Water flooding is the hinge pin for Gemsa Oil Field. Water injection is supplied from shallow water supply wells. Compatibility tests had indicated probable deposition of calcium sulphate scale on surface and subsurface production equipment. Calcium sulphate scale has been recognized to be a major operational problem. The bad consequences of scale formation comprised the contribution to flow restriction thus resulting in oil and gas production decrease. The nature of calcium sulphate scale is very hard and can't be dissolved with known dissolver. Sister companies that has similar problem were always going to the mechanical remover options (1).
Extensive lab and field work was conducted to determine the suitable chemicals to dissolve calcium sulphate scale.
This paper describes the development and field application of chemical treatment to remove scale in an offshore 8" production line in Gemsa oil field. Continuous precipitation of calcium sulphate scale caused partial plugging of the pipeline. This partial plugging created a back pressure on production wells which decreased the productivity. The field production has been decreased to almost one tenth of the normal field production level.
A thorough investigation was conducted to identify the composition and location of the scale, in order to recommend a suitable chemical to remove the scale, and to assess the effectiveness of the treatment method in the field.
Based on extensive lab studies, Soda Ash was tested and applied in production line to remove the scale efficiently; the program was designed taking into consideration the nature of the scale.
The treatment program included three - staged process:
The use of an organic solvent
The main treatment (Soda Ash).
The post flush stage (15 wt% HCl),
The job results were outstanding, where as
Production increased by about 2,000 BOPD
Launcher pressure dropped by about 270 psi.
Decrease the back pressure on our producing wells.
Additional producing wells into production.
Efficient cost /Bbl.