What is the difference between MWD and LWD ?

I’m still new to the oil field,but here is what I know MWD gives real time data which we call (RT), this data includes only surveies such as the inclination of the well and azimuth, and MWD tool may also include gamma ray. LWD gives recorded data, which means that the data will be saved in the tool and later when the tool is out of the hole they do something called dumping to get the information,LWD usually includes gamma ray,resistivity and porosity logs.

With LWD you have many more details on drilling environment and formation. You can measure vibrations to avoid waste of energy and misuse or fail  of your BHA, pressures (internal on drill string and annular) so you can manage and improve drilling, gauge and caliper the well on real timel, and off course the direction and inclination of the well.

 

As for formation you have tools that can mesaure all petrophyics characteristisc directly or indirectly. The mais measures are gamma ray, resistivity, slowness (sonic), porosity and density. Mora advanced tools also measure pore pressure and perform a "while drilling well test" measuring drawndown and build ups. Some of this tools may even colect samples of fluid as soon as a particluar section of the well is drilled preserving better reservoir conditions and giving more accurate data.

MWD - meausure while drilling (inclination, azimuth, depth - DIRECTION), LWD - logging while drilling - getting information about formation type, with applying different environmental corrections