From Lab to Field: An Integrated Approach to Successfully Restore The Productivity of Damaged Wells with Organic Deposition

Abstract

Abstract Asphaltene deposition is a major formation damage issue in production wells with asphaltene problematic oil. Asphaltene can precipitate within the reservoir or in production tubing, resulting in partial or total loss of well productivity. This is especially a large concern in reservoirs with high gas-oil ratio (GOR), as more gas can dissolve in the oil and strip out the asphaltene. This anticipated asphaltene precipitation mechanism might be responsible for several partially or totally damaged wells in Field-A with asphaltene precipitation. An extensive laboratory study including solubility tests, saturate aromatic resin asphaltene (SARA) analysis, compatibility tests and coreflood experiments was performed in this study. Solubility tests were conducted at reservoir temperature (220 °F) and elevated pressures using asphaltene obtained from a bailer sample to determine the effectiveness of different solvent systems. SARA analysis was performed to assess the stability of the reservoir oil of interest. Compatibility tests and coreflood experiments at reservoir conditions were also conducted to assure solvent system compatibility with formation fluids. In addition, other factors including the overall cost and environmental impact were taken into account in choosing the most suitable solvent system. Initial lab testing presented a number of candidate solvent systems with high asphaltene solvency power. Some solvent systems were ruled out because they were damaging to core permeability as indicated from the compatibility tests and coreflood experiments. A case study of two successful chemical treatments performed on Well-A with a time interval of more than two years is presented in the paper. The first treatment was successful in restoring productivity of Well-A while the second one was able to remove the partial organic deposition damage with a cost saving of 60%. Using the selected solvent system, a two-stage remediation procedure was implemented to dissolve the organic deposition in the horizontal open-hole section of this well. The first stage included bullheading the solvent, allowing it to soak for 24 hours to clean out the tubing. The second stage involved injecting the solvent in the open-hole section using coiled tubing (CT) with jetting/pulsing mechanism. Results showed an increase in the wellhead pressure by 40% and consequently well productivity, indicating the successful dissolving of the organic deposition. This paper presents a new methodology in incorporating all the mentioned analytical techniques into choosing the most proper and cost effective asphaltene treatment solution for a specific reservoir to have a successful field treatment.