Summary In this paper, a generic thermal/mechanical interaction model was developed to predict the penetration rate and mechanical damage around perforation tunnels that resulted from the laser perforation of rock samples. The perforating process is driven by heat emitted by a laser beam directed at the surface of a sample. The temperature propagation, thermal expansion, and thermal/mechanical interaction were modeled by coupling heat conduction in solid media with the elastic/plastic constitutive mechanical response of rocks. The phase changes that occur during the melting and evaporating process were accounted for in the latent heat of fusion and of vaporization. The heating boundary was updated dynamically along with the evolution of perforation channels. The model was used to parametrically investigate the effects of material properties, stress ratio, and laser–beam characteristics on the penetration rate and mechanical damage.
Laser applications provide unique advantages to applications in discovery, recovery, and production of hydrocarbons. A comprehensive numerical model would enable prediction, optimization, increase efficiency, enhance control, and further innovation. This work reviews the modeling methods, discusses key variables and physics, presents results, and introduces innovative solutions that make use of machine learning and artificial intelligence to solve an inherently multi-scale and multi-physics problem. Two possible methods have been explored to model laser-rock interaction: mechanistic and statistical — the former uses as a set of coupled partial differential equations that adequately describe the physics involved. The statistical method uses advanced statistical analysis and supervised-learning to elucidate relations between the experimental settings and observations. The full-physics or mechanistic model was developed using finite-element and finite-difference methods; it incorporates coupled solvers for electromagnetic, thermodynamics, and geomechanics. The statistical model uses advanced statistical analysis and machine learning to characterize the dynamics and build a prediction algorithm. A numerical model of laser-rock interaction must comprise physical dynamics that span over different time and spatial scales. When a laser beam impinges on a rock, a portion of the incident energy is absorbed as thermal energy, and a thermal gradient is created. The result is a distribution of physical and chemical changes such as spallation, melting, dissociation, calcination, or vaporization. The full-physical model can adequately capture the transient process; however, it requires a functional characterization of the dynamic rock properties, environmental conditions, and laser parameters. The statistical approach provides a prediction of the overall outcome of the process departing as a function of known input parameters, yet its precision depends on the availability of experimental data (outcomes and conditions). Key parameters are identified using statistical analysis. The modeling results agreed with experimental tests. Further, they evince that thermal properties and geomechanical stresses configuration have a significant impact on the process’ outcome. These methods can optimize and predict the interaction for multiple applications, ranging from heat treatment to stimulation. Subsurface laser operations could provide the next generation of stimulation and workover tools for Oil and Gas. Numerical models of laser-rock interaction are essential to predict, optimize, adapt, and evaluate subsurface laser applications during development, test, and operation. This work provides a basis for the development of future numerical models and enables the next generation of subsurface photonic tools.
The objective of this study is to provide an overview of recent waterless stimulation focusing on hydraulic fracturing technologies, advantages and disadvantages, limitations, and new technologies under development. Different technologies are presented including proppant-free such as slurry fracturing and in-situ proppant generation, CO2, LPG, Seawater, plasma fracturing, high power lasers, gas stimulation, exothermic reactants, and high energy gas fracturing. Water-based hydraulic fracturing is commonly used stimulations to recover hydrocarbon specifically from the tight formation. The unconventional reservoir requires pumping and fracturing multistage to maximize stimulated reservoir volume. This technology involves the use of large volumes of high water quality, pumping at high pressure, and filling up the fractures with proppants. Several technologies are presented in an effort to find alternatives to current water-based fracturing technologies. The industry efforts towards waterless fracturing technology are to adapt different technologies into fracturing, for example, the use of plasma to create fractures. The principle of this technology is to store large electric charges and release them in a very short period. Another technology is based on gas combustion to create pressurized gas, which can then create fractures in the reservoir, the use of high-energy laser is used for fracture initiation, and in-situ proppants are targeting chemicals that generate proppant in the fractures. Jetting is also evaluated where acid is injected at a high rate for deeper penetration to create network tunnels. Exothermic fracturing is also discussed which is a technology based on chemical reactions that are triggered at downhole temperatures releasing pressurized gases and creating fractures. Once the drilling operations of a well are concluded, the well is then completed and stimulated. A typical scenario is to perforate the well using a shaped charge perforating gun followed by acid or hydraulic fracturing to maximize reservoir contact. A considerable reduction in permeability can occur when using conventional shaped charge gun, when the fracturing fluid formulation is not appropriately designed, or when improperly flowing back the fracturing fluids. A thorough investigation of recent non-damaging waterless stimulation technologies is included as an alternative to shaped charge gun perforation or to fracturing with water. If conventional fracturing is to be used regardless, then these technologies can be used to help initiate the fracture by lowering the formation breakdown pressure. In addition, it is possible to use these technologies in producing wells to enhance productivity. The discussion will provide details of each technology: suitable use scenario, methodology of use, limitations, and results of case studies. As more and more wells require stimulation to be produced commercially, new non-damaging waterless methods are implemented. The importance of this paper is to show these alternative technologies to increase production and minimize damage to reservoirs.
This paper presents the strategy and execution that led to the industry's first successful deployment of a high-power laser in the field. The development encompassed various aspects: administration, technical, lab-to-field transformation, and intensive research. One of the primary success factors was identifying potential technologies and forecasting their evolution. High-power lasers were selected for the upstream applications because of their capabilities and successful use in almost every industry, ranging from medical to the military; it attracted the industry due to its unique features, such as precision, reliability, control, and accuracy. High-power lasers at the early stage (generation) were not applicable for downhole applications due to their relatively lower power levels. However, it has been utilized widely in several applications, such as sensing, measurements, and others. The objective of this program is to utilize the new generations of higher-power lasers in several upstream applications. The program is strategically designed to reduce the risk and increase success. In the initial stage, the work focused on the feasibility and characterization of intervening physics. The goal was to answer fundamental technical questions, such as "can lasers penetrate all types of rocks? What are the limitations? What is the effect of the laser on rocks?" The research spanned the last two decades, culminating in the development of the first field prototype of a high-power laser system. The work proved that near-infrared multi-kilowatt lasers (hereon high-power lasers or HPL) could perforate and process any rock type at different conditions, including in-situ testing and liquid environments. The experimental plan was designed systematically and divided into phases, starting from fundamentals to advance. Prototype tools were designed, tested, and upscale for field deployment. All applications can be performed with the same HPL source -only the optical head needs to be changed. High-power laser technology is an alternative to conventional methods of subsurface energy extraction, such as perforation, descaling, and drilling. It is cost-effective, compact, versatile, waterless, energy-efficient, and environmentally friendly, thus enabling sustainable field operations.
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