Exploration • Drilling • Field Services
such as the North Sea, California, Venezuela, Canada and Africa. As a result of our targeted research and
development, we have developed new demulsifier intermediates to be classified as ‘gold’ with no substitution warnings - the very best environmental category in the North Sea.
relationship between the BS&W and the volume of water the field produced and handled at the plant. Tis would suggest that the water handling limitations of the plant were being exceeded. Residence times would also decrease as the
produced water rate increased from 8,000 to 16,000 m3
/day. A slow increasing trend in the BS&W occurred
Fig. 2. Crude oil and water rates versus the export BS&W, arrow indicates change in demulsifier chemistry schematic.
Case history Tis case history tracks the continual improvement cycle for the fluid separation process from a heavy oil field over a period of three years. One of the major challenges posed by the operator of this 13 to 16° API crude oil was to discontinue the injection of two separate demulsifier formulations and begin injecting a single demulsifier product. Tis was not an easy task due to the very different conditions that existed at the two injection locations. Te first location was at a series of injection points upstream of the gathering stations out in the field, prior to separation, and the second was at the process plant. Te operator required a very strict 0.5 per cent BS&W on the crude exiting the plant for sales. A schematic of the battery plant has been given
in Fig. 1. Injection of two different demulsifier products in the field and at the plant occurred for several years (both were mixtures of EO/PO block polymers and alkoxylated amine based resin molecules) with relatively trouble-free operation - the export BS&W was in specification. However, in mid-2007 it was a requirement to not only move to single demulsifier products for application in the field and the battery, but also to decrease the BS&W to 0.2 per cent. Te reasons for these changes were to ease logistical and operational issues by moving to one product and the BS&W specification was to have more of a buffer for the sales specification. Fig. 2 shows the evolution of the export BS&W with total oil and water flow rates. Tere is a direct
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from early 2005 to the end of 2006 (A), and this could be explained by increasing water production rates and generally decreasing demulsifier injection rates. At the beginning of 2007, an increasing trend was experienced in the BS&W (B), and this was commensurate with a marked increase in the produced water rate. By June 2007, the new single demulsifier product was introduced and, even though further increases in produced water rates occurred, the increasing trend in BS&W was halted, where it has maintained an average of 0.4 per cent (C). While the change in demulsifier did not decrease the BS&W to the target of 0.2 per cent, the change was positive because it ensured faster water drop and more efficient separation at the plant, even with massive increases in gross fluid throughput, and resulted in maintaining a constant BS&W. Optimisation continues with the new product combination to reduce the injection rate to the most economical concentration.
Summary From field testing, sampling and the demulsifier optimisation exercise, the following conclusions can be made:
● By injecting two separate demulsifier products prior to mid-2007, operations were relatively trouble-free. A change to the BS&W requirement and a desire to move to a single demulsifier product applied in the field and at the process plant gave significant treatment challenges.
● Redesigning the bottle test procedure was required in order to more accurately mimic the field application of a single demulsifier product.
● Te general increase in export BS&W was most likely attributable to the large increase in water production.
● Te change in demulsifier chemistry was positive because it halted the increasing trend in BS&W commensurate with water rate increases. ●
Enter 36 or ✔ at
www.engineerlive.com/iog
Jonathan J Wylde is UK Business Manager, Clariant Oil Services, Dyce, Aberdeen, UK.
www.oil.clariant.com
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