Leakage Fingerprints During Storage: Modeling Above-zone Measurements of Pressure and Temperature

Abstract

Since non-negligible leakage rates from injection and storage zones are possible along wellbores, it is important to be able to diagnose whether leakage is occurring. We show that concurrent pressure and temperature measurements are especially valuable because they independently constrain the effective permeability of a leakage path along wellbore. We describe a set of coupled analytical models for identifying the characteristic features of wellbore leakage in above-zone monitoring data. Application to data from an observation well (EGL7) during two years of steady CO2 injection in Cranfield (Mississippi, USA) shows that the observed pressure elevation requires an extremely large leakage rate, and that this rate would be large enough to raise the temperature in the monitoring zone significantly. Because the latter temperature “fingerprint” is not observed, we conclude that the observation well is unlikely to be leaking.