Predicting porosity in tight sandstone reservoirs based on logging while drilling engineering parameters

Area of Science:

• Geology
• Petroleum Engineering
• Drilling Engineering

Background:

• Reservoir porosity is vital for oil and gas exploration and development.
• Current methods for porosity acquisition (core testing, logging) lack real-time quantitative evaluation during drilling.
• This limitation hinders timely and efficient porosity data acquisition.

Purpose of the Study:

• To develop a real-time quantitative prediction method for reservoir porosity in tight sandstone reservoirs.
• To investigate the relationship between drilling parameters and reservoir physical characteristics.
• To establish a porosity prediction model based on drilling and logging engineering parameters.

Main Methods:

• Modeling and rock-breaking simulations of 5-blade and 6-blade Polycrystalline Diamond Compact (PDC) bits.
• Analysis of drilling parameters like Rate of Penetration (ROP), torque, and Mechanical Specific Energy (MSE).
• Development of a physical index to reflect formation characteristics, independent of bit type.

Main Results:

• ROP, torque, and MSE are influenced by bit type and unsuitable for direct porosity prediction.
• The physical index shows a consistent logarithmic relationship with elastic modulus for different PDC bits.
• A power-law relationship was established between porosity and the physical index, using elastic modulus as an intermediary.

Conclusions:

• The developed physical index effectively eliminates bit influence, accurately reflecting formation characteristics.
• The real-time porosity prediction method achieved over 91% agreement in cross-verification and 85% average consistency in exploration wells.
• This method provides timely, efficient, and accurate support for exploration decision-making.