Enhanced Approach for Asphaltene Risks Study to Unlock Hundred Millions Barrels Stranded Oil

Abstract

Severe Asphaltene deposition is encountered in some wells drilled in newly developed reservoirs of one of Abu Dhabi's giant offshore assets (Field AD), and for the first time, full well plugging with Asphaltene is experienced in the field. While successful curative clean up treatments are regularly made, the relatively high intervention frequency (once every month per well) has impeded the full-scale development of these reservoirs. This study shows how understanding the mechanism of Asphaltene stability/instability in field conditions can unlock the production of under-developed reservoirs (with hundred millions barrels of OIP) by anticipating and considering preventive measures during the design of new wells to limit Asphaltene deposition. In order to prevent the occurrence of Asphaltene deposition from reservoir formation to surface level, a Flow Assurance study was launched by the operating company with close support from the international partner. The objective was to determine the Asphaltene Deposition Phase Envelope (ADE) of the reservoir fluid by measuring onset pressures with Visual (High Pressure ‘HP’ Microscope) and Near Infrared Solid Detection System (SDS) as a function of 2 main variables: Different temperatures to investigate Asphaltene risks over the oil production pathway (at reservoir formation, and from wellbore to surface facilities) & Different Gas compositions to investigate the effect of rich Gas-Cap gas and injected lean gas on the Asphaltene stability. Also, the segregation of the nature of Asphaltenes within the reservoir has been investigated by using the experimental approach named ‘ASCI (Asphaltene Solubility Class Index) experiment’ introduced by the international partner (SPE-164184) to rank Asphaltenes’ solubility with atmospheric dead oil samples taken in different locations. In addition to that, 2 more experiments were performed: Organic – Inorganic test on solid sample to determine the composition and the nature of the solid deposit (whether it is Asphaltene or other type of depositions) & SARA analysis on atmospheric samples. This paper presents the improved work-flow based on the collaboration of the local operator and the international partner, introduces the use of ASCI (Asphaltene Solubility Class Index) experiment and discusses the results of the study and its way-forward.