondary fluid pumped across the annulus, to thereby maintain open hole pressure within a desired range.

Abstract: Drilling system and method for drilling a bore hole into an earth formation, the bore hole having an inside wall. A drill string reaches into the bore hole and leaves a drilling fluid return passage between the drill string and the bore hole inside wall. A drilling fluid discharge conduit is in fluid communication with the drilling fluid return passage, and pump means are provided for pumping a drilling fluid through the drill string into the bore hole and to the drilling fluid discharge conduit via the drilling fluid return passage. The drilling fluid back pressure is controlled utilizing back pressure control means for controlling back pressure means. The system further provides fluid injection means comprising an injection fluid supply passage fluidly connecting an injection fluid supply with the drilling fluid return passage and further comprising an injection fluid pressure sensor arranged to provide a pressure signal in accordance with an injection fluid pressure in the injection fluid supply passage.

Abstract: In one aspect of the invention a drill bit comprises an axis of rotation a body and a working face. The body comprises a fluid passageway with a first seat and houses a jack element substantially coaxial with the axis. A stop element is disposed within the passageway and has a first near-sealing surface. The jack element has a shaft intermediate an indenting end and a valve portion. The valve portion has a second near-sealing surface disposed adjacent the first near-sealing surface and a second seat disposed adjacent the first seat. As a formation strongly resists the jack element, the distance between the sealing surfaces narrows. This causes an increase in fluid pressure within the passageway and forces the indenting end down into the formation. This movement of the jack element relieves the pressure build up such that the formation pushes the jack element back, thereby oscillating the jack element.

Abstract: In one aspect of the invention, a downhole tool string component comprises a fluid passageway formed between a first and second end. A valve mechanism is disposed within the fluid passageway adapted to substantially cyclically build-up and release pressure within the fluid passageway such that a pressure build-up results in radial expansion of at least a portion of the fluid passageway and wherein a pressure release results in a contraction of the portion of the fluid passageway. The valve mechanism disposed within the fluid passageway comprises a spring. Expansion and contraction of the portion of the fluid passageway varies a weight loaded to a drill bit disposed at a drilling end of the drill string.

Abstract: A closed-loop circulating system for drilling wells has control of the flow rates in and out of the wellbore. Kicks and fluid losses are quickly controlled by adjusting the backpressure. Kick tolerance and tripping margins are eliminated by real-time determination of pore and fracture pressure. The system can incorporate a rotating BOP and can be used with underbalanced drilling.

Abstract: Techniques for detecting a kick in a borehole include acquiring a set of measurements with a sonic tool in the borehole; determining borehole mud slowness from the set of measurements; and comparing the mud slowness with a selected criterion, wherein the determining the mud slowness includes determining fluid mode slowness as a function of frequency for at least one fluid mode, and determining the mud slowness from the fluid mode slowness.

Abstract: An oscillating valve driven by the pressure in a mud pulser develops a pressure variation in the mud pulse signal that is at a frequency that is different than the frequencies of the mud system. The oscillating valve is coupled to or integral with the pulse drive cylinder, whether the drive means for operation of the pulser is upstream or downstream from the orifice. A bistable valve improves performance of the transmitting element at low flow rates by providing a toggle mechanism which assures positive seating of the bistable valve.

Abstract: A method for controlling formation pressure during the drilling of a borehole through a subterranean formation includes selectively pumping a drilling fluid through a drill string extended into a borehole, out a drill bit at the bottom end of the drill string, and into an annular space between drill string and the borehole. The drilling fluid is discharged to a reservoir to clean the drilling fluid for reuse. Annular space fluid pressure is selectively increased to maintain a selected fluid pressure proximate the bottom of the borehole by applying fluid pressure to the annular space. The selective increasing includes controlling an aperture of an orifice operatively coupled between the annular space and the reservoir. Fluid from the annular space is discharged other than through the orifice when the annular space fluid pressure exceeds a selected value, or drops below a selected value.

Abstract: A closed-loop circulating system for drilling wells has control of the flow rates in and out of the wellbore. Kicks and fluid losses are quickly controlled by adjusting the backpressure. Kick tolerance and tripping margins are eliminated by real-time determination of pore and fracture pressure. The system can incorporate a rotating BOP and can be used with underbalanced drilling.

