Successful Asphaltene Cleanout Field Trial in on-shore Abu Dhabi Oil Fields

Abstract

Two of the prominent on-shore fields in Abu Dhabi are facing asphaltene deposition in a number of their oil producing wells. Several studies were carried out to understand the reasons for asphaltene unstability in the crude in both fields to help develop the appropriate mitigation strategies. A summary of the findings will be presented in this paper, however, the focus will be on the efforts undertaken to improve the current asphaltene clean-out formulations that are being used in the field. These formulations are composed of a dispersant chemical mixed with diesel as a solvent in 20:80 ratio and are pumped with the use of a Coil Tubing Unit (CTU) in tandem with jet blaster. However, the success rate reported for such clean-up jobs was 40% on average. Hence lab testing was carried out on a number of new dispersants and other potential solvents to improve the efficiency of the clean-up operations. After testing a combination of 8 commercially available dispersants with 3 solvents: Diesel, light gasoline oil (LGO), heavy aromatic naphtha (HAN), it was clear that a mixture of HAN with 3 particular dispersants in a 90:10 ratio were many times more efficient than the currently used formulations. These top lab ranked formulations were then field trialed in 7 wells by bullheading only, soaking overnight and running a gauge cutter to prove accessibility and success of the clean-up job. The wells were found to be perfectly cleaned with 25% reduction in the chemical requirement and a major saving in terms of avoiding the use of CTU for the clean-up operation. Implementation of new formulations would affect multimillion dollar cost saving. The savings increase many fold when opportunity costs against the previous unsuccessful jobs is taken into account. Besides, valuable resources like CTU can be gainfully deployed elsewhere. Results of this field trial will have larger implications for ADCO in the future as the number for asphaltene affected wells is rising as a result of field maturity and implementation of Enhanced Oil Recovery (EOR) and Artificial Lift (AL).

Asphaltene Stability in Crude Oil during Production Process

“…As an example, several major onshore fields in Abu Dhabi are challenged with asphaltene deposition in their producing wells. One asphaltene clean-up operation using organic solvents and coiled tubing unit costs US $200,000 [9]. In addition, during the existence of CO 2 pilot project three asphaltene removal jobs were conducted [10].…”

Perbandingan Metode Coiled Tubing Dan Pump Pada Aplikasi Solvent Treatment Berdasarkan Parameter Success Ratio Dan Cut Off Di Lapangan Fash

“…Dalam melakukan injeksi pelarut yang umum digunakan ada 2 cara yaitu dengan menggunakan coiled tubing dan pump. Menurut Misra et al, (2013) dalam jurnalnya disebutkan bahwa penggunaan pompa lebih efektif dalam menurunkan kadar asphaltene, dimana dari 7 sumur yang diinjeksi pelarut hanya 1 sumur yang diinjeksi menggunakan tabung melingkar. 1 sumur memiliki asphaltene yang ada pada banyak interval.…”

Evaluation of the Effectiveness of Inhibitors for Middle Eastern Asphaltenes by Quartz Crystal Microbalance with Dissipation

“…These methods are typically referred to as enhanced oil recovery (EOR) techniques, and the techniques that use gas or seawater are receiving increasing attention. , A key practical and economic concern during the application of these methods is the recurring problem of accumulation of organic scale in the form of deposits that are mainly composed of polycyclic aromatic hydrocarbons referred to as asphaltenes. As a result of the sudden change in the chemical environment upon extraction and/or EOR, asphaltenes that are normally solubilized in crude oil become unstable and precipitate, and this could result in deposition and clogging of the wells and production equipment. − This, in turn, could ultimately lead to a severe reduction in production economics because the affected wells have to be chemically or mechanically cleaned, resulting in production deferral or even shutdown of the production process in the case of highly affected wells. − Asphaltenes are an intractable mixture of chemical compounds composed of the high-boiling point fraction of petroleum crude oils. Although it is practically impossible to separate and chemically analyze individual asphaltene molecules, substantial progress has been made recently with the elucidation of their chemical nature. − Albeit they always vary drastically in composition depending upon the geological source, this oil fraction is known to be enriched in heteroatoms (typically nitrogen, sulfur, and oxygen) and has a comparatively high degree of aromaticity relative to other crude oil components as a result of the presence of a polycyclic aromatic core in their structures .…”