SYSTEMS, METHODS, AND COMPUTER-READABLE MEDIA FOR CONTINUOUS CAPILLARY PRESSURE ESTIMATION

摘要

Provided are methods, systems, and computer-readable media for determining capillary pressure in a basin/reservoir. Well log data is obtained that includes permeability log data, porosity log data, water saturation log data, and oil saturation log data. Thomeer parameters for a multi-pore system of a Thomeer model are determined by evaluating an objective function that measures the mismatch between the well log data and modeled data having the Thomeer parameters as input. The objective function is iteratively evaluated using linear equality constraints, linear inequality constraints, and nonlinear equality constraints until convergence criteria are met.

主权项

1. A computer-implemented method for determining capillary pressure in a reservoir, the method comprising:
accessing well log data from a well log for a well, the well log data comprising permeability log data, porosity log data, water saturation log data, and oil saturation log data; determining Thomeer parameters from the permeability log data, the porosity log data, the water saturation log data, and the oil saturation log data, the Thomeer parameters comprising a fractional bulk volume, a pore geometrical factor, and a minimum entry pressure, the determining comprising:
determining a modeled permeability;determining a modeled porosity;determining a modeled water saturation, andevaluating an objective function based on one or more linear equality constraints, one or more linear inequality constraints, and one or more nonlinear equality constraints, the objective function comprising:F(T)=w2(1-SwFAL)-So(T)2+(1-w)2T-T^2 wherein T is the Thomeer parameters,
SwFAL is the value of the water saturation data,So(T) is a modeled oil saturation;the one or more linear equality constraints comprising:∑i=1nBvi(Pc)=α*φFAL wherein Bvi is a fractional bulk volume occupied by mercury,
Pc is an applied capillary pressure;α is the conversion factor from mercury-air to oil-water,n is the number of pore systems in the reservoir,φFAL is the porosity data;the one or more linear inequality constraints comprising:
Bvimin≦Bvi(Pc)≦Bvimax for 1≦1≦n Gimin≦Gi≦Gimax for 1≦i≦n wherein Gi is the pore geometrical factor,
Pdimin≦Pdi≦Pdimax for 1≦i≦n wherein Pdi is a minimum entry pressure,
If Bvi(Pc)≠0 then Bvi+1(Pc)Bvi(Pc) for 1≦i≦n−1,Pdi≦Pdi+1 for 1≦i≦n−1, andthe one or more nonlinear equality constraints comprising:
K(T)=KFAL wherein K(T) is the modeled permeability,
KFAL is the permeability log data; and determining the capillary pressure of the reservoir using a Thomeer model having the determined Thomeer parameters.