Abstract: A method for controlling formation pressure during the drilling of a borehole through a subterranean formation includes selectively pumping a drilling fluid through a drill string extended into a borehole, out a drill bit at the bottom end of the drill string, and into an annular space between drill string and the borehole. The drilling fluid is discharged from the borehole to a reservoir to clean the drilling fluid for reuse. An annular space fluid pressure is selectively increased to maintain a selected fluid pressure proximate the bottom of the borehole by applying fluid pressure to the annular space. The selective increasing includes controlling an aperture of an orifice operatively coupled between the annular space and the reservoir. A formation fluid pressure is predicted at a depth below a lowermost depth to which the borehole is drilled and the aperture is adjusted to maintain a selected pressure in the borehole in response to the predicted formation fluid pressure.

Abstract: An arrangement and a method to control and regulate the bottom hole pressure in a well during subsea drilling at deep waters: The method involves adjustment of a liquid/gas interface level in a drilling riser up or down. The arrangement comprises a high pressure drilling riser and a surface BOP at the upper end of the drilling riser. The surface BOP havs a gas bleeding outlet. The riser also comprises a BOP, with a by-pass line. The drilling riser has an outlet at a depth below the water surface, and the outlet is connected to a pumping system with a flow return conduit running back to a drilling vessel/platform.

Abstract: A method for communicating with a downhole tool located in a subterranean borehole is disclosed. Exemplary embodiments of the method include encoding data and/or commands in a sequence of varying drill string rotation rates and drilling fluid flow rates. The varying rotation rates and flow rates are measured downhole and processed to decode the data and/or the commands. In one exemplary embodiment, commands in the form of relative changes to current steering tool offset and tool face settings are encoded and transmitted downhole. Such commands may then be executed, for example, to change the steering tool settings and thus the direction of drilling. Exemplary embodiments of this invention advantageously provide for quick and accurate communication with a downhole tool.

Abstract: The preferred pulser is a mud powered oscillator powered by the pressure variation produced across the signal valve by the unstable action. The signal valve comprises a poppet and cooperating orifice. The pressure drop across the orifice is used to urge the poppet away from the orifice and an opposing spring drives it toward the orifice. The preferred poppet control is a permanent magnet that secures the poppet in at least the signal valve open position. To generate a pulse, the permanent magnet is opposed by a magnetizing coil arranged and powered by the associated MWD instrument to oppose the permanent magnet, to release the poppet to close the signal valve. The pulser is arranged to provide a generally central axially extending bore to accept a conductor extending axially through the pulser. Optional features include an acceleration compensator, and a mud powered electric energy generator. Optional features include hydraulic actuation and control of the poppet.

Abstract: A method for drilling a borehole includes; providing a drill string of drill pipe including a center bore, a distal end, a bit assembly at the distal end; hanging a liner from the drill string, thereby forming an annular space between the drill string and the liner and with the bit assembly extending from a lower end of the liner; positioning the drill string with the liner attached thereto in a borehole such that a second annular space is formed between the liner and the borehole wall; operating the bit assembly to proceed with drilling the borehole; and circulating drilling fluid down through the center bore of the drill string out through the bit assembly and down through the second annular space between the liner and the borehole wall, the drilling fluid returning up through the annular space between the drill string and the liner.

Abstract: A valve assembly connects into a drill string for opening and closing at least one inner passage within the drill string of the drill string. The valve assembly includes an annular valve assembly carried in an annular passage that moves between the open and closed positions in response to downward fluid pressure from the surface through the annular passage. The valve assembly also includes an inner valve assembly carried in an inner passage of the drill string. The inner valve assembly is a two-way valve that is actuated between open and closed positions by pressure pulses from the surface through the inner passage. The valve assembly can be used within coiled tubing.

Abstract: A closed-loop circulating system for drilling wells has control of the flow rates in and out of the wellbore. Kicks and fluid losses are quickly controlled by adjusting the backpressure. Kick tolerance and tripping margins are eliminated by real-time determination of pore and fracture pressure. The system can incorporate a rotating BOP and can be used with underbalanced drilling.

