ASP(alkali surfactant polymer) flood was initiated on March 15, 1997 in N-1DX block in Daqing oilfield; its main slug was completed on June 12, 1999. By September 23, 1998 pump malfunction occurred with a scale thickness of 1cm over in well bore. By the end of 1999, a serious scale was found in surface gathering and delivery system, with a 0.3cm of scale thickness found in single well pipes, gathering pipes as well as in heating furnace, this unfavorably affected current production.
In terms of this problem, we performed study of scale removal and inhibition.
Analytical study over scale content, scale forming mechanism and regularity.
Chemical agent study of scale inhibition.
Study of physical scale prevention method, and we performed comparison test on different well respectively, using coated nickel, three layered compound coated pipes and ordinary pipes.
We used hydro-electrical scale preventing unit, magnetic scale preventing unit in oil gathering pipes.
Through tests of the above methods in different wells, we obtained a satisfactory effect, the chemical agent method prolonged the pump check period from 30 days to 109 days; the coated pipe scaled slightly or didn't scale, and the scale was physically loosen. With these methods combined, scale prevention performed a good effect in well bores, single well pipes, oil gathering pipes and heaters. It ensured a conventional production in tested area. This paper presents the study of scale forming methods, the process of scale inhibition and the ideal effect we obtained.