Well logging, the concept of formation evaluation through a borehole, began nearly 90 years ago with a simple measurement of resistivity. A cable was lowered to the borehole with electrodes to measure the resistivity of the formation. Electrical current was sent from the surface, and then voltage between two electrodes was measured at the surface. In other words, there was no "data transmission." With the advancement of measurements, various analog transmission methods were used (pulse, AM, FM, etc.). However, analog methods of data transmission proved to be inadequate for further advancement. Not only was the number of tools that could be connected in one run limited, the signals would be distorted when received at surface, not delivering the required resolution in the measurements. Thus, dedicated digital telemetry systems came to wireline operations to reliably send the measurements to surface in the late 1970s.

Recently, Schlumberger deployed its fastest wireline telemetry system to the field and since then has witnessed a great improvement in the service delivery to the customer. Faster data handling capabilities of the latest telemetry system have enabled logging of multiple tools in a single run at faster logging speeds. One example is that it removes the previous limitation of logging speed of the sonic tool when all mode of waveforms are acquired, such as compressional, shear, Stoneley, radial profiling and borehole acoustics reflection survey. This brings reduces rig time, which brings a substantial cost advantage, especially in deepwater exploration wells. Another service that hugely benefits from improved telemetry is the hydraulic fracture monitoring of microseismic events. We are now able to perform high-resolution sampling at 20 levels, providing a more comprehensive picture of what is happening in the rock strata.

At a time when our industry is focused not only on the quality of the measurements, but also the efficiency at which the measurements can be delivered and made available to the customers, advanced telemetry systems are an enabling technology. Telemetry systems ensure that all measurements are reliably sent to surface, where complex algorithms are then able to process these data and deliver valuable answer products to the customer.

This content is only available via PDF.
You can access this article if you purchase or spend a download.