Abstract: A downhole valve device (1) in a drill string (14) in a petroleum well (2) and method for maintaining optimal annular fluid velocity and wellbore pressure. The device comprises a valve housing (20) connected between adjacent segments (12, 13) of the drill string. The valve housing is further provided with at least one valve (23) arranged to open and close to the flow of drilling fluid based on measured values of downhole physical parameters or on signals from the surface in order to permit the through-flow of a sufficient volume of drilling fluid necessary to adjust and maintain the annular fluid velocity of the drilling fluid and the wellbore pressure within optimal operating conditions.

Abstract: A drilling system includes a pressure sensor disposed on a drill string in the wellbore, the sensor responsive to pressure of a drilling fluid disposed in an annular space between a wall of the wellbore and the drill string, and a processor operatively coupled to the pressure sensor. The processor is adapted to operate a drill string release controller to release the drill string into the wellbore so as to maintain an equivalent density of the drilling fluid substantially at a selected value. A method for automatically drilling a wellbore includes measuring pressure of a drilling fluid in an annular space between a wall of the wellbore and a drill string in the wellbore, and automatically controlling a rate of release of the drill string in response to the measured pressure so as to maintain an equivalent density of the drilling fluid substantially at a selected value.

Abstract: A method for drilling a wellbore in a formation using a drilling fluid, wherein the drilling fluid has a first temperature, and wherein the wellbore has a first wellbore depth. In one embodiment, the method comprises determining at least one fracture gradient, wherein the fracture gradient is determined at about the first wellbore depth; increasing the temperature of the drilling fluid from the first temperature to a desired temperature at about the first wellbore depth; drilling into the formation at increasing wellbore depths below the first wellbore depth, wherein at least one equivalent circulating density of the drilling fluid is determined at about the first wellbore depth; and setting a casing string at a depth at which the equivalent circulating density is about equal to or within a desired range of the fracture gradient. In other embodiments, an automated system is used to maintain the temperature of the drilling fluid at about first wellbore depth.

Abstract: A method and a computer program for controlling a drilling cycle in a rock drilling apparatus, and a rock drilling apparatus. In accordance with the invention, each drilling unit in the rock drilling apparatus is monitored during a drilling period, and a drilling sequence of a control unit in the rock drilling apparatus is updated at predetermined intervals during the drilling period. The total time of the drilling and the time elapsed for different operations can be registered. In addition, according to an embodiment, the drilling sequence is changed during updating, if changes occur in the drilling conditions during the drilling period.

Abstract: A hybrid choke control system wherein the traditional choke experience is manifest in auditory and visual feedback mechanisms which are emulated by a digital control system enabling direct control of either position or back pressure associated with an adjustable choke device. The present invention enhances safety and efficiency when used in association with oil field drilling operations and in particular when applied to a device which provides the user with enhanced control capabilities for direction controlling the back pressure and position associated with drilling chokes during down hole operations.

Abstract: A method and system for averting or mitigating undesirable drilling events during a drilling process is disclosed. The state of the drilling rig is detected, preferably automatically, based on surface and/or downhole measurement data. One or more undesirable drilling events are detected by correlating the acquired measurement data with the detected state. A drilling rig action is determined which averts or mitigates a detected undesirable drilling event. Finally, the drilling process is overridden by commanding performance of the action. The algorithm used in detecting the most likely rig state is preferably probabilistic in nature, and is even more preferably based on particle filtering techniques.

Abstract: The present invention provides drilling systems for drilling subsea wellbores. The drilling system includes a tubing that passes through a sea bottom wellhead and carries a drill bit. A drilling fluid system continuously supplies drilling fluid into the tubing, which discharges at the drill bit bottom and returns to the wellhead through an annulus between the tubing and the wellbore carrying the drill cuttings. A fluid return line extending from the wellhead equipment to the drilling vessel transports the returning fluid to the surface. In a riserless arrangement, the return fluid line is separate and spaced apart from the tubing. In a system using a riser, the return fluid line may be the riser or a separate line carried by the riser. The tubing may be coiled tubing with a drilling motor in the bottom hole assembly driving the drill bit.

Abstract: An apparatus and method for removing cuttings in a deviated borehole using drilling fluids. The apparatus includes a pipe string and a bottom hole assembly having a down hole motor and bit for drilling the borehole. The pipe string has one end attached to the bottom hole assembly and does not rotate during drilling. The apparatus and methods raise at least a portion of the pipe string in the deviated borehole to remove cuttings from underneath the pipe string portion.

