DIGITAL DOWNHOLE SEISMOGRAPH

The FD301 tester is specifically designed for downhole seismic testing. This tester which satisfies all the requirements of ASTM D-7400, comprises of a probe, a workstation and a winch. This integrated portable solution allows engineers to efficiently and easily operate the system optimally for the downhole seismic test. This is not the case with conventional seismographs in which fragmented hardware such as multi-input chanels and various analog probes are used. The FD301 probe includes three geophone sensors with sensitivities both to P and S waves. The acquired P and S wave signals are pre-amplified and digitized inside the probe at their reception, and then sent over an RS485 link via a 50m (100m optional) cable. Integration of pre-amplifiers and digitizing circuits inside the probe improves signal to noise ratio. This makes the system highly sensitive to mechanical waves and enables the tester to operate over a wider range of environmental and ground conditions. Viewing the test results and reporting is easily possible using the workstation embedded rugged industrial computer; so there is no need for connecting a laptop or desktop computer to the system as common in other products. The P & S signals are displayed on the workstation monitor, facilitating the user with powerful data visualization tools. Dedicated designed software helps with editing and post processing the captured signals.l

A winch is used to collect and carry the system cable to ease system set up and usage. This winch is equipped with a slip ring which eliminates the need for un-wrapping the whole cable in each test. The user can connect the free end of the cable to the probe and send it inside the bore at desired depth. The other end of the cable is fixed to the winch and can be connected to the workstation via a 2 meters cable. Perfect packing of the probe to the bore wall is a key issue in capturing weak mechanical vibrations and performing a high quality downhole test. This is best achieved by designing a built-in electromechanical anchor in FD301 probe. This anchor can be opened and closed simply by sending the commands via the system software. Using the electromechanical packing technic eliminates the problems introduced by the conventional air cushion packers. The system power is provided by a sealed acid battery which is embedded inside the system workstation. This battery can be charged using mains AC power line or by a vehicle battery. The whole system can also be operated by simple connection to a conventional vehicle battery.d