Steam injection, one of commercial technologies widely used to develop heavy oil reservoir, has brought reservoir engineer's attention to improve performance of waterflooding, light oil reservoir and enhance its oil recovery. Sarto reservoir, located at the transitional belt in Daqing Oil Field, is the case of steam injection utilized. It is a typical multi-layer sandstone fluvial and deltaic deposit with depth of 1000~1200m, permeability of 500~2000md and porosity of 20~30%, surface oil viscosity of 50~100cp @ 50oC, wax content of 25~30% and freezing point of 30~35 oC.
The reservoir came into development in 1989 with line drive water injection with line space of 250~270m. Water injection has good response at the early stage and several years' later water cut increased rapidly. In 2005, water cut increased to 90%. However, oil recovery was only 14%, lots of oil has been left in the reservoir. Measurements such as water plugging, profile modification and layered water injection show good but unexcited response. In 2005, steam injection was utilized to improve the performance and enhance the oil recovery.
The paper will firstly discuss mechanisms, strategies as well as barriers and difficulties to high recovery of steam injection in such waterflooding, light oil Sarto reservoir. It will also detail reservoir engineering study, such as well pattern suitable to steam injection, development manner, injection and production system, and its pilot test plan. Finally, the paper will introduce production history of steam injection and analyze its performance and influence factors. The pilot shows us that steam injection has great potential in improving injection and production profiles, increasing productivity, decreasing water cutand enhancing oil recovery.
Steam injection, one of commercial technologies widely used to develop heavy oil reservoir, has brought reservoir engineers 'attention to improve performance of waterflooding, light oil reservoir and enhance its oil recovery. There are several successful pilot tests of steam injection in the waterflooding reservoir1 such as Wilmington oil field2 (1981), Breafield (1973)3, Elk Hill (1987)4, Ruhlermoor (1987)1, Minas (1997) 1.
Sarto reservoir, located at the 4th transitional belt in Daqing Oil Field, is developed by nearly20-year's waterflooding with 14% oil recovery but 90% water-cut. It is a typical multi-layer sandstone fluvial and deltaic deposit with depth of 1000~1200m, permeability of 500~2000md and porosity of 20~30%, surface oil viscosity of 50~100cp @ 50oC, wax content of 25~30% and freezing point of 30~35 oC. How to rejuvenate such mature reservoir with 'secondary water body' and water channel formed during long-time water flooding? The answer is steam injection. This paper will introduce lab experiments and numerical simulation to study the steam injection in the mature water flooding reservoir such as its mechanisms, its key influence factors and its strategies as well as the pilot test performance.