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Measurement While Drilling (MWD) - QA/QC

This article describes the the QA/QC tests for Measurement While Drilling (MWD).

1. Surface Function Test

The MWD tool shall be function tested at surface according to contractor procedures.

Two tools should be prepared to ensure a back-up is ready in case the surface circulating test fails.

444 mwd 2Make-up and Alignment of Measurement While Drilling (MWD) to Motor/Bent Sub

When making up the Measurement While Drilling (MWD), align the scribe mark on the motor or bent sub to that on the MWD.

Note: The toolface offset shall be recorded by the Directional Driller who shall supervise the operation.

Circulation

Circulate directly above the Measurement While Drilling (MWD) with the bit and motor made up at the planned flow rate, and record pressure versus flow rate and check performance of the tool.

Gravitational Field Readings

Check the total gravitational field readings which should be close to unity.

2. Survey Benchmarking

Benchmark Criteria

A benchmark survey in open hole should be taken at a suitable survey station at least 100 ft below the previous casing shoe to avoid magnetic interference.

The survey inclination should be within 0.5º of the survey originally recorded at this station, and the survey azimuth should agree within 2º (for survey stations above 10º inclination).

Benchmark surveys should be repeated at the final survey station of the previous bit run prior to drilling ahead.

If the benchmark survey does not meet the above criteria, work the pipe and check the survey again at this or the previously surveyed station.

Repeatability of Benchmark Results

Repeatability of benchmark survey results is prone to variance below 10º of hole inclination.

BHA centralisation, borehole anomalies, washouts and deformations could be the cause of lack of repeatability.

In the event of failure to meet the benchmarking acceptance criteria the Drilling Engineer shall advise further actions.

3. Survey Quality Checks

Survey Quality Checks

When the Measurement While Drilling (MWD) tool transmits quality control outputs with every survey, they can be used to validate the quality of the survey and check the correct functioning of the tool.

The level of quality control that is possible with the MWD shall depend on the number of ‘full survey’ stations which have been obtained with the particular MWD tool within the hole section. At least the first, fourth, seventh etc. stations shall be taken in full survey mode.

Reporting Survey Results

The MWD Engineer shall report all survey results as required, while drilling and at end of each well. The report shall include:

  • instrument serial number
  • calibration date
  • relevant long survey quality control outputs
  • details and analysis of any tool malfunctions.

When long survey quality control outputs are obtained Drilling Supervisor/Drilling Engineer shall check that all Raw Magnetic Values should be similar to computer predictions for the date and location (provided by the Measurement While Drilling (MWD) service company).