During drilling operations for extraction of hydrocarbons, a variety of communication and transmission techniques have been attempted to provide real time data from the vicinity of the bit to the surface during drilling. The use of measurements while drilling (MWD) with real time data transmission provides substantial benefits during a drilling operation. For example, monitoring of downhole conditions allows for an immediate response to potential well control problems and improves mud programs.
Measurement of parameters such as weight on bit, torque, wear and bearing condition in real time provides for more efficient drilling operations. In fact, faster penetration rates, better trip planning, reduced equipment failures, fewer delays for directional surveys, and the elimination of a need to interrupt drilling for abnormal pressure detection is achievable using MWD techniques.
Moreover, during a trip out operation, retrieval of data from the downhole tool typically requires a communications cable be connected thereto. The data rate for downloading data from the downhole tool over such cables is typically slow and requires physical contact with the tool. Additionally, a drilling rig operator must be present to connect a communications cable to the downhole tool to download data therefrom. The communications cable and connectors are often damaged by the harsh rig environment. Valuable rig time is often lost by normal cable handling as well as cable repairs. Furthermore, if the downhole tool includes a nuclear source the cable connection and data download cannot be initiated until such source is first safely removed.