Impact of Asphaltenes Deposition on Completion Design for CO2 Pilot in an Onshore Abu Dhabi Field

Abstract

Abstract Gas injection is one of the most common methodologies for Enhanced Oil Recovery (EOR) in the oil and gas industry. One of the challenges associated with gas injection, e.g. natural gas, CO2 and N2, is potential asphaltenes precipitation and subsequent deposition causing blockage throughout the production system. It is crucial that precipitation of asphaltenes is identified early in the planning stage of any EOR project so that mitigation strategies are put in place to avoid negative impact on well performance. A line-drive pattern CO2 pilot is planned in a super giant field A onshore Abu Dhabi and hence single phase bottomhole samples were collected from a nearby well to evaluate asphaltene stability under CO2 gas injection. This paper presents the results of the lab work that clearly indicate no asphaltene deposition problems during natural production; however, asphaltenes will precipitate when CO2 is mixed with the crude at mole fractions as low as 0.2. Based on the experimental results and on field results from another CO2 pilot in field B, which experienced asphaltene deposition problems, it was deemed necessary to include provisions for continuous downhole chemical injection of asphaltene inhibitors in the CO2 pilot producers for field A. The challenge is to combine the requirements to prevent CO2 corrosion and to prevent asphaltene deposition in the well. The paper describes the different completion design options that can be used to achieve the desired target taking into account the cost impact. The designs incorporate combinations of different tubing materials and chemical injection options with pros and cons to using each, keeping in mind the reservoir monitoring requirements that can add more constraints to the completion design.