In Situ Remediation of Heavy Organic Deposits Using Aromatic Solvents
Authors: Pacheco-Sanchez Juan H. , Mansoori G. Ali 
Published: December 2007

One of the effective and routine methods of remediation of heavy organic deposits has been the use of aromatic solvents which can dissolve the asphaltene content of the deposits and can cause the solid particles to he released from the precipitated mass. Remediation of the heavy organic deposits in the course of petroleum production has been a costly process and it has hampered the production activities in many parts of the world. In this report the authors review the in situ remediation of heavy organics including asphaltene resin, paraffin / wax, etc. in oil production and transportation practices and its relation with the laboratory and theoretical simulation experiments. Asphaltene is one of the major compound responsible for various arterial blockage cases in the petroleum industry. It is demonstrated that the asphaltene interaction with other heavy organics is a major factor for arterial blockage whether depositions will occur or not. Various mechanisms of asphaltene flocculation and micelle formation are reviewed and illustrative pathways are presented for each mechanism. The current in situ remediation and laboratory simulation practices in the oil industry to combat the problem is reviewed and analysis are made of the cause and effect of each factor influencing them. It is demonstrated that with the development of predictive modelling of heavy organic deposition one can make alterations in the production and transportation schemes to reduce and eliminate the deposition problem. With the development of predictive models one can also screen the candidate dispersants and solvents from the points of view of availability at the site, effectiveness and economy.

Introduction

Arterial blockage in the petroleum industry is mostly due to the deposition of heavy organics from petroleum fluids. Heavy organics such as paraffin / wax, resin, asphaltene diamondoid, mercaptdans, and organometallic compounds may exist in crude oil in various quantities and forms. Such compounds could precipitate out of the crude oil solution due to various forces causing blockage in the oil reservoir. in the well. in the pipelines and in the oil production and processing facilities. Solid particles suspended in the crude oil may stick to the walls of the conduits and reservoirs. The toughness of the precipitate has a lot to do whether there is asphaltene present in the crude oil even in minute quantities. Asphaltene which is a highly polar compound. could act as glue and mortar in hardening the deposits and, as a result. causing barrier to the flow of oil.

Heavy organics deposition during oil production and processing is a very serious problem in many areas throughout the world. In the Prinos field in North Aegean Sea. there were wells that, especially at the start of production, would completely cease flowing in a matter of a few days after an initial production rate of up to 3,000 BPD. The economic implications of this problem were tremendous considering the fact that a problem well workover cost could get as high as a quarter of a million dollars. In Venezuela the formation of heavy organics (asphaltic sludges) after shutting in a well temporarily and/or after stimulation treatment by acid has resulted in partial or complete plugging of the well. At the Hassi Messaoud field, Algeria. deposit of heavy organics in the tubing has been a very serious production problem.

Heavy organics have played a significant role in the production history and economics of the deep horizons of the Ventura Avenue field, California. Heavy organics deposition problems in this field ranged from deposition during early oil production and deposition resulting from well acidizing and CO2 injection during enhanced oil recovery (BOR).