Reducing Crystalline Silica in Oilwell Cementing Operations

摘要

Reformulating additives to reduce their crystalline silica content and modifying operational techniques are effective means for lowering worker exposure levels while maintaining additive performance.This is an important consideration as materials and methods used in operations are developed to reduce occupational hazards and maintain exposure to crystalline silica below permissible levels.A large opportunity to reduce crystalline silica dust in cement spacer additives exists based on annual consumption and mass fraction of crystalline silica in the additive.Described herein is an approach to identify candidate additives for a cement spacer system that aligns with crystalline silica reduction efforts.Focus is placed on the evaluation of low crystalline silica spacer designs for efficacy in well cementing and successful application in field operations.The additive components considered for use in reformulated cement spacer systems are analyzed using X-ray diffraction to quantify mineralogy.After identifying low-crystalline silica components,an investigation of the rheology,wettability,and compatibility of the reformulated cement spacer is carried out over the application space by employing a full factorial and space-filling design of experiment techniques.The reformulated cement spacer exhibits over 90% reduction in crystalline silica dust without sacrifice of rheological properties or material cost increase.The new low crystalline silica cement spacer(LCSS)has been validated in North American land operations.Bond logs confirm equivalent or better mud removal compared to previous cement spacers,with improved fluid interfaces and mud recovery.More than 2000 jobs have been performed with the new LCSS since introduction in January 2019 which corresponds to over 1.2 million pounds of crystalline silica dust eliminated from cementing operations.