This paper will present a laboratory experimental work to examine the performance of a plurality of a solvent systems to dissolve wellbore organic deposits. Wellbore organic deposition has adverse effects on a petroleum well production or injection capability. The case study of the paper is a water injector, completed near a tar mat formation to provide pressure maintenance. The injector was identified with a wellbore obstruction. Samples from the obstructing material were analyzed in the laboratory using solvent extraction and infared spectroscopy. The downhole sample was found to be comprising 25 wt. % asphaltene and 75 wt. % maltene. The maltene was present in the form of saturates representing 32 wt. % of the sample and aromatics and resins representing 43 wt. % of the sample.
The wellbore sample was subjected to a range of solubility tests at a selected downhole temperature. The tests were conducted at static conditions; without agitation. Several solvent systems were evaluated as follows:
Xylene in diesel was used with 5 vol % mutual solvent. This system was examined at different xylene concentrations ranging from 10 to 30 vol %.
A solvent system containing n-methylpyrrolidone, diesel, surfactant, and an aromatic solvent.
A solvent system containing a chemical solvent, mutual solvent and diesel. This system was examined at different chemical solvent concentrations ranging from 10 to 30 vol %.
An emulsified solvent system comprising n-methylpyrrolidone, fresh water, emulsifier, and an aromatic solvent
All solubility tests were monitored as a function of the soaking time required to dissolve the organic deposits.
The results of this lab work showed that several solvent systems are able to dissolve the wellbore organic deposits at varying solubility performances. Factors such as chemical handling and cost were considered to select the proper solvent treatment system for field application.