Continuous wellbore drilling system with stationary sensor measurements

Abstract

The present invention provides continuous or near continuous motion drill strings which include motion sensitive and other MWD sensors which take stationary measurements while the drilling assembly is continuing to drill the wellbore. For simultaneous continuous drilling and stationary measurements, the present invention provides a drilling assembly wherein a force application system almost-continuously applies force on the drill bit while maintaining a housing or drill collar section stationary. Motion sensitive sensors carried by the drill collar take stationary measurements. A steering device between the drill bit and the force application system maintains drilling of the wellbore along a prescribed well path.

What is claimed is:  
     
         1 . A drilling assembly for drilling a wellbore in a subsurface formation, comprising: 
 (a) a drill bit at an end of said drilling assembly;    (b) an upper and a lower force application device in series in the drilling assembly, each said upper and lower force application device alternately maintaining an associated outer slidable housing stationary relatively to the wellbore inside while applying force on the drill bit to continuously drill the wellbore; and    (c) at least one sensor whose measurements are sensitive to movement of the at least one sensor along the wellbore, said at least one sensor carried at least in part by one of said outer housings, said at least one sensor taking measurements downhole during drilling of the wellbore when the housing carrying the at least one sensor is stationary relative to the wellbore inside.    
     
     
         2 . The drilling assembly of  claim 1 , wherein each said upper and lower force application device includes a separate locking device that engages with the wellbore inside to maintain its associated slidable housing stationary.  
     
     
         3 . The drilling assembly of  claim 1 , wherein each force application device is operated by one of (i) a hydraulic power unit, (ii) an electric motor, and (iii) an electromechanical device.  
     
     
         4 . The drilling assembly of  claim 1 , wherein the at least one sensor is selected from a group consisting of (i) a nuclear magnetic resonance sensor (ii) a formation testing device, (iii) a direction measuring device that includes at least one gyroscope, (iv) an acoustic sensor, (v) a gamma ray device, and (vi) a nuclear sensor for determining a property of the formation.  
     
     
         5 . The drilling assembly of  claim 1 , wherein the at least one sensor includes a nuclear magnetic resonance sensor that comprises: 
 (i) a magnet system that induces a static magnetic fluid in the formation surrounding the wellbore;    (ii) a radio frequency antenna that transmits radio frequency signals at a particular frequency normal to the static magnetic field in a region of investigation in the formation; and    (iii) a processor for processing response signals to the radio frequency signals to determine a property of the formation.    
     
     
         6 . The drilling assembly of  claim 1 , wherein the at least one sensor includes a formation testing device.  
     
     
         7 . The drilling assembly of  claim 6 , wherein the formation testing device includes at least one of: 
 (i) a sample collection device that collects a sample of a fluid from the formation when the housing carrying said sample collection device is stationary relative to the wellbore inside; and    (ii) a measurement device that determines a parameter of the formation fluid.    
     
     
         8 . The drilling assembly of  claim 7 , wherein the parameter of formation fluid is selected from a group consisting of (i) an acoustic property of the formation fluid, (ii) pressure, (iii) temperature, (iv) a physical property of the formation fluid, and (v) a chemical property of the formation fluid.  
     
     
         9 . The drilling assembly of  claim 1 , wherein the at least one sensor includes an acoustic measurement-while-drilling device that comprises at least one acoustic transmitter that transmits acoustic signals into the formation and at least one acoustic detector spaced apart from the acoustic detector that detects acoustic signals propagated through the formation, and a signal processing unit that processes the detected signals for determining a parameter of interest.  
     
     
         10 . The drilling assembly of  claim 1  further comprising a steering device downhole of the force application device, said steering device selectively applying force to the wellbore inside to steer the drill bit in a particular direction.  
     
     
         11 . The drilling assembly of  claim 10 , wherein the steering device comprises a plurality of independently controlled ribs, each said rib capable of extending outward from the drilling assembly to apply a different amount of force on the wellbore inside.  
     
     
         12 . The drilling assembly of  claim 10 , wherein the steering device includes a control unit that controls the force applied by each said rib on the wellbore inside to maintain the drilling of the wellbore along a predetermined wellbore path.  
     
