A New Downhole Heating Technology Study and Pilot to Improve Steam Quality

Abstrct This article introduces an unconventional downhole heating technology to improve steam quality. We put a long heater installed in coiled tubing consuming electric energy to the well to heat the steam injected from the wellhead to reservoir to increase the steam quality whose depth up to 1600m or larger, so the reservoir need high quality steam can be developed. The most important part of this technology is the downhole heater. Big power is the first character and it must be easy to operate, so it is difficult to produce. After many times failures, the heater is ultimately produced successfully by pre-installing special electric wire in coiled tube with insulation around them and then drawing the coiled tube in special machine. We call it "monolithic-draw" technology. With this technology, the produced heater can produce enough energy to improve steam quality downhole and it works safely. Matched pull-push equipment and intelligent power adjust module are also developed. The heater is produced first time and its length is about 200 meters and the power is about 400kW. The diameter is about 33mm and we test the insulation ability and heating speed in lab. After complicated designed test, we get the relationship between steam quality, power and injection speed, so we can adjust it to adequate power to satisfy field need. Field pilot shows it can heat about 20000m3/h air injected into the well to 480°C and heat low quality steam with 50% dryness to higher quality steam at the depth up to1600m- 2500m. At the depth, now with this technology we can get 50% dryness steam at well bottom by injecting steam from wellhead, so many previous undeveloped super heavy reservoirs can be developed economically. Field pilot was conducted in well group 68, the well group production is increased from 33t/d to 69t/d because of the improvement of steam quality and the operation cost is reduced by 41% because there is no heat loss. This technology is new developed and it benefits to reduce carbon dioxide discharge because the heater can use green electricity made by wind or sun. It will be widely used in deep buried heavy oil reservoir, and it may be a revolutionary steam producer in comparison with conventional steam producer.