Method for evaluation of oil displacement coefficient based on conventional core analysis

Abstract

The article is devoted to the problem of evaluation of oil displacement coefficient. Determination of oil displacement coefficient is essential stage for estimation of recoverable reserves, feasibility study of oil recovery factor and control of field development. Complexity of its laboratory determination is caused by labor intensity and duration of a process. When the number of cores is not enough for flow experiments or absent oil recovery factor is evaluated either similarly to neighbor fields or by analytical dependencies that are important to obtain. During the generalization and analysis of a significant amount of experimental data the authors developed a method for estimation of oil displacement coefficient without its laboratory determination. A proposed method is based on use of data from previous studies to built statistical models for estimation of displacement coefficient using linear step-by-step regression and discriminant analysis. In order to implement the method along with oil viscosity, knowledge of reservoir parameters such as porosity, permeability, irreducible water saturation and bulk density of a rock, determined by conventional core studies, is required. The main stages of implementation of the method for Visean clastic deposits of the Bashkir arch and Solikamsk depression of the Perm Region are presented. Results of implementation of the method for Bashkir carbonate deposits of the indicated tectonic elements are presented as well. Analysis of initial data allow establishing that there are classes of values for which regression equations are statistically justified. According to the equations model and experimental values of the displacement coefficients are very close to each other. It was concluded based on parameters of the equations that there is abnormal influence of initial oil saturation on the displacement coefficient. It is shown that for reservoirs of low flow characteristics a displacement coefficient is determined by their capacitive properties.

Keywords

• oil displacement coefficient
• core
• analytical dependence
• discriminant analysis
• regression analysis
• statistical model
• oil viscosity
• porosity
• permeability
• irreducible water saturation
• rock bulk density
• conventional core analysis
• clastic deposits
• carbonate deposits
• regression equation