Karachaganak field is one of the largest accumulations of gas-condensate in the world. The field has been in production since 1985. Current development is focused on the oil rim and a gas injection programme has been implemented since 2004 using associated gas to support reservoir pressure.
The internal architecture of the Carboniferous reservoir is complex. Following deposition of the Tula shale the reservoir is characterised by an initial development of aggrading mounds followed by a progradation phase. During the Serpuhkovian, a prograding clinoform boundstone geometry is the lateral equivalent of a shallow cyclic platform dominated by grainy sediments. A more confined steep sided pinnacle complex follows as the last stage of the carbonate platform evolution.
Several environments of deposition are recognised in Karachaganak, including boundstone facies mainly deposited during the aggradation phase of the platform evolution, and the overlying cyclic platform. The target of the injectors wells is the cyclic platform, characterised by the deposition of tidal cycles which generally act as pressure baffle and lead to a high anisotropy in reservoir permeability.
The paper focuses on the geological and dynamic review of the gas Injection with the aim of improving the knowledge on gas movement and the reservoir models/predictions, and of optimizing the field development.