Improving Cementing Success with Better QC: Field Case Studies of using a World-First Quantifiable Mix-Water Analysis Technique

Mahavadi, Sharath Chandra (Schlumberger Doll Research Center) | Curtis, Nathan (Schlumberger Doll Research Center) | Taoutaou, Salim (Schlumberger)


Abstract Cementing is one of the most important steps in preparing a well for production. Critical parameters influencing the success of a cementing job are the concentration and the types of additives present in a mix fluid to prepare the cement slurry. However, it is extremely challenging to analyze water-soluble organics under oilfield operational conditions. In addition, with the complexity in chemistry of additives and mix fluids, it is also an analytical challenge to experimentally determine the quality of mix fluid and the slurry with standard analytical techniques such as high-pressure liquid chromatography (HPLC) or inductively coupled plasma spectroscopy (ICP). In addition to the general business need to verify chemical addition accuracy, in the field, the current practice to prepare mix fluid entails the addition of different additives either manually or using specialized liquid additive systems (LAS). Any human error in programming the LAS or manually adding the products yielding poor or no traceability for QA/QC could fail the cement job. This warrants the need for a reliable and field-robust method of quantifying additive concentrations in the mix fluid. To address this challenge, we developed a workflow using electrophoresis to address this issue to support operations. Electrophoresis uses an electric field to separate and quantify the components of a single fluid or a mix-fluid additive system. More importantly, we can simultaneously detect and quantify multiple chemistries in a single run. We have developed methods to analyze and quantify all the ingredients in an aqueous fluid system. This includes organics such as surfactants, natural and synthetic polymers, organic acid, and the inorganic ions that are common in seawater and most base fluids in the additive system. In the first step, we developed a method to analyze a single additive. This method addressed the issue of analyzing organics in aqueous fluid and demonstrated the applicability of this technology in determining the quality of the additives in terms of contamination. In later steps, the method was expanded to analyze and quantify dispersants, multicomponent retarders, and antifoaming agents individually as well together in a single run. Our study clearly demonstrated the electrophoresis technique can quantitatively differentiate multiple additives in a mix-fluid system while simultaneously estimating their respective ratios in the system. The developed method was applied to a mix-fluid system to identify a missing additive that led to the failure of a critical job. Overall, a simple and reliable technique is introduced to determine the quality and composition of additives and the mix-fluid system composition to enhance the reliability of existing processes and thereby improve the success rate of cementing jobs. Examples from the field will be presented.

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