Novel in-Field Technique to Monitor and Optimize Asphaltene Remediation and Inhibition Job with Direct Field-to-Laboratory Correlation

Abstract

Asphaltene precipitation and deposition is a major flow assurance issue faced by the oil and gas industry. The complex nature and non-uniform molecular structure of asphaltenes complicates efforts to accurately assess their stability. Moreover, developing test methodologies with strong laboratory-to-field correlation presents additional challenges. The focus of this study is to discuss the successful validation and application of a novel test method for determination and monitoring of asphaltene stability in a Gulf of Mexico deepwater field. Remediation and stimulation procedures were performed on a deep-water field in the Gulf of Mexico experiencing severe asphaltene deposition problems in the wellbore and near-wellbore region. This study evaluates the correlation between the thermo-electric properties as determined by Asphaltene Differential Aggregation Probe Testing (ADAPT) and dispersion tendencies of asphaltenes in treated and untreated crude oil samples at both laboratory and field environments. The remediation job was conducted through a multi-step process involving a coiled tubing clean out, solvent-soak, and continuous AI injection through downhole chemical injection tubing following the stimulation. Samples were collected prior to the start of treatment, during the initial flow-back of stimulation fluids, and over the course of one year following the stimulation. Field ADAPT measurements were performed to monitor the effect of continuous Asphaltene Inhibitor (AI) injection over time and validate the direct laboratory-to-field relationship. Higher ADAPT readings are indicative of a better dispersion state of the polar asphaltene fraction within the test sample. Hence, the pre-treatment samples were observed to have lower ADAPT values as compared to the flow-back samples collected after the solvent-soak stage. Stabilized higher readings were recorded for the samples analyzed in the next three months and a step-down trend was observed with reduction in AI dosage. Additionally, the amount of asphaltenes that precipitated from the field samples were also measured and followed an inverse relationship with the ADAPT values, corroborating the expected asphaltene stability behavior. Furthermore, differential pressure across the flowline was also monitored for this well to confirm the absence of asphaltene deposition throughout the assessment period. A strong correlation between the laboratory and field results obtained from this thermo-electric technique and its validation with other industry standard methods highlight the reliability and high degree of accuracy of the novel ADAPT method. With this study, an innovative method of assessing and monitoring the stability of asphaltenes and efficiency of an AI within the native crude oil medium is presented. The effectiveness of the technique to decipher and record variations during different stages of an asphaltene remediation job demonstrates its robustness and applicability as an efficient monitoring tool with great laboratory-to-field correlation.