Fault Leakage Detection From Pressure Transient Analysis

Abstract

Leakage of reservoir fluids from injection site, e.g. through faults, is one of the key risks associated with long-term CO2 geological storage. Leakage monitoring technologies applied at different levels: in-situ, groundwater and surface, are necessary to ensure safe CO2 storage. Development and testing of the monitoring technologies is an objective of the ENOS project. In this paper, in-situ leakage detection from analysis of well bottom hole pressure is discussed. Modern CO2 injection wells are usually equipped with Permanent Downhole Gauges (PDGs), providing pressure measurements during the whole well life-span including injection and shut-in periods. A practical way to apply Pressure Transient Analysis (PTA) to such measurements for leakage detection is in the focus. A simulated well test of near-fault water injection into saline aquifer was employed to evaluate capabilities of PTA in detecting leakage through the fault. These mechanistic reservoir simulations were followed by similar simulations on an actual geological setting. A reservoir segment of the potential LBr-1 injection site containing a fault was used to demonstrate PTA-based leakage detection under actual geological conditions. Both simulation studies have confirmed that the PTA-based detection may be a useful component of the multi-level leakage monitoring technologies relying on readily available facilities (PDGs).