Abstract: An automated method and system for recognizing a well control event includes determining a state of drilling operations. When drilling operations are in a circulating state, a benchmark for a relative flow value. The relative flow value is based on a flow of drilling fluid into a well bore and a flow of drilling fluid out of the well bore. A limit on variation of the relative flow value is determined from the benchmark. A cumulative sum for the relative flow value is determined over time in response to the relative flow value exceeding the limit. A well control event is recognized based on the cumulative sum.

Abstract: A method for simulating a drilling tool assembly having a drill string and a drill bit. The method includes simulating a dynamic response of the drill string; simulating a dynamic response of the drill bit; and resolving the dynamic response of the drill string and the dynamic response of the drill bit into a dynamic response of the drilling tool assembly.

Abstract: A method for drilling a well below a body of water as disclosed which includes injecting into the well, at a depth below the water surface, a liquid having a lower density than a density of a drilling mud producing a mixture of drilling mud and low-density liquid in the well. The mixture of drilling mud and low-density liquid is withdrawn from an upper end of the well. The drilling mud and the low-density liquid are separated, with at least a portion of the separated low-density liquid returned to the depth below the water surface and at least a portion of the separated drilling mud returned to an upper end of the drill string.

Abstract: A hybrid choke control system wherein the traditional choke experience is manifest in auditory and visual feedback mechanisms which are emulated by a digital control system enabling direct control of either position or back pressure associated with an adjustable choke device. The present invention enhances safety and efficiency when used in association with oil field drilling operations and in particular when applied to a device which provides the user with enhanced control capabilities for direction controlling the back pressure and position associated with drilling chokes during down hole operations.

Abstract: Methods and systems are provided for varying fluid pressure in a circulation system while circulating a kick out of a well bore 30 drilled through a subterranean formation using a drilling rig 25 and a drill string 50. The kick may be automatically circulated out of the well bore and/or a kill fluid may be circulated into the well bore. A controller 100 reduces the circulation rate by automatically controlling the rate of the pump 90 and the position of well bore choke 70. Various sensors interconnected with the controller may be used to maintain circulation system operation. The controller may control various components utilized in the circulation procedure to maintain a substantially constant bottom hole pressure on the formation while circulating the kick out of the well.

Abstract: A method for optimizing drilling fluid hydraulics when drilling a well bore is disclosed. The drilling fluid is supplied by a surface pump through a drill string to a drill bit. The method has the step of adjusting the flow rate of a surface pump and a fluid pressure drop across the drill bit while drilling such that the drilling fluid hydraulics are optimized for a given drilling condition. In order for the flow through all the devices in the drill string to also be optimized, the flow through the devices is adjusted, thereby setting the pressure drop and the fluid flow rate through each device. As required for the overall system, the flow from the surface pump is increased or decreased as necessary.

Abstract: Disclosed is an apparatus for preparing variable density drilling muds. The invention is particularly useful in offshore operations where storage and transportation of consumable materials is an important economic issue. One version of the apparatus is a portable apparatus requiring minimal deck space that can be used as needed and then removed. The invention is particularly useful during offshore dynamic kill drilling.

Abstract: Methods and apparatus for drilling subsea wells in deep water using dual-gradient drilling techniques. One preferred embodiment includes a high pressure riser running from a drilling platform at the surface to the seafloor. The base of the riser is connected to a wellhead that is anchored to the seafloor. Pressure control equipment is disposed on the upper end of the riser at the drilling platform. A coiled tubing drill string is run through the riser and into the subsea formation. The drill string preferably includes a pressure sensing device that can be used in transmitting real-time downhole pressure data to the surface. A riser injection system is provided to inject a lower density fluid into the riser annulus in order to reduce the density of the fluids in the riser annulus and therefore reduce the hydrostatic pressure within the wellbore.

Abstract: An automated method and system for recognizing a well control event includes determining a state of drilling operations. When drilling operations are in a circulating state, a benchmark for a relative flow value. The relative flow value is based on a flow of drilling fluid into a well bore and a flow of drilling fluid out of the well bore. A limit on variation of the relative flow value is determined from the benchmark. A cumulative sum for the relative flow value is determined over time in response to the relative flow value exceeding the limit. A well control event is recognized based on the cumulative sum.

