DEFINITION AND DESCRIPTION OF THE OIL AND GAS RESERVOIR CONNECTIVITY COEFFICIENT

Abstract

The relevance of the research is caused by the need in quantitative evaluation of reservoir connectivity of models for classifying realizations in multivariant modelling and optimization of selection of methods and parameters for reservoir geomodelling. The main aim of the research is to define connectivity coefficient and estimate its representative validity for different size and geometry models; to evaluate impact of reservoir heterogeneity parameters on connectivity coefficient value. Objects of the research are geological and simulation models of oil and gas reservoirs. Methods of the research are geological modelling and reservoir simulation, statistical analysis of the results of geomodeling and reservoir simulation. Results. The paper briefly describes the existing methods for evaluating the connectivity of oil and gas reservoirs and new approach to connectivity estimation. New connectivity coefficient is defined as a ratio of model liquid rate to unit model liquid rate. Unit model means that net to gross ratio value for all cells is 1 and the model provides maximum possible liquid rate. The paper considers the impact of the model geometry and scale on the connectivity coefficient value. The authors have studied the relation of connectivity coefficient to net to gross ratio, variogram ranges and anisotropy, nugget effect. The connectivity coefficient was stated as a variable, which characterizes the ability of reservoir to pass fluid independent of absolute and relative permeability, porosity, transmissibility etc. The connectivity coefficient as opposed to percolation theory methods can provide continuous evaluation of fluid flow between model cells and does not require valid production history of reservoir.

Keywords

• geomodel
• reservoir connectivity
• connectivity coefficient
• variogram
• nugget effect
• sequential indicator simulation
• percolation
• multiwell productivity index