Measuring inter-reservoir cross flow rate through unintended leaks in zonal isolation cement sheaths in offset wells

Abstract

Crossflow between two adjacent reservoir layers through leaky cement sheaths in offset wells during transient-pressure tests in one of the two reservoir layers is diagnosed and quantified. The obtained measures are determined based on individual well and layer properties. The pressure drawdown in the reservoir layer in which pressure transient testing is being performed is measured as a function of time. The longitudinal conductivity of a leaky cement sheath in an offset well and the pressure drawdown in the tested reservoir layer simultaneously control the crossflow rate to the tested reservoir layer from the adjacent reservoir layer at a given time.