Whipstock assembly

Abstract

A whipstock assembly ( 12 ) for use in deviating a wellbore ( 10 ) of a well is disclosed, the whipstock assembly comprising a whipstock ( 18 ) having an inclined deflection surface ( 20 ); a milling assembly ( 14 ) comprising a mill ( 16 ) for milling a window ( 49 ) in a wall ( 48 ) of the wellbore and forming a rathole ( 50 ) extending from the wellbore; a releasable joint ( 22; 122 ) by which the milling assembly is releasably connected to the whipstock, so that the milling assembly can be separated from the whipstock within the wellbore and subsequently deflected towards the wellbore wall by the deflection surface of the whipstock; at least one sensor ( 188 ) provided in the milling assembly, for measuring at least one parameter of the rathole, the at least one parameter relating to a trajectory of the rathole; and a communication device ( 190 ) associated with the at least one sensor, for communicating data relating to the at least one parameter to an operator of the milling assembly.

1 . A whipstock assembly for use in deviating a wellbore of a well, the whipstock assembly comprising:
 a whipstock having an inclined deflection surface;   a milling assembly comprising a mill for milling a window in a wall of the wellbore and forming a rathole extending from the wellbore;   a releasable joint by which the milling assembly is releasably connected to the whipstock, so that the milling assembly can be separated from the whipstock within the wellbore and subsequently deflected towards the wellbore wall by the deflection surface of the whipstock;   at least one sensor provided in the milling assembly, for measuring at least one parameter of the rathole, the at least one parameter relating to a trajectory of the rathole; and   a communication device associated with the at least one sensor, for communicating data relating to the at least one parameter to an operator of the milling assembly.   
     
     
         2 . A whipstock assembly as claimed in  claim 1 , in which the at least one sensor is selected from the group comprising: an inclination monitoring sensor for monitoring an inclination of the rathole; and an azimuth monitoring sensor for monitoring an azimuth of the rathole. 
     
     
         3 . A whipstock assembly as claimed in  claim 1 , in which at least one sensor is provided which is for monitoring a milling parameter. 
     
     
         4 . A whipstock assembly as claimed in  claim 3 , in which the at least one sensor is selected from the group comprising: a vibration monitoring sensor; a shock monitoring sensor; and a sensor for measuring one or more of rotation, torque and weight of or on the mill. 
     
     
         5 . A whipstock assembly as claimed in  claim 1 , in which at least one sensor is provided which is for measuring at least one formation parameter, the parameter selected from the group comprising gamma ray/radiation, porosity and density. 
     
     
         6 . A whipstock assembly as claimed in  claim 1 , comprising a mounting unit containing the at least one sensor and the communication device, the mounting unit being releasably mountable to a component of the milling assembly. 
     
     
         7 . A whipstock assembly as claimed in  claim 6 , in which the mounting unit comprises a housing containing the at least one sensor and the communication device, the housing being releasably mountable to the milling assembly component. 
     
     
         8 . A whipstock assembly as claimed in  claim 7 , in which the housing comprises a housing body containing the at least one sensor and the communication device, and a housing cap which is sealingly mountable to the housing body. 
     
     
         9 . A whipstock assembly as claimed in  claim 1 , in which the releasable joint comprises a first part mounted to the milling assembly and a second part mounted to the whipstock. 
     
     
         10 . A whipstock assembly as claimed in  claim 9 , in which the releasable joint is a shear bolt, one of the first and second parts being a bolt portion, and the other one of the first and second parts being a head portion, a shear zone being provided on the head portion which, on shearing, separates the joint into a first section comprising a part of the head portion and a second section comprising a further part of the head portion and the bolt portion. 
     
     
         11 . A whipstock assembly as claimed in  claim 1 , in which the at least one sensor and the communication device are mounted within the releasable joint. 
     
     
         12 . A whipstock assembly as claimed in  claim 11 , in which the releasable joint comprises a first part mounted to the milling assembly and a second part mounted to the whipstock, and in which the at least one sensor and the communication device are mounted within the first part of the releasable joint. 
     
     
         13 . A whipstock assembly as claimed in  claim 12 , comprising a mounting unit containing the at least one sensor and the communication device, the mounting unit being releasably mountable within the first part of the releasable joint. 
     
