Abstract
This study established the detailed root cause of complex layered scale deposition along the completion jewellery and production tubing, qualitative and quantitative scale composition, special design of the scale treatment and future mitigation plan to handle the scale/asphaltene issues in ADNOC Onshore gas wells. Gas producers are having scale problems due to corrosion products with mixture of organic material deposition which may be from produced gas and condensation of heavier hydrocarbon due to change in pressure temperature profile along the tubing. Gas injectors are having scale/asphaltene deposition indicating the lubricant components thus suggesting an exogenous source of scaling (i.e. external sources such as oilfield tools, seals, valves, upstream equipment).
Two stage chemical scale treatment designed after conducting extensive lab test to reach the 75 – 80 % solubility cost effectively. Mechanical treatment with sterling beads evaluated for hard scale by considering the tubing integrity. Scale treatment operation executed with coil tubing at 3 wells and successfully achieved the desired results.
Identified the root causes of scale build up and chalked out future mitigation plan to maintain the well integrity, flow assurance and cost optimization. In short term, scale issues can be handle by evaluating the suitable chemical with reference to well type, improving chemical injection system to minimize the corrosion products and improving the quality of injected gas for gas injection system. In the long term, scale formation can be avoided by squeeze inhibition treatment (scale/corrosion), mechanical treatment of scale removal for hard scale and improving in downhole completion jewellery maintenance.