A New Acid Treatment Procedure to Improve Injectivity in Brazil Offshore Horizontal Wells

摘要

Generally, offshore horizontal producer wells in Brazil do not require acid treatments after a gravel pack. The drill-in fluids' filter cakes have low lift-off pressures and are readily produced through the gravel and the screens. Injection wells, however, require acid treatments to break down the filter cake and establish low skin factors and favorable injection profiles. Improved HF Acid System has been used successfully after gravel packs or in other wells to remove drill-in fluid damage and improve injectivity in the formation. Good acid designs were achieved through knowledge and lab tests. Due to the difficulties of obtaining core plugs for lab testing, specialist simulation software has been used to determine the best acid composition. Operationally, the great challenge is reducing rig time for acid jobs without affecting treatment quality. Pumping acid through a longer screen interval using a Horizontal Single Trip (HST) system significantly reduces the treatment time. This paper describes a new procedure to design and pump acid jobs in Campos and Espirito Santo Basins, based on: application of specialist simulation software to design the acid system; inclusion of 15% HC1:corrosion Inhibitor blend ("Mud Cake Remover") before the classical acid treatment; and pumping the treatment through five screens joints using the HST system.