Thermodynamic Modelling for Mapping Wax Deposition Envelope for an Identified Niger Delta Oilfield

Abstract

Abstract Wax deposition is a major concern for the pipeline and oil industry. During normal pipeline and production operations in an oilfield containing waxy crude oil, wax precipitation and deposition will occur which may provide conditions conducive for corrosion to commence. Several Niger Delta oilfields have been identified to contain waxy crude oil. Wax can be deposited in the formation, production tubing, wellhead, surface flow lines and in storage facilities, when favorable conditions of pressure and temperature exist. A decline in the reservoir pressure will lead to a decrease in production rate leading to conditions favorable for wax precipitation and deposition. This becomes a huge concern for marginal oilfields producing at low oil rates. The need to proactively predict the temperature at which wax will precipitate, called Wax Appearance Temperature (WAT), leads to the development and application of thermodynamic models for such predictions. Several models have been developed till date and are currently in use in the Niger Delta but most of them have been validated using data from stock tank oil or dead oil. This makes it unreliable for prediction of wax precipitation during production because the effects of pressure and composition have been neglected. This work aims to modify selected thermodynamic models using live crude oil data from an identified Niger Delta Oilfield with a view to mapping the Wax Deposition Envelope (WDE) which will give an idea of the WAT at different points in the production life of the field.