MWD (Measurement While Drilling) is a system developed to perform drilling related measurements downhole and transmit information to the surface while drilling a well.
The Measurement While Drilling (MWD) Tool came in to application in early 1970’s.
Before the introduction of MWD, all survey data were obtained by stopping the drilling process for wireline logging. For wireline logging, we had to stop the drilling process, put the drill pipe on slip, break out Kelly, lower the wireline tool, retrieve the tool, read the survey and plan the further action. This used to increase the non productive time (NPT).
The MWD tool transmitted the survey reading to surface through the mud stream in the drill pipe. The drilling process was stopped for few minutes and survey readings were obtained in pump off condition. This saved times to greater extent compared to wireline logging.
The transmission of survey data though mud stream was one of the means. Other means of transmission were electromagnetic and acaustic which were developed in later stages.
Thus MWD was considered a better option for survey data transmission compared to wireline procedure.
