Survey apparatus and methods for directional wellbore surveying

A method of conducting an oil well survey along a well borehole comprising the steps of:

• (a) moving an elongate drill collar having an axis coincident along a well borehole between first and second selected positions to form a survey connected between first and second positions wherein said first position is located within a non vertical section of said well borehole;
• (b) positioning a rate gyro in said drill collar wherein said rate gyro forms output signals indicative of measured angular rate at said first and second positions;
• (c) positioning in said drill collar first and second accelerometers at a right angle therebetween wherein said accelerometers define a transverse plane to the axis of said collar, and forming outputs from said first and second accelerometers indicative of values sensed thereby at said first and second positions in said well borehole and relative to a reference inclination;
• (d) converting data representative of the outputs of said rate gyro and said accelerometers including said first and second positions along the well borehole to determine well borehole inclination;
• and
• (e) recording a plot of well borehole inclination to form a plot through said first and second positions.

A method of conducting an oil well survey along a well borehole comprising the steps of:

• (a) moving an elongate drill collar having an axis coincident therewith along a well borehole to first and second selected positions to form a survey at said first and second positions, wherein inclination of said well borehole at said first position is greater than about 15 degrees;
• (b) positioning a rate gyro in said drill collar wherein said rate gyro forms output signals indicative of measured angular rate at said first and second positions;
• (c) positioning in said drill collar first and second accelerometers at a right angle therebetween wherein said accelerometers define a transverse plane to the axis of said drill collar;
• and forming outputs from said first and second accelerometers indicative of values sensed thereby at first and second positions in said well borehole with respect to a reference inclination at said first position;
• (d) forming stored data representative of the outputs of said rate gyro with respect to a reference azimuth at said first position and said accelerometers at said first and second positions along the well borehole to determine well borehole azimuth and inclination;
• and
• (e) recording a plot of well borehole azimuth and inclination at said first and second positions.

A method of conducting an oil well survey along a well borehole comprising the steps of:

• (a) moving an elongate sensor along a well borehole at first and second selected positions to form a survey at said first and second positions, wherein inclination of said well borehole at said first position is greater than about 15 degrees;
• (b) positioning a rate gyro in said sensor wherein said rate gyro forms orthogonal output signals indicative of measured angular rate between said first and second positions;
• (c) positioning in said sensor first and second accelerometers at a right angle therebetween wherein said accelerometers define a transverse plane to the axis of said sensor;
• (d) measuring a reference azimuth and a reference inclination at said first position and computing and storing data representative of the outputs of said rate gyro relative to said reference azimuth and said accelerometers relative to said reference inclination at said first and second positions along the well borehole;
• and
• (e) converting the stored data into a plot of well borehole azimuth at said first and second positions.

An apparatus comprising:

• (a) an elongate drill collar having an axis along the length thereof;
• (b) a motor in a housing for rotating a shaft extending along said collar;
• (c) a rate gyro supported by said collar and axially aligned within said collar and connected to said shaft for rotation thereby;
• (d) a pair of accelerometers defining an X and Y plane wherein said pair are at right angles, and are rotated by said motor shaft;
• (e) a signal processor connected to said rate gyro and said pair of accelerometers to process signals therefrom to form a survey of a well borehole, wherein said signal processor
• (i) forms a ratio of X and Y components of outputs of said accelerometers projected onto said X and Y planes, and
• (ii) combines X and Y outputs from said rate gyro with a function of said ratio thereby correcting said ratio for any non gravity acceleration effects and yielding a relative borehole inclination;
• and
• (f) a control for said signal processor to start operation thereof so that said processor forms a survey at first and second locations in said well borehole, wherein inclination of said well borehole at said first location is greater than about 15 degrees.

A method of conducting an oil well survey along a well borehole comprising the steps of:

• (a) moving an elongate sensor along a well borehole at first and second selected positions to form a survey at said first and second positions, wherein said first position is located within a non vertical section of said well borehole;
• (b) positioning a rate gyro in said sensor wherein said rate gyro forms orthogonal output signals indicative of measured angular rate at said first and second positions;
• (c) positioning in said sensor first and second accelerometers at a right angle therebetween wherein said accelerometers define a transverse plane to the axis of said sensor;
• (d) measuring gravity induced signals from said first and second accelerometers at the first position and determining therefrom a vector component describing the first position wherein the component includes well borehole inclination;
• (e) measuring at the first position a vector component describing sensor azimuth;
• (f) moving the sensor along the well borehole to the first and a second position in the well borehole;
• (g) storing data representing the inclination and azimuth at first and second positions;
• (h) measuring a reference azimuth and a reference inclination at said first position and computing and storing data representative of the output of said rate gyro relative to azimuth;
• (i) storing data representative of said accelerometers relative to inclination;
• and
• (j) converting the stored data into a plot of well borehole azimuth at said first and second positions.

A method of conducting an oil well survey along a well borehole comprising the steps of:

• (a) moving an elongate sensor along a well borehole at first and second selected positions along the well borehole to form a borehole survey at said first and second positions, wherein said first position is located within a non vertical section of said well borehole;
• (b) measuring angular rate of the sensor on movement between said first and second positions;
• (c) placing first and second accelerometers at a right angle in said sensor wherein said accelerometers define a transverse plane to axis of said sensor;
• (d) measuring gravity induced signals from said first and second accelerometers at the first and second positions;
• (e) determining the well borehole inclination;
• (f) determining a vector component describing sensor azimuth;
• (g) moving the sensor along the well borehole to the first and a second position in the well borehole;
• (h) storing data representing the inclination and azimuth at said first and second positions;
• and
• (i) converting the stored data into a plot of well borehole azimuth at said first and second positions.

A method of conducting an oil well survey comprising the steps of:

• (a) positioning a sensor in a well borehole to conduct a survey;
• (b) positioning a gyro in said sensor wherein said gyro forms orthogonal output signals responsive to gyro operation with sensor movement along said well borehole movement;
• (c) positioning two orthogonal accelerometers in a plane traverse to said sensor to form accelerometer output signals;
• (d) defining from said orthogonal accelerometer signals tool high side at a first time, wherein said sensor is located within a non vertical section of said well borehole at said first time;
• (e) determining at the first time the position of the gyro as indicated by the output signals of the gyro;
• and
• (f) moving the sensor along the well borehole from the first time to a second time and determining between said first and second times rotation of the sensor around an axis along the well borehole in response to said output signals.