Measurement While Drilling (MWD)

Measurement While Drilling (MWD) applications involve the sending of measurements made by instruments located at the bottom of the hole back to the surface to allow the driller to understand parameters such as the location and orientation of the drill bit. Traditional MWD systems transmit information to the surface by sending pressure pulses through the drilling fluids or wire transmission. Electromagnetic (EM) systems send information to the surface through the earth’s crust utilizing low frequency electromagnetic waves.

The EM Signal always tries to return to the opposite side of the Gap Sub. As the EM Signal travels up the Drill Pipe it leaks off through the surrounding formations and returns to the opposite side of the Gap Sub. The objective is to get enough signal to the surface so that it can be detected by the Surface Amplifier.

MWD Tool Applications

Since the MWD tool’s EM transmission is continuous, survey data can be transmitted during connections resulting in considerable savings in rig time. EM systems are the preferred MWD strategy in many applications, including:

• Under-Balanced Drilling
• Coal Bed Methane (CBM)
• Under-Pressured Formations
• Lost Circulation
• Vertical Control Drilling
• Directional Drilling
• Horizontal Drilling
• Re-entry Wells
• Contaminated Mud Systems

Features / Benefits

Through many years of field tests and design enhancement, the EM MWD offers many key advantages over more traditional MWD systems, such as:

• Programmable to meet local field conditions
• Variable data transmission speeds
• Separate steering and survey frames
• Compact and battery powered
• Key data points including:
  • Magnetic/Gravity Tool Faces
  • Inclination
  • Azimuth
  • Gamma (Directional & 360º) and Annulus Pressure
• Electronic design eliminating mechanical parts
• Does not require pump pressure
• Data output in standard WITS format
• Can be used with a variety of tubular sizes
• EM MWD will work in a variety of fluid conditions such as:
  • Aerated mud
  • While pumping LCM material

Through continued consultation with our customers and suppliers Wellserv EM MWD systems are always evolving operational flexibility, efficiency and intelligence.