Logging While Drilling

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Logging While Drilling is a technique of measuring geological formation properties in real-time while drilling an oil well.

1 Description
- 1.1 Measured parameters
2 References
3 See also

[edit] Description

Logging While Drilling (LWD), along with "Measurement While Drilling" (MWD) systems provide wellbore directional surveys, petrophysical well logs, and drilling information in real-time while drilling. MWD refers to measurements acquired down hole while drilling that specifically describe directional surveying and drilling-related measurements. LWD refers to petrophysical measurements, similar to open hole wireline logs, acquired while drilling. These systems are based on mud telemetry (mud pulse), where variations in pressure exercised by the tool can be sensed on the surface via a computer or Electromagnetic telemetry, and thus communication is established.

[edit] Measured parameters

A suite of tools record different parameters of the drilled rocks:

Natural Gamma Ray (GR)
- Average Gamma Ray
- Gamma Ray Spectrometry (Potassium, Thorium, Uranium)
- Focused Gamma Ray + 360° images
Electric
- Spontaneous Potential (old)
- Resistivity (Phase Shift & Attenuation)
  - Focusing electrode logs (Laterolog devices) + 360° images
  - Induction logs
Density & Porosity
- Bulk density logs + 360° images
- Neutron Porosity
- Neutron Gamma Spectroscopy
- Thermal Neutron Decay time
- PhotoElectric Factor
- Ultra Sonic Caliper + 360° images
- ...
Nuclear Magnetic Resonance (NMR)
- Porosity
- Permeability
- Free and Bound Fluids
- ...
Acoustic (Sonic) response
- Compressional Slowness (Δtc)
- Shear Slowness (Δts)
- Estimated Porosity
- ...
Seismic While Drilling (SWD)
- Drillbit-SWD
- VSP-WD (Vertical Seismic Profile While Drilling)
Formation Pressure
- Fluid type
- Permeability
- ...