Abstract: A system and method for optimized control of an assembly for drilling a borehole comprises a self-tuning, multivariable controller and an optimization engine that manipulates the setpoints of the controller such that drilling performance may be continuously optimized. The method includes evaluation of a characteristic system time constant, using this constant to compute bit ROP, using computed ROP to compute process gains, which are used to tune the multivariable controller, automatically refining controller setpoints based on controller performance, and using an optimization engine to systematically adjust controller setpoints such that drilling parameters are optimized based on any of several performance indicators, or a weighted combination of performance indicators.

Abstract: A method for creating a second borehole in an earth formation at a selected orientation relative to a first borehole, wherein a position parameter represents a position of the first borehole. The method comprises: a) providing a borehole element that generates a magnetic field; b) measuring the magnetic field; c) installing the borehole element in the first borehole; d) measuring the magnetic field in the second borehole; e) providing a finite element model of the magnetic field; f) calculating the magnetic field in the second borehole using the finite element model, and determining a difference between the calculated magnetic field in the second borehole and the measured magnetic field in the second borehole; g) adjusting the position parameter so as to minimise said difference; and h) determining a selected direction dependent on the adjusted position parameter and further drilling the second borehole in the selected direction.

Abstract: A method of controlling the direction of drilling comprising: providing a drill bit comprising mechanical cutting means forming a bit face and a plurality of nozzles for ejecting drilling fluid arranged at different azimuthal positions with respect to the bit face, and an intermediate space between an inlet port of the drill bit and the plurality of nozzles; rotating the drill bit while passing drilling fluid comprising solids through the intermediate space and the plurality of nozzles, so as to deepen the borehole; and modifying solids concentration of drilling fluid portions flowing through the plurality of nozzles while rotating the drill bit, so that the solids concentration, for the drilling fluid portion flowing through each of the nozzles, is relatively increased when the respective nozzle is in a selected first angular sector of the borehole bottom, as compared to a second angular sector.

Abstract: A distance holder for connection to, and rotation with, a drill string in an earth formation drilling device arranged to supply a jet of abrasive fluid for the purpose of providing a borehole by removing earth formation material through abrasion, comprises a chamber that is essentially rotational symmetric and which faces the earth formation material, and a jet nozzle arranged for discharging a jet of the abrasive fluid in the chamber. The chamber comprises a deflector positioned in the path of the fluid jet discharged from the jet nozzle.

Abstract: A method of drilling into an object comprises providing a drill string in a borehole in the object, the borehole having at its bottom a borehole axis, the drill string comprising a borehole-centralized jet drill head at its lower end, the jet drill head having a drill axis, and comprising a jet nozzle; providing a stabilizer means for the drill string, the stabilizer means determining an inclination angle between the borehole axis and the drill axis; and generating a fluid jet at the jet nozzle, so as to deepen the borehole, wherein the drill string is rotated while deepening the borehole. Another system comprises a drill string with an jet drill head at its lower end, the drill head being provided with a jet nozzle, a stabilizer positioned above the jet drill head, the stabilizer contacting the borehole wall, and means for rotating the drill string.

Abstract: Method of drilling a borehole into an object, the method comprising providing a first borehole section (5) extending into the object from its surface; running a first drill string part (3a) including a fluid jet drill head (10) in the first borehole section, wherein the first drill string part comprises a length of flexible tubing; generating fluid jet so as to blast with an erosive power on an impingement area of the borehole, thereby deepening the borehole to provide a second borehole section (5a), and assembling a plurality of jointed pipe elements (11) forming a second drill string part (11a) to the top of the length of flexible tubing in the course of providing the second borehole section; and hybrid drill string (16), comprising a length of flexible (3) tubing as well as a plurality of jointed pipe elements (11), and further comprising a bottomhole assembly comprising a fluid jet drill head (10).

Abstract: A method of drilling comprises providing a drill string in a borehole, the drill siring comprising an abrasive jet drill head including a jet nozzle, and providing a fluid passageway between the object's surface and the jet nozzle; supplying a fluid mixture comprising magnetic particles to the abrasive jet drill head and blasting from the nozzle an abrasive jet into impingement with the object; and modulating a jetting concentration of magnetic particles in the abrasive jet by modulating a magnetic field a first value, at which magnetic particles are collected from the fluid mixture, and a second value, at which magnetic particles are released into the fluid mixture. Further, an abrasive jet drilling assembly comprising a modulation means for modulating the concentration of the magnetic abrasive particles in the fluid jet a modulation control means for selectively changing a magnetic field between first and second values.

Abstract: A method of drilling comprises providing a drill string in a borehole, the drill string comprising an abrasive jet drill head including a jet nozzle and providing a passageway for fluid to the nozzle; supplying a supply fluid comprising a supply concentration of abrasive particles to the jet drill head; generating an jet comprising a jetting concentration of abrasive particles at the nozzle, wherein the jetting concentration depends on the supply concentration; and modulating the jetting concentration; wherein the supply concentration is modulated in order to modulate the jetting concentration. Further, an drilling assembly comprising an drill head with a jet nozzle, a passageway for fluid from a drill string to the jet nozzle, and a modulation means arranged along the fluid passageway for modulating the concentration of abrasive particles in fluid flowing through the fluid passageway towards the jet nozzle.

Abstract: Method for determining a property of a formation material in the course of a jet drilling operation, wherein a fluid jet is blasted with erosive power into impingement with the formation material, the method comprising postulating a relationship between the erosive power and a removal rate of formation material as a result of the impingement of the fluid jet with the erosive power on said formation material, the relationship comprising a parameter related to at least one property of the formation material; determining removal rates of formation material for at least two settings of erosive power; and determining the at least one property of the formation material from the relationship and the determined removal rates in dependence on erosive power.

