Tengiz Sour Gas Injection Modeling: A Geo-mechanics Approach to Understand Gas Breakthrough

Abstract

Abstract Tengizchevroil (TCO) uses sour gas injection technology in a limited area of the Tengiz field in Kazakhstan (giant carbonate sour oil field) for pressure management and sour gas re-injection. Several sour gas injectors have been drilled and operated since 2007. A recent operational question is whether gas breakthrough is caused by fracturing induced by cold gas injection. Additionally, there is an interest in knowing the injection limits that do not result in induced fracturing. In this paper, numerical modeling of sour gas injection using a geomechanics simulator is employed for the simulation of the Tengiz field sour gas injection. The aims are to investigate the potential of gas breakthrough and especially the effects from fracturing induced by cold sour gas injection. Historical injection rate and pressure data are used to calibrate the numerical model. Given the complexity of the field geological features, a sensitivity study is performed for future forecast. Critical parameters investigated include injection rate, injection temperature, stress, permeability, etc. The study considers a wide variability of the input values to fully evaluate the effect of gas injection. The results of this study provide valuable guidance for TCO's sour gas injection strategy design which may impact future expansion of gas injection in addition to better performance towards operational excellence of the injection/production plan.