Abstract
The objective of the study is analytical modeling of a dry gas reservoir, with more than 30 drilled wells and 15+ years of production history, underlain by thick tight gas zone, that is highly compartmentalized (both structural and stratigraphic) and heterogenous (laterally and vertically).
The multi tank material balance model is created to address the major uncertainties within the compartments such as Fault Transmissibility, Aquifer Strength, Early Water Influx, Tight Gas Support, and its quantification by the integration of all the geological, fluid, rock, pressure, and the production data. Some of the structurally up-dip wells are watered out however down-dip wells continue to produce gas at reasonable rates with complete stability in the reservoir pressure.
The model has been history matched with multiple scenarios and showed that the pressure recharging observed in a certain compartment is from an additional GIIP feeding into the compartment through the underlying tighter zone rather than laterally from the other compartments. A weak aquifer encroachment in the same compartment is from an adjacent compartment having moderate water drive through fault breach.
Compartments are history matched with adequate pressure and Water Gas Ratio (WGR) by manipulating productivity indices for individual wells, modifying aquifer strength, inter-compartment transmissibility, pseudo relative permeability curves and impact of tight gas recharging. The quantitative estimation of minimum connected GIIP is performed by balancing the support through encroaching aquifer and tight gas recharging.
The scope included the estimation of the minimum connected Gas Initially in Place (GIIP), ascertain aquifer strength and direction as well as pressure recharging within the different compartments using pressure and production data. The study assisted in capturing the communication between the compartments and evaluation of remaining potential of the field. The results would then be used in subsequent numerical modelling with the possibility of increasing overall recovery from the field.
