Size Effect of the Length-to-Diameter Ratio of Pipelines on the Methane/Air Explosion Pressure.

Abstract

To overcome the shortcomings inherent in hydraulic fracturing technology, including water wasting and contamination, in situ methane explosive fracturing technology has been put forward. Yet the realization of this technology strongly depends on the creation of high explosion pressure. In this work, the relationship between the length-to-diameter (<i>L</i>/<i>D</i>) ratio of pipelines and the maximum explosion pressure of methane/air has been numerically explored and experimentally verified. The results show that there exists an optimal <i>L</i>/<i>D</i> ratio that can significantly increase the explosion pressure of methane/air by about 50%. For instance, under atmospheric (reference) pressure, the explosion pressure has been enhanced from 0.787 to 1.193 MPa by varying the <i>L</i>/<i>D</i> ratio from 10 to 20. Additionally, both the optimal <i>L</i>/<i>D</i> ratio and the maximum explosion pressure are dependent upon the initial pressure and basically follow a logarithmic and linear function of initial pressure by proposing two fitted equations. After the initial pressure has increased to 10.1 MPa, an optimal <i>L</i>/<i>D</i> ratio of 120 can cause an explosion pressure of up to 124.287 MPa. The methods of optimizing the pipeline <i>L</i>/<i>D</i> ratio applicable in the in situ methane/air explosive fracturing are thus proposed, which can provide theoretical insight for fracturing shales.