GeoVista - Memory Logging Systems

Geovista memory logging systems allow users to run selected GeoVista probes without the need for a logger or a logging winch. The log parameters are uploaded and the recorded data is downloaded by the user, by means of a field tablet and the Geovista Android app. The downloaded logging and depth data are merged to produce the equivalent of a traditional log against depth.

A typical system would include the following:

• A depth measuring assembly (*)
• A depth-time recorder (DTR) unit
• A battery £) &_
• A memory module
• Any applicable running gear
• A field tablet

If the rig wireline is used to convey the downhole tools while logging, a depth encoder wheel assembly is used to measure depth. In the case of logging while tripping out, a laser ranging device is used to track the travel of the drill head (and pipe). This is typically mounted on the rig mast. In this case, a sensor must be fitted to detect whether the foot clamp is engaged or not.

In-rod logging
Applications for in-rod memory logging include gyro surveys, natural gamma, and density logging. Density logging while tripping out reduces the requirement for corrections as the tool remains in the same position in the drilling rod.

Through-bit logging

This technique is useful highly inclined, or unstable cored boreholes. Once the borehole is ready for logging, the drill rods are pulled off bottom far enough to accommodate the logging tool string. The memory system is activated and synchronised before the logging tools are lowered down using the rig`s wireline spear and overshot system that is used to convey the core sleeve.

The running gear is arranged in a way that when the landing ring sits on top of the coring bit, the logging tools stick out into the open borehole. The borehole is the logged as the drill rods are tripped out.