Abstract: A distance holder for connection to, and rotation with, a drill string in an earth formation drilling device arranged to supply a jet of abrasive fluid for the purpose of providing a borehole by removing earth formation material through abrasion, comprises a housing with a chamber which is essentially rotational symmetric and which is to face the earth formation material, and a jet nozzle which arranged for discharging a jet of the abrasive fluid in the chamber, the housing comprising at least one slot for allowing the abrasive fluid to leave the chamber. The slot is continued over the housing outer surface so as to counteract rolling motions of the particles which are comprised in the abrasive fluid.

Abstract: A method for supplying a jet of abrasive fluid for the purpose of providing a borehole by removing earth formation material through abrasion comprises a drill string and a drilling assembly connected to the drill string. The drilling assembly comprises a jetting device with a mixing space, a drilling fluid, a particle inlet, an abrasive fluid outlet for discharging a mixture of drilling fluid and magnetic particles, and a magnetic particle circulation system comprising a supporting surface which is exposed to a return stream along the drilling assembly. The method includes fixing a magnetic device with respect to the supporting surface, selecting a magnetic field density that which increases along the sloping supporting surface, attracting magnetic particles onto the supporting surface, and making the magnetic particles move over the sloping supporting surface (under the influence of the magnetic field of the magnetic device.

Abstract: A device is provided for feeding a plurality of particles into a stream at a controlled rate, the device comprising a conduit having a flow passage for feeding the particles into the stream, and pulsating means for inducing a pulsed flow of the particles through the flow passage.

Abstract: A system is disclosed for drilling a wellbore (1) into an earth formation. The system comprises an expandable tubular element (4) extending into the wellbore, whereby a lower end portion (11) of the wall of the tubular element (8) extends radially outward and in axially reverse direction so as to define an expanded tubular section (10) extending around a remaining tubular section (4) of the tubular element. The expanded tubular section is extendable by downward movement of the remaining tubular section relative to the expanded tubular section whereby said lower end portion (14) of the wall bends radially outward and in axially reverse direction.

Abstract: A device is provided for feeding a plurality of particles into a stream at a controlled rate, the device comprising a conduit having a flow passage for feeding the particles into the stream, and pulsating means for inducing a pulsed flow of the particles through the flow passage.

Abstract: A distance holder for connection to, and rotation with, a drill string in an earth formation drilling device arranged to supply a jet of abrasive fluid for the purpose of providing a borehole by removing earth formation material through abrasion, comprises a housing with a chamber which is essentially rotational symmetric and which is to face the earth formation material, and a jet nozzle which arranged for discharging a jet of the abrasive fluid in the chamber, the housing comprising at least one slot for allowing the abrasive fluid to leave the chamber. The slot is continued over the housing outer surface so as to counteract rolling motions of the particles which are comprised in the abrasive fluid.

Abstract: A distance holder for connection to, and rotation with, a drill string in an earth formation drilling device arranged to supply a jet of abrasive fluid for the purpose of providing a borehole by removing earth formation material through abrasion, comprises a chamber that is essentially rotational symmetric and which faces the earth formation material, and a jet nozzle arranged for discharging a jet of the abrasive fluid in the chamber. The chamber comprises a deflector positioned in the path of the fluid jet discharged from the jet nozzle.

Abstract: A method for supplying a jet of abrasive fluid for the purpose of providing a borehole by removing earth formation material through abrasion comprises a drill string and a drilling assembly connected to the drill string. The drilling assembly comprises a jetting device with a mixing space, a drilling fluid, a particle inlet, an abrasive fluid outlet for discharging a mixture of drilling fluid and magnetic particles, and a magnetic particle circulation system comprising a supporting surface which is exposed to a return stream along the drilling assembly. The method includes fixing a magnetic device with respect to the supporting surface, selecting a magnetic field density that which increases along the sloping supporting surface, attracting magnetic particles onto the supporting surface, and making the magnetic particles move over the sloping supporting surface (under the influence of the magnetic field of the magnetic device.

Abstract: A system and method for making a hole in an object, the system having jet means for generating an abrasive jet formed of a mixture of a fluid and abrasive particles, and for blasting the abrasive jet with an erosive power into impingement with the object in an impingement area, thereby eroding the object in the impingement area. The system further has a rotating means for moving the impingement area along a selected circular trajectory in the hole about its circumference, and modulation means for modulating the erosive power of the abrasive jet while the impingement area is being moved along the selected trajectory.

Abstract: A tool for excavating an object comprises a jetting system having a nozzle arranged to receive a fluid and abrasive particles via an abrasive particle inlet, and arranged to impinge the object to be excavated with a jetted stream of the fluid mixed with the abrasive particles, the tool further having a recirculation system arranged to recirculate at least some of the abrasive particles from a return stream, downstream of the impingement of the jetted stream with the object to be excavated, back to the jetting system via the abrasive particle inlet, the abrasive particle inlet having an entrance window in which a device in a path fluidly connecting the return stream with the entrance window keeps the abrasive particle inlet free from objects of the same size or larger than the size of the window while allowing passage of the abrasive particles.

Abstract: A nozzle unit for generating an abrasive jet. The nozzle unit has a first nozzle connected to a pressurized carrier fluid supply; a mixing chamber in which the first nozzle discharges; and a second nozzle connected to the mixing chamber. An abrasive particle inlet discharges in the mixing chamber. A proportion of the cross sectional area of the first nozzle opening (A1) and the cross sectional area of the second nozzle opening (A2) is in a range of 0.50-1.0.