An Alternative to Conventional Rock Fragmentation Methods Using SCDA: A Review

Abstract

Global energy and material consumption are expected to rise in exponential proportions during the next few decades, generating huge demands for deep earth energy (oil/gas) recovery and mineral processing. Under such circumstances, the continuation of existing methods in rock fragmentation in such applications is questionable due to the proven adverse environmental impacts associated with them. In this regard; the possibility of using more environmentally friendly options as Soundless Chemical Demolition Agents (SCDAs) play a vital role in replacing harmful conventional rock fragmentation techniques for gas; oil and mineral recovery. This study reviews up to date research on soundless cracking demolition agent (SCDA) application on rock fracturing including its limitations and strengths, possible applications in the petroleum industry and the possibility of using existing rock fragmentation models for SCDA-based rock fragmentation; also known as fracking. Though the expansive properties of SCDAs are currently used in some demolition works, the poor usage guidelines available reflect the insufficient research carried out on its material's behavior. SCDA is a cementitious powdery substance with quicklime (CaO) as its primary ingredient that expands upon contact with water; which results in a huge expansive pressure if this CaO hydration reaction occurs in a confined condition. So, the mechanism can be used for rock fragmentation by injecting the SCDA into boreholes of a rock mass; where the resulting expansive pressure is sufficient to create an effective fracture network in the confined rock mass around the borehole. This expansive pressure development, however, dependent on many factors, where formation water content creates a negative influence on this due to required greater degree of hydration under greater water contents and temperature creates a positive influence by accelerating the reaction. Having a precise understanding of the fracture propagation mechanisms when using SCDA is important due to the formation of complex fracture networks in rocks. Several models can be found in the literature based on the tangential and radial stresses acting on a rock mass surrounding an SCDA charged borehole. Those fracture models with quasi-static fracturing mechanism that occurs in Mode I type tensile failure show compatibility with SCDA fracturing mechanisms. The effect of borehole diameter, spacing and the arrangement on expansive pressure generation and corresponding fracture network generation is important in the SCDA fracturing process and effective handling of them would pave the way to creating an optimum fracture network in a targeted rock formation. SCDA has many potential applications in unconventional gas and oil recovery and in-situ mining in mineral processing. However, effective utilization of SCDA in such application needs much extensive research on the performance of SCDA with respect to its potential applications, particularly when considering unique issues arising in using SCDA in different ...

The use of acoustic emissions technique in the monitoring of fracturing in concrete using soundless chemical demolition agent

“…The latter is the predominant plane of fracture, since the distance of the cylindrical hole from the side surfaces of the specimen is minimal in the y-direction, corresponding to minimal confinement from the surrounding material. These observations are in agreement with published results stating that SCDA-induced initial cracking occurs when the mean value of the tangential stress reaches the splitting tensile strength of the specimen and the crack propagation is caused mainly by mode-I type of failure [5,11,20,21].…”

“…oncrete blocks used for pavement cover were cut in prismatic shape and a cylindrical hole, of 10 mm diameter and a depth of a few cm, was drilled vertically to one of its surfaces (refer to Fig.1a). The pre-drilled hole was filled with DEXPAN soundless chemical demolition agent [5,15], in the appropriate mixing ratio of water to cementitious powder (~3.5:10), to achieve maximum expansive strenght (124 MPa, according to the manufacturer). The monitoring of concrete fragmentation in the absence of any confinement, by the AE technique was carried out at ambient pressure and temperature.…”

“…oundless chemical demolition agents (SCDAs) have been used during the last decades in the demolition of boulders and concrete structures as well as in open-surface and sub-surface rock excavation, as an effective alternative to the use of explosives posing safety risks [1][2][3][4][5]. Recently, the potential application of SCDA fracking in unconventional oil and gas recovery as well as in mineral processing applications has been under investigation [5,6]. The effect of the non-S explosive cracking agents on fracturing of the surrounding media inside a borehole is based on the volume thermal expansion of the cracking agent, caused by the exothermic hydration reaction of CaO under confined conditions.…”

“…To the best of our knowledge, these are the only available studies where the effect of SCDAs in fracturing has been studied by means of the AE technique. Although the optimum operation conditions of SCDAs, related to the external temperature, hole size and spacing, and mixing ratio of agent to water have been studied to some extent [2,11], the knowledge of the governing fracture generation and propagation mechanisms in concrete or rock masses is rather limited [5]. Regarding fracture mechanisms, quasi-static conditions can be considered in SCDA-induced rock fracturing, due to the observed stable crack propagation at low crack velocities, and micro-crack based sliding models are likely to be applied [5].…”

“…Although the optimum operation conditions of SCDAs, related to the external temperature, hole size and spacing, and mixing ratio of agent to water have been studied to some extent [2,11], the knowledge of the governing fracture generation and propagation mechanisms in concrete or rock masses is rather limited [5]. Regarding fracture mechanisms, quasi-static conditions can be considered in SCDA-induced rock fracturing, due to the observed stable crack propagation at low crack velocities, and micro-crack based sliding models are likely to be applied [5]. In this direction, the well-established monitoring technique of AE can provide valuable information on the fracture mechanisms in rocks and concrete structures under the effect of SCDAs [12][13][14].…”