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Our solution required:


The CO2 levels were found to increase with depth and temperature which was consistent with the isotope analysis indicating a biogenic nature to the contamination.


The MDT pressure gradients were analysed to check if they were consistent with the recorded CO2 values. In these lean gas systems the CO2 mol% value has a large effect on the gas density. A key measurement for calculating gas densities is the reservoir temperature which is often poorly recorded.

EOS Modeling

Density predictions from high accuracy Equations of State were used to confirm the measured CO2 values. A low CO2 level was found to be insufficient to account for the measured MDT gradient.

Estimation of CO2 levels from RFT pressure Gradients

The Problem

High CO2 levels were suspected within a series of large offshore gas reservoirs. This had significant cost implications in the metallurgy requirements of subsea equipment. The recorded CO2 values were conflicting and a method was required to confirm the results.


A review of sampling and lab analyses did not reveal any systematic errors. The effect of CO2 on MDT pressure gradients was used to confirm the CO2 levels.