ESTIMATING IN-SITU RELATIVE PERMEABILITY AND CAPILLARY PRESSURE FROM MULTIPHYSICS WIRELINE MEASUREMENTS

摘要

We present a comprehensive workflow, in the presence of water-based-mud drilling fluids, to estimate in-situ relative permeability and capillary pressure curves by integrating multiphysics wireline measurements including array resistivity, dielectric, nuclear magnetic resonance (NMR), and formation testing and sampling data. Array resistivity logs are used for estimating the radial invasion profile and formation connate water saturation. Dielectric logs have shallow depths of investigation and hence are ideal for estimating residual oil saturation. Also, they provide vital information for determining Archie’s parameters ğ‘š and ğ‘›. NMR data are used to estimate irreducible water saturation, and from the T_2 distribution, we can estimate a pore size distribution index (PSDI), which can help constrain the solution when inverting for relative permeability and capillary pressure curves. NMR data can also be input to the computation of a continuous permeability log that can be calibrated to permeabilities from cores or formation tests. Based on the derived PSDI, we can further narrow the physical bounds for Corey’s exponents in the relative permeability model, i.e., the curvatures of relative permeability curves for the water phase and the oil phase. This workflow demonstrates an efficient method to obtain in-situ relative permeability and capillary pressure parameters, which can help fill the gap in reservoir modeling and simulation. The method has been successfully applied to different reservoir formations including shaly sands, carbonates, and unconsolidated siliciclastic reservoirs.