Pumping Heavy Oils With The Aid Of Downhole Oil-In-Water Emulsifications

Abstract

Abstract Pumping high viscosity heavy oils is a difficult task under normal primary production operations. When the viscosity of the oil is increased beyond primary levels through the operation of a fireflood process, the problem is amplified significantly. Noreen began a major effort toward improving production levels from high viscosity wells at the Bodo Fireflood in mid-1984. Numerous pumping systems were tested during 1985 with limited success. A joint program with the Saskatchewan Research Council (SRC) to investigate the feasibility of injecting an adequate surfactant solution to form a downhole oil-in-water emulsion was initiated in late 1985. It was believed that improved pumping capabilities would be seen if emulsification took place, as water would be the continuous phase leading to much lower viscosities. Using their previous work in pipelining heavy oils as a base, SRC identified a surfactant which would produce a suitable oil-in-water emulsion. A single well field test was conducted in early 1986 using a hollow rod injection system. Results were encouraging as production increased significantly, rod fall problems decreased and pumping efficiencies improved. Subsequent installations in other wells showed similar results. Introduction The Bodo Fireflood Project is located in east-central Alberta about 125 km south of Lloydminster. It is operated by Norcen Energy Resources Limited on behalf of its joint venture partners, Canadian Occidental Ltd., Murphy Oil Company Ltd., and Texaco Canada Resources Ltd. The pilot was expanded from a single 9-spot pattern to a 7-spot configuration in mid-1982 following encouraging production performance. The original 9-spot pilot results have been described in a previous paper(1). Similar to many fireflood projects, numerous production problems were seen in the expanded Bodo pilot. Frequent sand clean-outs, poor pump efficiencies due to flue gas production, and serious emulsion problems have allIed to lower than anticipated production levels in the expanded project. In this paper, Noreen's most successful effort in improving production from those wells which experience emulsion problems will be detailed. In early 1983, a year after air injection was initiated in the new pattern injectors, viscous water-in-oil emulsions were seen at numerous producing wells. The observed emulsions ranged up to 50 000 mPa.s at reservoir temperature representing a tenfold increase over primary viscosities. These increased viscosities impaired production significantly. In some cases the problem was so severe that rod hang-up was still observed at pumping speeds of less than one stroke per minute (spm). With high fluid levels present at all the wells suffering from the high emulsion viscosities, a concentrated effort toward improving production was needed to enable the fireflood project to meet the projected production levels. Subsequently, experimentation with a number of different pumping systems was begun in November 1984. Initial attempts at improving performance at the high-viscosity wells included the installation of blend oil and produced water downhole injection systems using two different bottom-hole pump designs. No production improvement was seen with the water injection systems, and, subsequently, these wells were converted to blend injection following several months of evaluation.