Abstract
The common practice of using chemicals and solid-entrained liquids to remove soft scales in production tubings is associated with a high risk of contaminating the environment and eroding pipe internal surfaces. Due to the suspended solids, the current practices are also characterized by high pumping costs and are more problematic to rotating parts of machinery than freshwater. As a cheap and less risky alternative to these corrosive chemicals and liquids, this paper investigates the feasibility of utilizing multiple high-pressure (HP) water jets for the same objective. A total of 54 experimental trials were conducted to study the effects of four factors on the efficiency of scale removal with multiple flat-fan nozzles at an orientation of 25°. The factors investigated are (1) number of nozzles; (2) spray injection pressure; (3) stand-off distance between the spray nozzle and target scale; and (4) condition of the production tubing: ambient and pressurized. Details of the experimental set-up, equipment and procedure are provided. The results of these controlled experiments show a positive correlation between descaling efficiency and spray injection pressure. The same set of experiments reveals a negative correlation between descaling efficiency and nozzle count, as well as between descaling efficiency and spray stand-off. However, for the scale samples and range of parameters investigated in this study, descaling efficiency did not exhibit significant dependency on the chamber conditions, i.e. ambient versus pressurized. The results of this study provide some insights into the feasibility of multiple HP water jets as a cleaner alternative to the use of corrosive chemicals and solid-entrained liquids to remove soft scales in production tubings in oil fields and other applications.
Highlights
The production and transportation of petroleum from subsurface reservoirs to end-users are accomplished with circular pipes, which include production tubings, pipelines similar process vessels (Mansoori et al 2017; Nejad and Karimi 2017)
To ensure that the fabricated scale samples were representative of typical oil field paraffin scales, a cooling curve matching test was performed on the molten waxes
The impacts of four key factors were investigated vis-à-vis (1) number of nozzles; (2) spray injection pressure; (3) standoff distance between the spray nozzle and target scale; and (4) condition of the production tubing, both ambient and pressurized. The results of these experiments showed that the use of high-pressure water jets as a cleaner method of descaling is technically feasible
Summary
The production and transportation of petroleum from subsurface reservoirs to end-users are accomplished with circular pipes, which include production tubings, pipelines similar process vessels (Mansoori et al 2017; Nejad and Karimi 2017) It is not unusual for these conduits and conveyance systems to suffer flow restrictions resulting from solids depositions, as well as corrosion failures due to internal abrasion by suspended solid particles (Peng and Guo 2017). Recognizing the limitations of chemical dissolvers, the use of relatively fresh water has been considered as an alternative In principle, this alternative technique entails spraying HP water jets at deposits on targeted surfaces. This alternative technique entails spraying HP water jets at deposits on targeted surfaces Among other attractions, this relatively new technique promises improvements in ease of operations, scale removal efficiency, HSE performance, while still reducing costs. The results obtained present a useful basis for quick decision-making in relation to the design, implementation and optimization of HP water jets for remediating scale problems in an oil field
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