Abstract: A method and apparatus for controlling the riser base pressure and detecting well control problems, such as kicks or lost circulation, during drilling of an offshore well using a gas-lifted riser. The pressure control apparatus preferably includes two separate control elements, one to adjust the pressure at the surface (prs) and the mass flow rate out of the top of the riser ({dot over (m)}o) to compensate for changes in riser base pressure (prb) and the other to adjust either or both of the boost mud flow rate (qb) and lift gas flow rate (qg) to maintain a constant or nearly constant mass flow rate entering the base of the riser ({dot over (m)}i). According to the method of the present invention, the well return flow rate (qw) is preferably determined by directly measuring various other parameters and then computing qw from the measured parameters. The computed value of qw may be compared to the drill string flow rate (qc) to detect well control problems, such as kicks or lost circulation.

Abstract: A ground drilling machine comprises a controller for automatically controlling the injection of working liquid according to the output signal output as a function of the rotating condition of the pilot head 20. When the pilot head 20 is driven forward or backward, working liquid can be injected by switching the working liquid transfer valve 111 so long as the pilot head 20 is revolving in order to improve the digging efficiency, the soil delivering efficiency and the cooling efficiency of the machine. The injection of working liquid can be suspended when the direction of propelling the pilot head 20 is shifted while stopping the revolution of the pilot head 20 because no working liquid is required for delivering the dug soil and cooling the leading body. Thus, working liquid can be injected always at an optimal rate depending on the rotating condition of the pilot head 20 to suppress any waste of working liquid and reduce the construction cost.

Abstract: The present invention provides drilling systems for drilling subsea wellbores. The drilling system includes a tubing that passes through a sea bottom wellhead and carries a drill bit. A drilling fluid system continuously supplies drilling fluid into the tubing, which discharges at the drill bit bottom and returns to the wellhead through an annulus between the tubing and the wellbore carrying the drill cuttings. A fluid return line extending from the wellhead equipment to the drilling vessel transports the returning fluid to the surface. In a riserless arrangement, the return fluid line is separate and spaced apart from the tubing. In a system using a riser, the return fluid line may be the riser or a separate line carried by the riser. The tubing may be coiled tubing with a drilling motor in the bottom hole assembly driving the drill bit.

Abstract: Methods and systems are provided for varying fluid pressure in a circulation system while circulating a kick out of a well bore 30 drilled through a subterranean formation using a drilling rig 25 and a drill string 50. The kick may be automatically circulated out of the well bore and/or a kill fluid may be circulated into the well bore. A controller 100 reduces the circulation rate by automatically controlling the rate of the pump 90 and the position of well bore choke 70. Various sensors interconnected with the controller may be used to maintain circulation system operation. The controller may control various components utilized in the circulation procedure to maintain a substantially constant bottom hole pressure on the formation while circulating the kick out of the well.

Abstract: A down hole motor assembly includes a hydraulic drive portion, a drill bit operatively connected to the drive portion and a disengage mechanism (11) arranged to disengage drive to the drill bit. The disengage mechanism (11) is arranged to be actuated by supplying drilling fluid to the drive portion at a flow rate which is greater than the flow rate at which fluid is supplied to run the drive portion during normal drilling. The disengage mechanism is arranged to be re-set so that drive is reconnected to the drill bit when the fluid supply to the drive portion is shut off.

Abstract: A method of drilling a well having a first tubular member extending from the surface of the well to a position proximate the bottom of the well. The first tubular member has an inner annulus therethrough. A fluid is pumped into the well through the inner annulus of the first tubular member to flush drilling cuttings out of the well. A fluid is also injected into the well, exterior to the inner annulus, to control the bottom hole circulating pressure in the well.

Abstract: A downhole drilling method comprises producing pressure pulses in drilling fluid using measurement-while-drilling (MWD) apparatus (18) and allowing the pressure pulses to act upon a pressure responsive device (16) to create an impulse force on a portion of the drill string.

Abstract: A closed-loop circulating system for drilling wells has control of the flow rates in and out of the wellbore. Kicks and fluid losses are quickly controlled by adjusting the backpressure. Kick tolerance and tripping margins are eliminated by real-time determination of pore and fracture pressure. The system can incorporate a rotating BOP and can be used with underbalanced drilling.