F41 Block is located in the southwest of ShengLi Oilfield, DongYing, East China. The field has been operated for over 20 years. Water flood started in late 1990s using water from nearby aquifers and produced water. The reservoir is characterized with multi-thin oil layers of low permeability and high clay content, and saturated with medium light oil at temperatures of 110-120 °C. Carbonate scales were discovered since 2002, which formed in perforation holes, casing surface, tubing and surface facilities, having a great impact on well production. Frequent downhole scale clean-ups using acids and solvents have been carried in the past in an interval of around 3-6 months.
To control the scale problem and improve oil well production, scale inhibitor squeeze treatment has been tested to replace acidizing since 2006. A combined acidizing and inhibitor squeeze treatment has also been tried in the field for oil wells treated by the squeeze technique in the first time, in order to improve the treatment efficiency and reduce workover time. Experimental study has been conducted for selection of scale inhibitors in terms of chemical compatibility, efficiency of scale control, and adsorption characteristics of the scale inhibitors designed for squeeze treatment. The squeeze treatments have been performed in 6 oil wells, and good performances on inhibiting scale, increasing oil production, and improving pump efficiency have been observed. The squeeze life is expected to be more than two years. This paper reports the results of the experimental study and field operations. This was the first time of applying inhibitor squeeze technique to replace the traditional acidizing to deal with carbonate scales in ShengLi Oilfield. Its success and wide application will have a big implication on safe field operation and local environment protection (by reducing waste acid disposal) in the region.