Measurement While Drilling

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  • Topic: Petroleum, Oil well, Drilling technology
  • Pages : 10 (2751 words )
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  • Published : April 21, 2013
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measurement wild drilling

MWD stands for Measurement While Drilling in the oil & gas industry. The simplest way to describe MWD is to relate it to the measurements a pilot takes. A pilot needs to know the direction they are flying (North, South, East, or West), the angle they are flying at (up, down, or horizontal), and what type of skies they will be flying through (rough, choppy, cloudy, rainy, etc.). Like a pilot a directional driller needs to know these items about the ground formations that they are drilling through. MWD provides this information. Previous to MWD measurements were taken at various parts of the drilling process, but MWD has allowed these measurements to be sent to the surface continuously while the hole is being drilled. This allows for faster drilling, more accurate drilling, and safer drilling. Beyond the basic concept MWD is a system developed to perform drilling related measurements downhole that are transmit to the surface while drilling a well. MWD tools are installed as part of the bottom hole assembly (BHA) near the drill bit. The tools are either contained inside a thick walled, drill collar (drill collars are typically used to add weight for drilling) or they are built directly into the collars at a factory prior to arriving on the drilling location. MWD systems can take several measurements such as Gamma Ray, compass direction (shown as azimuth), tool face (the direction that your bit is pointing), borehole pressure, temperature, vibration, shock, torque, etc. The MWD also provides the means of communication for operating rotary steering tools (RSTs). The measured results are stored in MWD tools and some of the results can be transmitted digitally to surface using mud pulser telemetry through the mud or other advanced technology such as electromagnetic(EM) frequency communications or wired drill pipe. Contents * 1 Types of information transmitted * 1.1 Directional information * 1.2 Drilling mechanics information * 1.3 Formation properties * 2 Data transmission methods * 2.1 Mud pulse telemetry * 2.2 Electromagnetic telemetry (EM Tool) * 2.3 Wired Drill Pipe * 3 Retrievable tools * 3.1 Limitations * 4 References * 5 See also| -------------------------------------------------

[edit]Types of information transmitted
[edit]Directional information
MWD tools are generally capable of taking directional surveys in real time. The tool uses accelerometers and magnetometers to measure the inclination and azimuth of the wellbore at that location, and they then transmit that information to the surface. With a series of surveys; measurements of inclination, azimuth, and tool face, at appropriate intervals (anywhere from every 30 ft (i.e. 10m) to every 500 ft), the location of the wellbore can be calculated. By itself, this information allows operators to prove that their well does not cross into areas that they are not authorized to drill. However, due to the cost of MWD systems, they are not generally used on wells intended to be vertical. Instead, the wells are surveyed after drilling through the use of Multishot Surveying Tools lowered into the drillstring on slickline or wireline. The primary use of real-time surveys is in Directional Drilling. For the Directional Driller to steer the well towards a target zone, he must know where the well is going, and what the effects of his steering efforts are. MWD tools also generally provide toolface measurements to aid in directional drilling using downhole mud motors with bent subs or bent housings. For more information on the use of toolface measurements, see Directional Drilling. [edit]Drilling mechanics information

MWD tools can also provide information about the conditions at the drill bit. This may include: * Rotational speed...
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