Reservoir paraffin precipitation: The oil recovery challenge in Dom Joao Field?

Dam Joao Field, located at Reconcavo Basin in northeastern Brazil, has been under production for more than 50 years. From the very beginning in 1947, exploitation has been plagued with problems that standard geology and reser voir engineering practices were not able to cope with. With an OOIP of 113 MMm(3) of 38 degrees API paraffinic crude, the current recovery factor stan ds at only 15%, in spits of the early implementation of waterflooding. Thre e major reservoir studies by different organizations. Petrobras included, w ere conducted over the years with significant impact on the geological mode l and appraisal of the original volumes. together with recommendations as t o the variation in the injection and production patterns. They were impleme nted accordingly but with limited success and, other than the heterogeneity of the reservoirs in the main Sergi Formation, no suitable explanation was found for the poor recovery performance, not to mention a solution to the problem. The size of the target oil and the constant threat of field abando nment, led to the approval of a research project in late 1993 as part of th e portfolio of PRAVAP, Petrobras Strategic Advanced Oil Recovery Program. I ts goal was twofold: verify the assumption of paraffin precipitation in the reservoir as the cause of the low recovery factor, and eventually put to t he test recovery strategies that Mould ensure the economical exploitation o f the shallow deposits of paraffinic crude in Reconcavo Basin. This paper s ummarizes the major accomplishments of this project throughout the 3 1/2 ye ars of research and development and the corresponding IOR field implementat ions.