Treatment of Alkaline Surfactant Polymer Flood Produced Chemicals in a Custom Built Flowloop Separation Facility in the Sultanate of Oman

摘要

Alkali Surfactant Polymer (ASP) flooding was piloted in 2016 in a clastic field in Southern Oman. One of the main risks identified prior to the pilot is the impact of the produced ASP chemicals on the surface oil/water separation. To un-risk this issue, a custom-built fluid treatment facility (called flow-loop) was constructed to treat ASP produced fluids and determine its impact on the larger scale system. The flow-loop contains the typical technologies currently deployed in the field for processing produced crude (i.e. oil heaters and separators) with new technologies (bulk fluids heater, electrostatic desalter and new types of demulsifiers) in case existing production system is not adequate to produced fluid. Three groups of tests were conducted over a period of 12 months; the first part was the baseline tests where the performance of the system without any produced ASP chemicals is tested when operating as close as possible to the operating conditions of the existing field production station. Following the baseline test, more tests which were called optimized baseline tests were conducted to determine the impact of the technologies not deployed in the current production station in improving the oil and water separation. That included increasing the bulk heater temperature, oil heater temperature, increasing the incumbent demulsifier rate and applying the electrostatic heater current (crude viscosity is a few hundred at ambient temperature). The flow-loop was able to dehydrate crude quality of 1-2.5% BS&W and 100 ppm oil in water during the baseline test. The flow-loop was able to achieve 0.6% BS&W during optimized baseline tests. The second part was the online produced ASP slug chemicals impact test, which was the performance of the system when the chemicals reached the pilot producers, by operating with the baseline operating conditions and by attempting to improve the performance by operating the new fluid treatment technologies. The flow-loop could dehydrate the crude close to the baseline quality with the ASP chemicals naturally produced to surface (typical values measured are in the range of: pH= 9.3, Salinity = 6000 ppm, water viscosity= 15 cP at reservoir conditions, surfactant= 100 ppm), however more dehydration capacity is required with ASP being present. Significant water quality deterioration was seen with presence of ASP chemicals, but application of new demulsifier technologies could mitigate water quality to normal levels (comparable to conventional crude). The third part was like the second part but with additional surfactant injected directly to the surface producer aiming to increase the concentration of ASP slug to determine the impact of the higher surfactant concentrations (pH= 9.3, Water Viscosity= 10cP, surfactant= 400 ppm) on treatment facilities. The flow- loop was able to dehydrate oil but more separation capacity with appropriate demulsifier is required to achieve sellable oil specs. The water quality deteriorated significantly and this could also be mitigated to normal water qualities by appropriate demulsifier and optimized dosing.