Novel Algorithm to Quantify Productivity of Multi-layered Gas Condensate Heterogeneous Reservoirs

Abstract

Abstract Performance prediction of multi-layered gas condensate reservoirs is challenging in order to maximize the recovery and operate gas wells effectively. Gas condensate reservoirs may undergo liquid condensation without significant liquid production at the surface. Pressure decline and skin are the main factors that cause condensate banking around the wellbore resulting into loss in well deliverability. In this study our key objective is to investigate the effect of multi-layered system on gas condensate productivity and to develop a novel empirical algorithm to quantify productivity of multi-layered gas condensate heterogeneous reservoirs. This paper describes the potential benefits of establishing a new algorithm that considers the effect of different permeability layers in the system. The concept of semivariogram function has been introduced to take into account the effect of reservoir heterogeneity. Most of the previously developed empirical models are for conventional homogeneous or naturally fractured gas condensate reservoirs. The results of this work are obtained from a 3D reservoir simulation model built using a commercial reservoir simulator. A base case is modeled with radial reservoir and simulation model is developed using black oil formulation with characteristic rock, fluid and reservoir properties. Logrithmic radial grid distribution is used for single well modeling. Vertical well is placed at the center of the reservoir. Reservoir heterogeneity is included in the simulation model utilizing semi-variogram function. Dimensionless inflow performance relationship (IPR) curves are generated by plotting flowing bottomhole pressures versus gas production rates in a dimensionless form. Non-linear regression techniques are applied to fit dimensionless flowrate as a function of dimensionless pressure. Sensitivity analysis of different parameters like porosity, reservoir temperature and vertical permeability on generated inflow performance curve is also performed. The results are analyzed, converged and validated. The generated novel empirical algorithm was found giving accurate results with less than 2% error when compared to other existing models. The new IPR is very useful in improving the flow rate and modeling gas condensate reservoirs when we have multi-layered systems.