     
         13 . The drilling assembly according to  claim 1  further comprising at least one additional sensor that provides measurements relating to the determination of the direction of said drilling assembly relative to a known position.  
     
     
         14 . The drilling assembly according to  claim 13 , wherein the at least one additional sensor includes at least one of (i) an inclinometer, (ii) a gamma ray device, (iii) a magnetometer, (iv) an accelerometer, and (v) gyroscopic device.  
     
     
         15 . The drilling assembly of  claim 1  further comprising a coupling device that selectively enables coupling and decoupling of the drilling assembly to a rotating member.  
     
     
         16 . A drilling assembly for drilling a wellbore in a subsurface formation, comprising: 
 (a) a drill bit at an end of said drilling assembly;    (b) a force application device capable of continuously applying force on the drill bit to move the drill bit in the wellbore to drill said wellbore; and    (c) a slidable assembly uphold of the force application device having a slidable drill collar, said drill collar having a locking device, wherein the locking device engages the drill collar with the wellbore inside to maintain the drill collar stationary relative to the wellbore while the force application device travels a predetermined distance from an initial position in the wellbore and thereafter disengages from the wellbore inside and allows the drill collar to move toward the force application device by the predetermined distance.    
     
     
         17 . The drilling assembly of  claim 16 , wherein the force application device includes a traction device that continuously moves toward the drill bit while being engaged with the wellbore wall to continuously apply force on the drill bit.  
     
     
         18 . The drilling assembly of  claim 16 , wherein the traction device includes a plurality of continuous motion rollers that engage with the wellbore inside to provide traction force to the drilling assembly.  
     
     
         19 . The drilling assembly of  claim 16 , wherein the force application device is operated by one of (i) a hydraulic power unit, (ii) an electric motor, and (iii) an electromechanical device.  
     
     
         20 . The drilling assembly of  claim 16  further comprising at least one sensor whose measurements are sensitive to movement of the sensor in the wellbore, said at least one sensor being carried at least in part by the drill collar, said at least one sensor taking measurements downhole during drilling of the wellbore when the drill collar portion is stationary relative to the wellbore.  
     
     
         21 . The drilling assembly of  claim 20 , wherein the at least one sensor is selected from a group consisting of (i) a nuclear magnetic resonance sensor (ii) a formation testing device, (iii) a direction measuring device that includes at least one gyroscope, (iv) an acoustic device, and (v) a gamma ray device.  
     
     
         22 . The drilling assembly of  claim 20 , wherein the at least one sensor includes a nuclear magnetic resonance sensor that comprises: 
 (i) a magnet system that induces a static magnetic field in the formation surrounding the wellbore;    (ii) a radio frequency antenna that generates radio frequency signals at a particular frequency normal to a portion of the static magnetic field in a region of investigation in the formation; and    (iii) a processor that processes signals responsive to the radio frequency signals to determine a characteristic of the formation.    
     
     
         23 . The drilling assembly of  claim 20 , wherein the at least one sensor includes a formation testing device to provide measurements for a property of the formation fluid.  
     
     
         24 . The drilling assembly of  claim 23 , wherein the property of the fluid is selected from a group consisting of (i) an acoustic property of the collected sample, (ii) pressure, (iii) temperature, (iv) a physical property of the collected sample, and (v) a chemical property of the collected sample.  
     
     
         25 . The drilling assembly of  claim 16  further comprising a steering device downhole of the force application device, said steering device selectively applying force to the wellbore inside to steer the drill bit in a preselected direction.  
     
     
         26 . The drilling assembly of  claim 25 , wherein the steering device comprises a plurality of independently controlled ribs, each said rib capable of extending outward from the drilling assembly to apply a different amount of force on the wellbore inside.  
     
     
         27 . The drilling assembly of  claim 26 , wherein the steering device includes a control unit that controls the force applied by each said rib on the wellbore inside to maintain the drilling of the wellbore along a predetermined wellbore path.  
     
     
         28 . The drilling assembly of  claim 16 , wherein the drill collar portion slides over a piston disposed inside the drilling collar portion.  
     
     
         29 . The drilling assembly of  claim 16  further comprising a coupling device that enables a drill pipe connected to the drilling assembly to engage with and disengage from a rotating member.