A delicate calculation method for reservoir initial water saturation based on a novel approach to J-function...

Area of Science:

• Petroleum Geoscience
• Reservoir Engineering
• Sedimentary Geology

Background:

• Accurate initial water saturation (Sw) is critical for reservoir assessment and development.
• Conventional J-function methods suffer from curve fitting variability, suboptimal sample grouping, and limited core data.
• Heterogeneity in reservoir samples complicates traditional water saturation calculations.

Purpose of the Study:

• To develop an improved J-function method for accurate water saturation estimation.
• To address limitations of conventional J-function analysis, including sample heterogeneity and grouping issues.
• To establish a continuous, tailored calculation method for water saturation in reservoirs.

Main Methods:

• Analysis of 55 J-function curves from Iraq's Zagros Basin Reservoir N.
• Classification of J-function curves into power and exponential types based on permeability thresholds.
• Development of improved J-function models correlating coefficients with Reservoir Quality Index (RQI).

Main Results:

• Permeability identified as the primary factor influencing J-function curve shape.
• A novel permeability-based classification method for J-function curves was established.
• The improved J-function method provided more accurate Sw estimates compared to Archie and conventional J-function, especially in heterogeneous reservoirs.

Conclusions:

• The developed method offers a robust framework for continuous, tailored water saturation calculations, eliminating the need for sample grouping.
• The improved J-function method accurately estimates water saturation in both high-quality and poor-quality reservoir intervals.
• This approach enhances reservoir resource assessment and development optimization through precise initial water saturation determination.