Quality Assurance and Quality Control of Surfactants for Field-Scale Enhanced-Oil-Recovery Pilot Projects

Abstract

Summary Alkaline/surfactant/polymer (ASP) flooding is an enhanced-oil-recovery (EOR) technique that involves the injection of a solution of surfactant, alkali, and polymer into an oil reservoir to mobilize and produce the remaining oil. There are several pattern-flood pilots in progress or that will soon be executed to evaluate ASP at a scale relevant to commercial-scale application. The quantities of surfactants needed for these pilots and potential future commercial-scale applications are large (hundreds to thousands of tonnes) and necessitate large-scale manufacture using existing processes and plants for the different manufacturing steps. These operate under slightly different process conditions than those used to make the smaller quantity (50 to 400 kg) of the reference blend used to design the formulation in the laboratory. The upscaling of the surfactant production itself is an essential step to enable field-scale implementation of ASP. To ensure and control the quality of the surfactants produced for pilots with Shell interests, a stage-gated quality assurance/quality control (QA/QC) program was designed and executed. The application of the QA/QC process for a high- and a low-active-matter surfactant-blend concentrate (approximately 60% and 20% active, respectively) is used to illustrate the process. The early definition of the QA/QC program provided a framework with clearly defined stages for upscaling from laboratory- to large-scale production. The definition of analytical and performance-based laboratory experiments with upfront-defined specifications (minimum and maximum values) and repeatability allowed for clear, unambiguous decisions. Correlations between composition and performance that were developed dependent on pilot-scale production were essential to assure the performance of the larger-scale production. Corefloods, used as the ultimate performance check, showed virtually identical performance for pilot-scale prepared surfactants and surfactants from different large-scale batches. The paper illustrates that consistent industrial-scale production of surfactants for application in chemical EOR (CEOR) is feasible. To ensure the quality of such surfactant requires a detailed QA/QC program. The successful execution of the QA/QC program for the surfactants for the pattern pilots ensures that the produced large-scale surfactant blend performs as the reference blend used to design the formulation.