| Title | A High Speed, High Temperature Datalink for Geothermal Applications |
|---|---|
| Authors | Lindblom, Scott; Henfling J. A.; Macrae, Andrew; Yeung, Kevin; Baran, Kyle; Fong, Gregory; Qu, Johnson; McAuley, Tynan; Parks, James |
| Year | 2011 |
| Conference | Geothermal Resources Council Transactions |
| Keywords | Data communications; high temperature electronics; high temperature logging tools; logging cable; well logging |
| Abstract | Many phases in the construction of a geothermal well or engineered reservoir are enhanced through the use of tools that provide real time data feedback. Drilling diagnostic tools, seismic monitoring tools, and televiewers are among the tools that can provide this type of feedback. In order to achieve their full potential, these tools require communication rates over 500 kbps along 15,000 feet of single conductor wireline. However, current high temperature wireline communication techniques prevent tools from transmitting at these rates. For example, Sandia’s high temperature televiewer is limited to less than 11 kbps over 15,000 feet of single conductor wireline. In addition, Sandia’s recently developed high temperature seismic tool can transmit at 200 kpbs, but only over multiconductor cables less than 5,000 feet in length. Sandia, in collaboration with Harvey Mudd College, has shown that data rates can be increased by a factor of two with minimal modification to current high temperature downhole electronics. Traditional techniques to increase wireline communication speeds include advanced digital signaling and/or modulation schemes that are difficult to implement with high temperature electronics. Therefore, this new high speed communication system places the majority of the computational burden on the uphole receiver, which can be designed around state-of-the-art electronics. The uphole receiver utilizes a combination of equalization to overcome distortion caused by the wireline and correlation to recover corrupted data to achieve a demonstrated data rate exceeding 400 kbps. This method has the advantage of working over industry standard single conductor wireline with existing high temperature tools. Communication speed can be easily modified for a given application by changing a single crystal oscillator in the downhole electronics. This paper includes details on the methodology of the developed high speed datalink. Design details for both the uphole and the downhole electronics are discussed. Lab tests demonstrating reliable operation up to 400 kbps are also presented. |