Experimental Investigation of Propellant Fracturing in a Large Sandstone Block

Abstract

Summary Propellants have been used in oil and gas wells to assist with perforating and creating near-wellbore stimulation. Propellants are electrically ignited in the wellbore at the perforated interval. Upon ignition, they rapidly create a large amount of gas, and the pressurization leads to breakdown of the formation. It has been postulated that the pressurization leads to creation of multiple fractures in the formation. This paper describes an experimental study with a new propellant and aims to understand the pattern of fracture creation with these propellants. The results are also compared with an older generation of propellant tested by Wieland et al. (2006). A large-scale laboratory test was performed in a sandstone block (30×30×54 in.) with a 2-in.-diameter vertical centralized wellbore extending the full block height. The block was loaded in a polyaxial stress frame. A propellant cartridge was positioned in the center of the wellbore. Small holes were drilled in the rock to intersect the expected primary fracture and were instrumented with high-resolution pressure gauges to enable fracture-timing and -growth-rate analysis. Anisotropic stresses representative of field conditions were applied on the block, and the wellbore was pressurized before ignition. The propellant ignition produced an initial peak pressure of 5,790 psi in 1.4 ms followed by an oscillatory pattern of pressure increase to a maximum pressure of 6,660 psi before decaying because of fracture growth and gas leakoff. The block was removed from the test frame and cut vertically and horizontally to examine the fracture pattern generated by the propellant. A dominant planar fracture was observed on either side of the wellbore, which propagated in the direction perpendicular to the minimum-horizontal-stress direction. It was verified that the propellant had a much-higher burn rate than the propellant tested by Wieland et al. (2006). The large-scale block test provides critical insights and data that can serve as inputs to calibrate physics-based models for modeling propellant ignition and stimulation. The results help in understanding the benefits and limitations of using propellants for stimulation.

A numerical investigation on the performance of hydraulic fracturing in naturally fractured gas reservoirs based on stimulated rock volume

“…Numerical modeling and simulation provide us an alternative to gauge the behavior of hydraulic fracture propagation in naturally fractured reservoir that cannot be substituted by small-scale laboratory experiment, where it is difficult to replicate in situ conditions with extremely high confining stress, in addition, the minimum stress tends to elevate (i.e., stress anisotropy can be much lower than designed or even disappear) during fracture propagation because of fixed displacement at the rock sample boundary (Malhotra et al 2018), and the boundary effect cannot be fully eliminated even one can maintain a constant far-field stress field during fracture propagation, and on top of that, the impact of flow-resistance-dependent fluid distribution is not able to fully manifest itself in small-scale experiment, thus, laboratory experiment has the tendency to create hydraulic fracture patterns that are more complex than what is happening in the subsurface (Law and Curtis 2002;Reinicke et al 2010).…”

An Experimental Study to Reduce the Fracture Pressure of High Strength Rocks Using a Novel Thermochemical Fracturing Approach

“…Malhotra et al [20] experimentally investigated the crack growth and pattern of multiple fractures with the new explosive material used in a propellant-based technology. They compared their results with the previously published results by Wieland et al [34].…”

“…The pulse fracturing treatment depends on many parameters such as rock strength, in situ stresses, pressurization rate, and technology in hand. Pulse fracturing is commonly known with other names such as dynamic fracturing, propellant gas fracturing, tailored pulse loading, dynamic impact loading fracturing, high energized gas fracturing (HEGF), and multiple radial stress fracturing [10][11][12][13][14][15][16][17][18][19][20]. In HEGF, the downhole combustion is initiated by both oxidizer and fuel to generate the sudden expansion of gas to quickly raise the pressure which results in synthetic sweet spot.…”

Improving the controllability and effectiveness of the chemical-technological process of the technology for hydrogen thermobaric chemical stimulation of hydrocarbon recovery

“…Another modern direction of processing the bottom-hole formation zone of a well with the aim of stimulation is the use of chemical energy sources to create both mechanical and thermal effects on the formation. The use of propellants (components of rocket fuels) [8], which are ignited in the bottom-hole zone of the well, can be quite promising. During combustion, a large number of gases are formed that break the formation.…”