The Measurement While Drilling is an essential service to guide the BHA to hit the target as per directional well plan by communicating continuously and every tool joint survey to surface. The MWD tool communicate also temperature, shocks, DHWOB, DHTOR and annular pressure (if sensors installed), the most important part in the MWD tool is the Pulser which is the mud pressure telemetry to communicate with surface collected by the pressure sensor. (Different telemetry types also are available like Electromagnetic or by the wired Drill pipes). At the preparation phase the engineer need to have all information to make the right setting in the tool:
- Final Hole depth
- Pump configuration (Number of pistons, ID, length, flow rate, Dumpners pressure)
- BHA components.
- Available place in the standpipe.
- Maximum static temperature as per the offset well.
- Modulator gap.
- Modulator size.
- Modulator flow rang.
- Sensors temperature rang.
- Required sensors.
- Oil type.
- Collar size.
- Software upgrade.
Conventionally the natural Gamma Ray sensor can be add to the probe as per client requirement, this sensor should be calibrated as per API standard.
It’s important to calibrate the Directional and Inclination sensor and also follow the tendency of the BIAS if remains in rang to predict the failure and avoid sending for operation.
The Multi-Shot service is the D&I service in recorded mode without Pulser telemetry module. Some client may request inclination only; others may require both inclination and azimuth measurements to be provided:
Inclination Services Only
The client normally request the “inclination – only” service whenever, they need to have an inclination check – shot survey. This is normally performed at vertical wells. The Probe can sent downhole using wireline or inside the none Magnetic DC, in this case it should be placed a small sub or UBHO where we will place a Totco Ring or a orientation sleeve for the UBHO, where the probe will be seated. Once the probe tags the bottom of the BHA or gets the lower depth inside the BHA while the BHA tags bottom, the probe is pulled out on wireline.
Direction and Inclination Services
The direction and Inclination (D&I) service is normally required whenever the client wants to have a check shot surveys taken on a well that does not use an MWD tool. Enough nonmagnetic drill collars must be used in the BHA in order to record accurate azimuthal measurements. For this service the tool will remain in the BHA while tripping out of hole. There also needs to be enough stationary time at each survey station, and an accurate time and depth should be also recorded.