Improving the Steam Quality injected in a Heavy Oil Reservoir by Using a Cyclonic-Type Condensate Separator: A Field Pilot

Abstract

Steam quality surveillance is important for steam injection since the oil production response expected depends on the heat injected to the reservoir. This paper focuses on the evaluation of a mechanical device whose target is to increase the steam quality by means of physical principles such as centrifugal force and gravity, removing the water liquid phase not converted into steam as a result of the design limitations that a steam generator has in terms of steam dryness by scale deposition in the boiler piping. The following program was implemented to test the device, a cyclonic condensate separator, including different operational ways for disposing of the liquid phase removed by the separator. To begin, the separator was engaged to a steam generator outlet (25 MMBTU/hr capacity). A group of 3 wells close to the steam generator was selected to compare three operative ways for handling the hard and hot water removed by the cyclonic separator. An additional liquid phase sampling trap was installed downstream of the separator in the steam line to verify the steam quality by means of digital conductivity measurements. Steam injection on selected wells started sequentially and operational parameters as pressure, temperature, conductivity, steam quality, and gallons per minute (GPM) were collected from the steam generator and the cyclonic separator. Theoretical calculations for determining the heat generated, removed (via the liquid phase) and finally injected into the wells in MMBTU were done by using variables such as feeding water, operation time, enthalpy and steam quality, contrasting results obtained against the values given by the cyclonic separator. Finally, production results are shown and analyzed although they are not considered as relevant for evaluating the cyclonic separator effectiveness, since the main objective of the pilot was to check the steam quality increasing (above 95%) at field conditions. By using the cyclonic condensate separator, the injected steam quality increased from 81% to 98% on average during 41 operation days in a row. This improvement also was confirmed by the steam-trap installed downstream of the cyclonic separator (only 1.6% difference). The steam pressure and temperature losses caused by the cyclonic separator were 17% and 5% on average, respectively. From the cyclonic separator data and theoretical calculations, it was determined the cyclonic steam separator removed 227 bbl of water per day (17%) on average from the initial volumetric flow rate given by the generator (1407 water bbl/day at 41 GPM). In terms of energy, the cyclonic separator removed as liquid condensate 8% (41 MMBTU/day) of the initial energy given by the generator (527 MMBTU/day), in search of increasing the steam quality. From the three disposal options considered for the liquid phase that was removed, it was determined that injecting the liquid directly into the main production line was the most efficient way for handling this fluid, since it was observed that the hot water (354 °F and 21% flash steam) acted as a hot spot, improving the oil mobility inside the pipeline. This approach also reduces the costs of transporting the water removed to the treatment facility.