The Application of CT Scanning in Visual Plugging Evaluation

In order to obtain a plugging formula that better conforms to the ideal filling particle size distribution curve, this study first determined the optimal particle size characteristic value, D<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">90</inf>, through true triaxial large-scale model plugging experiments, that is, when it is 0.8 times the fracture width, the bridging plugging effect is optimal. Furthermore, utilizing a 3D printing fracture plugging evaluation device, the 0.6/0.8 times fracture width benchmark condition was established, and two groups of sealing body were prepared for 5mm wide fractures. Through CT scanning and three-dimensional reconstruction technology, a detailed analysis of the two groups of sealing body was conducted, revealing that in the experiment where D<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">90</inf> equals 0.8 times the fracture width, the particle size of the sealing body was larger, and the bridging position was more forward. In addition, the reliability of the CT scanning method was verified by comparing the particle size distribution of the formula with the particle size obtained from CT scanning. Based on the above optimization results, we conducted further optimization experiments on the formula for 5mm wide fractures using the visual plugging evaluation device. According to different particle sizes, the plugging materials formula was divided into primary, secondary, tertiary, and filling grades, and graded optimization was performed. The final optimal formula was determined to be 0.38% (3-4 mesh) + 1.62% (4-5 mesh) + 1.53% (5-6 mesh) + 5.82% (6-8 mesh) + 2.45% (12-16 mesh) + 0.67% (20-24 mesh) + 0.56% (24-28 mesh) + 0.30% (28-32 mesh) + 6.67% (SQD-98 fines), with a pressure resistance of up to 3MPa and a leakage volume of only 400mL. The experimental results further analyzed the working mechanism of the plugging materials inside the fracture and the formation process of the sealing body. The achievements of this study provide important parameter support for the design of on-site plugging construction formulas, with significant practical value and theoretical significance.