Challenges in Scale Inhibitor Treatments in Multilateral Complex Wells - A Production Engineering Perspective with Case Study

Abstract

Abstract Water formed oil field scales impairs fluid flow and can lead to plugging of tubing, valves and surface equipment. When these scales affect well productivity or the integrity of facilities, it is necessary to remove these scales and/or adopt effective scale mitigation strategies. Calcium carbonate (CaCO3) is the most predominant scale in Saudi Aramco crude producers. Conventional bullheading treatments of phosphonate based scale inhibitor into vertical, deviated and horizontal producers are highly effective. In spite of the success of the scale inhibitor treatment in vertical and conventional horizontal wells, addressing the placement of chemicals in long horizontal and complex producers such as multilateral, maximum reservoir contact (MRC) and extreme reservoir contact (ERC) wells are always challenging and cost intensive. As completions become more complex, the challenges of providing full scale inhibition coverage in multilateral wells also become more complex. Limited accessibility, crossflow, rheology, and high permeability contrasts, all serve to make placement of the inhibitor a critically important component of any squeeze design. This paper describes some of the key uncertainties related to multilateral wells and possible treatment alternatives for proper placement of scale inhibitor into target segment or laterals. This paper also discusses a technical milestone achieved in successful treatment of smart multilateral (SML) wells for the first time in Saudi Aramco scale inhibitor treatment history that paves the way for treatment of such wells in the future. Lessons learned and experience gained to optimize similar future jobs are also described in the paper.