Logging While Drilling
Encyclopedia
Logging While Drilling is a technique of conveying well logging tools
into the well borehole downhole as part of the bottom hole assembly
(BHA).
LWD tools work with its Measurement While Drilling (MWD) system to transmit partial or complete measurement results to the surface via typically a drilling mud pulser or other improved techniques, while LWD tools are still in the borehole, which is called "Real Time Data". Complete measurement results can be downloaded from LWD tools after they are pulled out of hole, which is called "Memory Data".
LWD technology was developed originally as an enhancement to the earlier MWD
technology to completely or partially replace wireline logging operation. With the improvement of the technology in the past decades, LWD is now widely used for drilling (including geosteering
), formation evaluation
(especially for real time and high angle wells).
Well logging
Well logging, also known as borehole logging is the practice of making a detailed record of the geologic formations penetrated by a borehole. The log may be based either on visual inspection of samples brought to the surface or on physical measurements made by instruments lowered into the hole...
into the well borehole downhole as part of the bottom hole assembly
Bottom hole assembly
A Bottom hole assembly is a component of a drilling rig. It is the lower part of the drill string, extending from the bit to the drill pipe. The assembly can consist of drill collars, subs such as stabilizers, reamers, shocks, hole-openers, and the bit sub and bit.-Variations:The bottom-hole...
(BHA).
LWD tools work with its Measurement While Drilling (MWD) system to transmit partial or complete measurement results to the surface via typically a drilling mud pulser or other improved techniques, while LWD tools are still in the borehole, which is called "Real Time Data". Complete measurement results can be downloaded from LWD tools after they are pulled out of hole, which is called "Memory Data".
LWD technology was developed originally as an enhancement to the earlier MWD
Measurement While 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 , the angle they are fly at , and what type of skies they will be flying through...
technology to completely or partially replace wireline logging operation. With the improvement of the technology in the past decades, LWD is now widely used for drilling (including geosteering
Geosteering
In the process of drilling a borehole, geosteering is the act of adjusting the borehole position on the fly to reach one or more geological targets...
), formation evaluation
Formation evaluation
In petroleum exploration and development, formation evaluation is used to determine the ability of a borehole to produce petroleum. Essentially, it is the process of "recognizing a commercial well when you drill one"....
(especially for real time and high angle wells).
Available LWD Measurements
LWD technology was originally developed to partially or completely replace wireline logging. Over the years, majority of the measurements have been made available in LWD. Certain new measurements are also development in LWD only. The following is an incomplete list of available measurement in LWD technology.- Natural Gamma RayGamma ray loggingGamma ray logging is a method of measuring naturally occurring gamma radiation to characterize the rock or sediment in a borehole. It is sometimes used in mineral exploration and water-well drilling, but most commonly for formation evaluation in oil and gas well drilling . Different types of...
(GR)- Total Gamma Ray
- Spectral Gamma Ray
- Azimuthal Gamma Ray
- Gamma ray close to drill bit.
- Density and Photoelectric Index
- Neutron PorosityFormation evaluation neutron porosityIn the field of formation evaluation, porosity is one of the key measurements to quantify oil and gas reserves. Neutron porosity measurement employs a neutron source to measure the hydrogen index in a reservoir, which is directly related to porosity...
- Borehole CaliperCaliper logA caliper log is a set of measurements of the size and shape of a bore hole commonly made when drilling oil and gas wells. This can be an important indicator of cave ins or shale swelling in the bore hole....
- Ultra sonic azimuthal caliper.
- Density Caliper
- ResistivityResistivity loggingResistivity logging is a method of well logging that works by characterizing the rock or sediment in a borehole by measuring its electrical resistivity. Resistivity is a fundamental material property which represents how strongly a material opposes the flow of electric current...
(ohm-m)- Attenuation and phase shift resistivities at different transmitter spacings and frequencies.
- Resistivity at the drill bit.
- Deep directional resistivitiesjhhi
- SonicSonic loggingSonic logging shows a formation’s interval transit time, designated Dt. It is a measure of a formation’s capacity to transmit sound waves. Geologically, this capacity varies with lithology and rock textures, notably porosity....
- Compressional Slowness(Δtc)
- Shear Slowness (Δts)
- Borehole Images
- Density Borehole Image
- Resistivity Borehole Image
- Formation Tester and SamplerDrill Stem TestA drill stem test is a procedure for isolating and testing the surrounding geological formation through the drill stem. The test is a measurement of pressure behavior at the drill stem and is a valuable way to obtain important sampling information on the formation fluid and to establish the...
- Formation Pressure
- Formation Fluid Sample
- Nuclear Magnetic Resonance (NMR)Nuclear magnetic resonanceNuclear magnetic resonance is a physical phenomenon in which magnetic nuclei in a magnetic field absorb and re-emit electromagnetic radiation...
- Seismic While Drilling (SWD)
- Drillbit-SWD
See also
- GeosteeringGeosteeringIn the process of drilling a borehole, geosteering is the act of adjusting the borehole position on the fly to reach one or more geological targets...
- measurement While DrillingMeasurement While DrillingMWD 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 , the angle they are fly at , and what type of skies they will be flying through...