Published: 07/01/2018
Published: 07/01/2018
An operator is producing oil from one of the world’s deepest supergiant oil fields with an ultrahigh H2S content—up to 15% to 17% by mole. The reservoir is managed so precisely that the wells produce less than 1% water cut. However, the field treatment plant has a low tolerance for the water fraction of the production stream because of the excessive H2S content and to fulfill the operator’s commitment to environmentally responsible management of the cumulative produced water volume.
This challenging situation means that allocating and monitoring the wells that produce even a very small quantity of water is of significant importance for reliable and efficient processing at the oil treatment plant and planning future well locations. The operator wanted to replace discrete manual sampling and analysis with an automated inline approach that would provide continuous monitoring.
Schlumberger proposed using the AquaWatcher Surface water salinity sensor employing latest- generation microwave sensor technology for high-accuracy, high-resolution measurement of water conductivity in wet gas and water-continuous multiphase flow. The real-time output of water salinity is extensively qualified for the detection of water from 100 ppm at a gas volume fraction (GVF) > 95% and 200 ppm at GVF from 70% to 95%.
To validate applicability at the oilfield’s conditions, the AquaWatcher Surface sensor was installed on the blind T-connection of a Vx Spectra flowmeter in a mobile system employed for well test cleanup operations. This technology pairing provided numerous advantages:
Within 2 months, six wells were tested with the AquaWatcher Surface sensor. The sensor performed robustly within specification in comparison to reference water volume fraction (WVF) measurements from the previous manual sampling and analysis procedure.
The AquaWatcher Surface sensor detected water at levels as low as 50 ppm in the field’s challenging conditions of H2S concentration up to 15%, oil flow rate range at 1,400–14,500 bbl/d, gas flow rate range at 3–35 MMcf/d, and GVF range at 85%–94%.
In addition to receiving accurate, continuous, real-time data for managing production and planning, by replacing manual sampling and analysis with automated monitoring, the operator mitigated the potential exposure of personnel to H2S.
Challenge: Automate water detection for the critical production management of high-rate, multiphase producing wells with H2S content up to 15%–17% by mole.
Solution: Implement inline continuous water detection and salinity monitoring during flowback operations by integrating the AquaWatcher Surface water salinity sensor in existing installations of Vx Spectra surface multiphase flowmeters.
Results: Detected water at levels down to 50 ppm with automated inline measurement while reducing potential exposure to ultrahigh levels of H2S.
