Research and application on megawatt level intelligent fracturing pump system in coal mine

This paper presents the development of a megawatt-scale intelligent fracturing pump system for underground coal mines, designed to address the escalating demands for flow and pressure in large-scale regional fracturing applications, particularly in hard roof management and enhanced gas extraction permeability. The system integrates automatic control and variable frequency technology with the design of underground coal mine fracturing pumps, enabling dynamic collection of performance parameter data at various stages of hydraulic fracturing. It provides real-time analysis of the power matching for electrically driven fracturing pumps and achieves full automation of the fracturing process. Key technological challenges, such as the development of special materials for high-pressure, high-flow-rate fracturing pumps; the reliability of the transmission system and hydraulic ends for megawatt-level fracturing pumps; and intelligent control technology, have been successfully addressed. The research included: Development of high-strength, erosion-resistant martensitic precipitation hardening stainless steel suitable for extreme conditions with large flow, ultra-high pressure, and sand-mixed media, along with ultra-high pressure self-reinforcing treatment to enhance the fatigue life of the hydraulic ends of fracturing pumps; Investigation of critical reliability technologies, including high-strength welding for alloy steel, high-load-bearing, high-power-to-weight ratio gear transmission technology, and wear-resistant friction pairs of aluminum bronze alloy-cast iron, to ensure the reliability of the transmission system under high-power conditions; Creation of a high-durability metal plunger-combination seal fracturing fluid sealing pair, with the application of computer simulation technologies such as virtual prototyping, FEA, CFD, and hydraulic system simulation to optimize the structure, performance, and reliability of the fracturing pump’s fluid end suction and discharge systems; Mastery of technologies such as low-frequency variable flow sealing for deep boreholes, automatic identification of coal and rock layer fracturing, and cyclic fracturing control, enabling intelligent control throughout the fracturing process. The industrial trial of this system has been successfully conducted at the Caojiatan coal mine 122110 extra-thick coal mine working face for weak zone management of hard roof strata and at the Dongli coal mine 1250 gas control lane for high-efficiency extraction of anti-reflection gas in coal seam areas. Field tests demonstrated that at the Caojiatan coal mine, pre-splitting treatment for hard roofs achieved stable fracture expansion pressure with a maximum of 32.4 MPa and an average flow rate of 100 m3/h. At the Dongli Coal Mine, the gas permeability enhancement test revealed that after 10 days of hydraulic fracturing, the average pure gas extraction volume increased to 1.596 m3/min, approximately 29 times that of the conventional drilling extraction process.