Dynamic Fracture Width Calculation for Drilling Fluid Loss
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Solution Overview
Problem
Current methods for calculating fracture width in fractured formations during drilling are inaccurate due to the coupling effects of non-Newtonian flow characteristics and deformation characteristics, as well as the roughness of fracture surfaces, leading to inefficiencies in designing loss-proof and plugging formulas.
Innovation Solution
A dynamic fracture width calculation method that considers dynamic changes in fracture widths and roughness of fracture surfaces, using seismic data and fracture development characteristics to select models and calculate static and dynamic hydraulic widths, ultimately converting these to mechanical widths for designing effective plugging formulas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional loss fracture width calculation models are used, then the calculation process is simple, but the accuracy of fracture width calculation is reduced due to coupling effects of non-Newtonian flow characteristics and deformation characteristics
Solution Approach 1:
The patent transforms the static fracture width calculation into a dynamic calculation that accounts for real-time changes in fracture width under varying stress conditions. The model dynamically adjusts fracture width based on effective stress, non-Newtonian fluid characteristics, and roughness effects, resolving the contradiction between calculation accuracy and model simplicity.
Solution Approach 2:
The patent introduces multiple variable parameters including effective stress, fluid rheology parameters, and roughness coefficients to accurately capture the coupling effects. By systematically varying these parameters in the calculation model, the patent achieves high accuracy in fracture width prediction while maintaining a structured approach to model complexity.
2Reliability
If plugging materials are selected based on inaccurate fracture width calculations, then the design process is quick, but the performance of the plugging formula is reduced due to mismatch with actual fracture conditions
Solution Approach 1:
The patent performs preliminary calculation of dynamic fracture width and mechanical width distribution before selecting plugging materials. This advance calculation provides accurate guidance for material selection, ensuring the plugging formula is optimally matched to actual fracture conditions while streamlining the overall design process.
Solution Approach 2:
The patent establishes a feedback mechanism where calculation results inform material selection, and material performance data can be used to refine future calculations. This closed-loop approach ensures continuous improvement of plugging formula performance while reducing trial-and-error iterations.
3Measurement precision
If the roughness of fracture surfaces is not considered, then the calculation model is simpler, but the accuracy of fracture width calculation is significantly reduced
Solution Approach 1:
The patent incorporates roughness effects through local quality adjustments to the fracture width calculation. By introducing roughness coefficients and mechanical width distribution concepts that account for local surface variations, the model achieves high accuracy without requiring complete geometric reconstruction of the rough surface.
Solution Approach 2:
The patent uses mechanical width as an intermediary parameter that bridges the gap between hydraulic width (easier to measure) and actual flow characteristics (affected by roughness). This intermediary concept allows the model to account for roughness effects indirectly, maintaining simplicity while improving accuracy.
Data Source
AI summary
The invention relates to a dynamic fracture width calculation method for drilling fluid loss in a fractured formation, which belongs to the field of loss control of drilling and well completion engineering, and includes the following steps: selecting a model according to seismic data and fracture development characteristics and calculating a static hydraulic width of a formation fracture; substituting the static hydraulic width of the formation fracture into a deformation formula of a fracture hydraulic width, to obtain a dynamic hydraulic width of a wellbore fracture; converting the dynamic hydraulic width of the wellbore fracture into an average mechanical width of the wellbore fracture, according to a conversion relational formula of a mechanical width; and solving a mechanical width distribution range of the fracture according to a standard deviation of a mechanical width distribution of a natural fracture.