Downhole Sensors in Long Horizontal and Multilateral Wells | OneSubsea
Tech Paper
Venezuela, South America, Onshore
Thomas F. Clancy and Jairo Balcacer, Petrozuata C.A.; Sebastian Scalabre, George Brown, and Paul O'Shaughnessy, Schlumberger; Ricardo Tirado, Baker Oil Tools; Greg Davie, Schlumberger
Paper Number
Presentation Date
29 September–2 October 2002
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Case History on the Use of Downhole Sensors in a Field Producing from Long Horizontal and Multilateral Wells


All of the production wells in this field were drilled and completed as horizontal and multi-lateral wells. The well designs range from a single lateral in a single sand body to where the upper and lower horizontal laterals intersect several sand lenses. The oil, an extra-heavy (9 API), high viscosity oil, requires a completion using artificial lift due to the low reservoir pressure, which will not support a column of water.

The use of down-hole pressure and temperature sensors with Surface Read-Out (SRO) was an integral part of the original well completions on production wells to monitor the individual well and pump performance. Vertical monitoring wells, drilled and completed through the multiple sand lenses present, expanded the use of down-hole sensors as data was sought on the area extent and pressure drawdown in the various sands being produced.

Efforts to determine the contribution to flow and the pressure losses encountered in horizontal wells led to the use of multiple sensors installed at depths along the long horizontal lateral. A change to the drilling of complex multi-lateral wells resulted in the use of tandem sensors to determine the relative contribution to flow from the lower and the upper lateral(s). All of these approaches, combined with the inability to use conventional Production Logging Tool techniques, led to the application of new technology combining fibre optics with multiple sensors to obtain a real time alternative to a PLT. As many as 15 surface read-out sensors were successfully installed in 7000 feet long horizontal well sections with measured depths up to 10,000 feet.

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