This paper describes the progress and experience gained in North Gujarat oi1 field, caustic flood pi lot project. Laboratory investigations on acid number and interfacial reduction studies, to firm up the optimum concentration of caustic solution, encouraged the investigators to undertake further flood studies on actual cores and long core packs, SEM Micrograph studies were also conducted to evaluate the effectivity, reactivity and absorptions characteristics. Based on these investigations an inverted 5 spot pattern on a 10 acre pilot area was choosen. A 0.1 PV preflush of Sodium carbonate solution was injected in Dec. 1987. This was followed in July 1988 by 0.2 PV of 0.25% caustic solution followed by chase water injection started in March 1989 and still continues.

At the time of writing this paper in March 1989, 23% additional oil has already been produced from the pilot area. The pilot is sti11 producing oil, with 40 to 45% water cut and some emulsion. The final recovery is expected to be around 38%. This incidently matches well with the laboratory results. The pi lot performance so far had been satisfactory. No scaling was observed in the production string. Slight increase in injection pressure of about 20 kg/cm2 was observed. This increase, however, was shortlived. This further confirmed the laboratory investigations that emulsification, as a result of decrease in interfacial tension, and subsequent demulsification to release the caustic once again, seems to be the predominently dominant mechanism responsible for enhanced recovery of oil.

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