     
         14 . A whipstock assembly as claimed in  claim 1 , in which the at least one sensor and the communication device are mounted within the mill. 
     
     
         15 . A whipstock assembly as claimed in  claim 14 , comprising a mounting unit containing the at least one sensor and the communication device, the mounting unit being releasably mountable within the mill. 
     
     
         16 . A whipstock assembly as claimed in  claim 14 , in which:
 the mill is a starter mill provided at a leading end of the milling assembly;   the milling assembly comprises at least one window mill which is spaced along the assembly from the leading end; and   at least one sensor and communication device are mounted within each of the starter mill and the at least one window mill.   
     
     
         17 . A whipstock assembly as claimed in  claim 1 , in which the milling assembly comprises at least one stabiliser, and in which the at least one sensor and the communication device are mounted within the stabiliser. 
     
     
         18 . A whipstock assembly as claimed in  claim 17 , comprising a mounting unit containing the at least one sensor and the communication device, the mounting unit being releasably mountable within the stabiliser. 
     
     
         19 . A whipstock assembly as claimed in  claim 17 , in which the milling assembly comprises a plurality of stabilisers, and in which at least one sensor and communication device are mounted within each stabiliser. 
     
     
         20 . A whipstock assembly as claimed in  claim 1 , comprising a source of power for providing power to operate the at least one sensor and the communication device, in which the power source is provided in the milling assembly. 
     
     
         21 . A whipstock assembly as claimed in  claim 20 , comprising a mounting unit comprising a housing containing the at least one sensor and the communication device, the housing being releasably mountable to the milling assembly, and in which the housing contains the power source. 
     
     
         22 . A whipstock assembly as claimed in  claim 1 , comprising a data storage device associated with the sensor for storing the data, the data storage device being provided in the milling assembly. 
     
     
         23 . A whipstock assembly as claimed in  claim 22 , comprising a mounting unit comprising a housing containing the at least one sensor and the communication device, the housing being releasably mountable to the milling assembly, the housing containing the data storage device. 
     
     
         24 . A whipstock assembly as claimed in  claim 22 , in which the communication device comprises a communication interface associated with the data storage device, for receiving the data. 
     
     
         25 . A whipstock assembly as claimed in  claim 24 , in which the communication device comprises a data transmitter for transmitting data to the operator, the data transmitter being associated with the communication interface for receiving data from the data storage device. 
     
     
         26 . A whipstock assembly as claimed in  claim 24 , in which the communication interface is adapted to be connected to a further data interface so that the data can be downloaded. 
     
     
         27 . A releasable joint for releasably connecting a milling assembly to a whipstock, the releasable joint comprising:
 a first part adapted to be mounted to the milling assembly;   a second part adapted to be mounted to the whipstock;   a shear zone adapted to shear on application of a predetermined load, to separate the first part from the second part and so disconnect the milling assembly from the whipstock;   at least one sensor for measuring at least one parameter of a well; and   a communication device associated with the at least one sensor, for communicating data relating to the at least one parameter to an operator of the milling assembly;   in which the at least one sensor and the communication device are provided in the first part of the releasable joint.   
     
     
         28 . (canceled) 
     
     
         29 . (canceled) 
     
     
         30 . A method of deviating a wellbore of a well and verifying a trajectory of the deviation, the method comprising the steps of:
 connecting a milling assembly to a whipstock using a releasable joint, to form a whipstock assembly comprising the milling assembly and the whipstock;   deploying the whipstock assembly into the wellbore;   positioning the whipstock at a desired location within the wellbore and subsequently disconnecting the milling assembly from the whipstock by releasing the releasable joint;   translating the milling assembly within the wellbore in a direction towards the whipstock, so that a mill of the milling assembly is deflected towards a wall of the wellbore by a deflection surface of the whipstock;   activating the mill to form a window in the wall of the wellbore, and subsequently forming a rathole extending from the wellbore;   operating at least one sensor provided in the milling assembly whilst the milling assembly is located in the rathole to measure at least one parameter of the rathole, the at least one parameter relating to a trajectory of the rathole; and   communicating data relating to the at least one parameter to an operator via a communication device associated with the at least one sensor, so that the trajectory of the rathole can be verified.