New Innovative Technique for Scale Management During Water Flooding in Offshore Reservoirs

Abstract

Offshore reservoirs EOR present new challenges every day, during water flooding the primary injectant is sea water which is the mostly used fluid in Egyptian offshore wells in Mediterranean sea and Red sea which demonstrate undesirable problems to overall oil recovery process, main problem is scale deposits formation, specially of metal sulfate scale. Scale deposition was found in many offshore wells in injection tubes and production well and both surface and subsurface equipment causes production declines and costing millions of dollars every year In this study we developed unconventional techniques to remove and control scale formation during using sea water in injection, That techniques must be efficient and consider all reservoir and water compatibility aspects. When scales found in either in water flooding pipelines or oil production pipelines and surface equipment's, the conventional way to remove those scale and regain efficient flow is mechanical jet blasting using high-pressure water to crack the scale but it was a time consuming root and need special equipment and large man power although it wasn't that efficient in areas with heat exposure and it can't reach some areas. So we moved to next root for removing scales by chemical cleaning based on inorganic acid like hydrochloric acid, sulphuric acid, etc. although it can dissolve the scale in very limit efficiency we didn't accept this method because those chemicals was very corrosive to metal surface like cast iron and stainless steel grade 304/316 also using those chemical present hard handling problem for adding or dilution. Therefore, we had to take the challenge to develop our new chemical cleaning methodology that combines between efficiency and safety. In new methodology, we developed new chemical formula based on mild organic acid mixture combined with sequencing agent, anti-re-deposition agent, wetting agent and pickling agent to chemically dissolve the scale in efficient and safe way. The chemical cleaning technique was successful to dissolve the scale in very short time and in safe way to metal surface like cast iron and stainless steel. This invention is useful for the removal of sulphate scale like iron sulphate, calcium sulphate, barium sulphate and strontium sulphate from process equipment including pipes, pumps and storage tanks. It is also can be used to the removal of these scale deposits from other equipment such as boilers and heat exchangers.