Abstract
High-temperature geothermal well resource exploration faces high-temperature and high-pressure environments at the bottom of the hole. The all-metal turbodrill has the advantages of high-temperature resistance and corrosion resistance and has good application prospects. Multistage hydraulic components, consisting of stators and rotors, are the key to the turbodrill. The purpose of this paper is to provide a basis for designing turbodrill blades with high-density drilling fluid under high-temperature conditions. Based on the basic equation of pseudo-fluid two-phase flow and the modified Bernoulli equation, a mathematical model for the coupling of two-phase viscous fluid flow with the turbodrill blade is established. A single-stage blade performance prediction model is proposed and extended to multi-stage blades. A Computational Fluid Dynamics (CFD) model of a 100-stage turbodrill blade channel is established, and the multi-stage blade simulation results for different fluid properties are given. The analysis confirms the influence of fluid viscosity and fluid density on the output performance of the turbodrill. The research results show that compared with the condition of clear water, the high-viscosity and high-density conditions (viscosity 16 mPa∙s, density 1.4 g/cm3) will increase the braking torque of the turbodrill by 24.2%, the peak power by 19.8%, and the pressure drop by 52.1%. The results will be beneficial to the modification of the geometry model of the blade and guide the on-site application of the turbodrill to improve drilling efficiency.
Highlights
Hot dry rock (HDR) [1] is a renewable clean resource with abundant reserves, and the development of HDR resources can reshape the resource structure, which is beneficial to the sustainable development of the economy, resources, and the environment at large [2].The bottom of the HDR well hole is a high-temperature and high-pressure environment, and the temperature of the geothermal stratum is high, typically greater than 200 ◦ C and even up to 500 ◦ C [3]
The simulation results were compared with the performance test data of the 100-stage blades in the article by Wang [15] to verify the new method to predict the overall performance of the turbodrill
The experiment took water as the drilling fluid, the simulation material was set to 1000 kg/m3 of density
Summary
The bottom of the HDR well hole is a high-temperature and high-pressure environment, and the temperature of the geothermal stratum is high, typically greater than 200 ◦ C and even up to 500 ◦ C [3]. It is an inevitable choice to use downhole-powered drilling tools. There are two basic types of downhole driving tools: the screwdrill and the turbodrill [4]. The screwdrill has good mechanical properties, but its rubber stators cannot adapt to the high-temperature working conditions at the bottom of the hole. The all-metal turbodrill has the advantages of high-temperature resistance and corrosion resistance. It is a kind of hydraulic motor driven by the pumped fluid. Drilling fluid transfers its hydraulic power to the mechanical power of the turbine rotor while flowing through the turbine stages.
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