Modeling and optimization of mechanical properties of drilling sealing materials based on response surface method

Abstract

To improve the sealing effect of a borehole and the efficiency of gas extraction, an ideal ratio of modified materials is needed to provide the optimal strength effect of the borehole sealing material. In this study, the influence of fly ash (Fa), nanosilica (nanoSiO2), and triethanolamine (TEA) on the compressive strength of cement was analyzed using a single-factor experiment. A quadratic polynomial regression model of yield stress was developed using the response surface method (RSM); the influence on the material strength based on the interaction among the three modified materials was analyzed. The optimal ratio of the three components was determined to be 5.8% Fa, 3.6% nanoSiO2, and 0.044% TEA using RSM; from this, the predicted 28 d strength was calculated to be 57.26 MPa. The experimental 28 d strength of the optimized material was determined to be 55.44 MPa; this produced an experimental error of 3.2%. The experimental strength of the optimized material was 41.14% higher than that of the blank group. In the optimized material, the Ca(OH)2 content was reduced by 0.755%, and the needle-rod ettringite (AFt) and calcium silicate hydrate (C–S–H) contents were significantly increased. The microscopic morphology was flatter and denser. This indicated that the synergistic effect of the three modified materials optimized the hydrate fraction and dense material structure; this caused an improvement in the compressive strength of the material. This work has substantial application in the development of new drilling sealing materials that promote efficient extraction and utilization of coal mine gas.