The continuous north finding gyro is suitable for oil borehole trajectory measurement and directional borehole tool face measurement (e.g. sidetrack drilling directional survey). Usually, this survey process will need:
Winch- is equipped with armored cable (usually 8mm single core cable);
Pulley;
Depth counter (usually photoelectric encoder, output phase A and phase B signal, adding and subtracting counting by their phase lead-lag).
When at measurement, the surface equipment supply power and transmit survey signal to down hole probe by cable, the depth counter connect the phase A and B to surface equipment to survey depth.
When start a survey, firstly, the tool need to find north at wellhead, then put it down to bottom with a speed less than 5000m/h for measurement.
Usually the tool can be used directly for oil borehole with inclination <70º(vertical = 0),limitation angle 85º.
For horizontal borehole, need to change survey mode and the survey speed will reduce at this case.
When using the memory mode for oil borehole, usually use the wire rope. The wire rope winch is also equipped with depth counter; the surface host read the depth and relative time, while the down hole probe save survey data with same time interval.
When the survey ends, operator collects the depth-time, time-data corresponding, a depth-data-time survey result will be generated, and then the surface host will make borehole trajectory calculation.
This process is continuous; clients can set up any time interval or depth interval to record survey data.