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Abstract Until now, hydraulic fracturing has played prominent role in increasing production of hydrogen energy such as natural gas, geothermal energy, natural gas hydrate. Hydrogen energy stimulation is realized by many methods. Such as multiple-clusters in staged fracturing, and fracture propagation guided by combined radial boreholes in different azimuths. In order to extend lateral stimulation area, the zipper fracturing is investigated continuously. However, the report on the zipper fracturing is limited to the post-frac productivity. In this study, model of simultaneous and zipper fracturing was established in ABAQUS to investigate the effect of six factors on the fracture propagation. The results showed that in simultaneous fracturing, the fracture network is formed spontaneously. With same brittleness of reservoir, fracture in zipper fracturing always propagates slightly longer than that in simultaneous fracturing. The results provide theoretically support for both fracturing modes, which helps design of well completion and fracturing operation parameters. Highlights • The effects of multiple factors on fracture propagation of the new crafts on hydraulic fracturing was studied. • Simulation experiments of zipper fracturing were in-depth carried out. • Simulation of fracturing cracking stress was studied. • Difference of fracture propagation between simultaneous fracturing and zipper fracturing was discussed. [ABSTRACT FROM AUTHOR]

Abstract Conventional hydraulic fracturing fails to develop low permeability reservoirs of fossil hydrogen energy that are not located in the direction of maximum principal in-situ stress. A new technology of fracture propagation guided by radial holes is proposed, which can realize directional propagation of hydraulic fracture along radial holes in fossil hydrogen energy development. In order to verify this new technology, a model of radial holes combined with hydraulic fracturing is established by the ABAQUS extended finite element method. Simulation results show that radial holes play a guiding role in fractures propagation. The influence extent of seven factors on the directional propagation of hydraulic fracture is listed as follows (from strong to weak): azimuth of radial holes > horizontal in-situ stress difference of fossil hydrogen reservoir > injection rate of fracturing fluid > Young's modulus of rock > permeability of fossil hydrogen reservoir > Poisson ratio of rock > viscosity of fracturing fluid. True tri-axial experiment is carried out to verify the accuracy of numerical simulation, and the result is consistent with numerical model, which indicates that numerical simulation is reliable. Highlights • A three-dimension stress coupled seepage model of radial holes is established. • Numerical model proves that radial holes play a guiding role in the directional propagation of hydraulic fractures. • The influence of seven factors on directional propagation of hydraulic fracture guided by radial holes is analyzed. • Tri-axial hydraulic fracturing experiment is carried out to verify the accuracy of numerical simulation results. [ABSTRACT FROM AUTHOR]

Hydraulic fracturing of radial wells have become new technologies to effectively develop low permeability reservoir, thin reservoir, fractured reservoir, “dead area” after water injection etc. Influenced by ground stress and reservoir heterogeneity, hydraulically created fracture will probably not extend smoothly to connect the target area along the direction of radial wells, the reservoir stimulation effect is not ideal. Based on the pressure analysis of fracturing initiation of multiple radial holes and the theory of plasticity district, criterion of multiple radial wells orientating directional fracture propagation in the condition of ground stress is derived. In this condition, multiple radial wells will produce a continuous plasticity district in the reservoirs, while maintaining the fracture extending in plastic zone directionally without the effect of ground stress, which guarantees that fracture is interconnected between the radial wells during fracturing operation, to form the main crack along the direction of radial wells’ axis plane. In consideration of economy, maximum spacing of radial wells are optimized, in order to provide a reliable scientific basis for effectively implementation of hydraulic fracturing technology in radial wells. [ABSTRACT FROM AUTHOR]

Water cut is generally rising with the increase of water injection during water flooding development of fossil hydrogen energy reservoir. Conventional chemical profile control agents fail to work for a long time because they are easily affected by the temperature and salinity of fossil hydrogen energy reservoir to form crossflow channel. In this paper, a new dual-disperse profile control agent and flooding system (DDS) is proposed, which uses polymers and microspheres to plug polymer crossflow and improve oil recovery in fossil hydrogen energy development. The viscosity, suspension property, thermal stability and microsphere size expansion of the DDS are tested, and the oil displacement performance is evaluated. The results show that the viscosity of polymer solution is not affected by the addition of microspheres, and the DDS system has good suspension and thermal stability. Due to the adsorption of microspheres in polymers, the particle size of microspheres tends to increase with time. But the expansion slows down gradually, which is beneficial to deep migration. In terms of plugging efficiency, the optimum concentration of DDS is 1500 mg/L polymer and 500 mg/L microsphere, and the optimum injection volume is 0.5Pv. Compared with single polymer flooding system, the new dual dispersion system has better washing resistance and enhanced oil recovery in fossil hydrogen energy development. • A new DDS dual dispersion profile control system is proposed. • The physical property of DDS is tested. • The oil displacement performance of DDS is evaluated. • DDS can increase oil recovery significantly. [ABSTRACT FROM AUTHOR]

Abstract At present, the proportion of tight oil in non-renewable hydrogen energy is increasing. According to an initial exploration and attemptable practice on the exploration of tight oil, it is found that the cost can be controlled effectively and positive effects are achieved. But this technique cannot make sure the proppants filled uniformly in the long fracture. Several researches on the proppants migration experiment devices and factors influencing on proppant setting are reviewed and a new set of experimental device to simulate the laws of proppants setting in long fracture is developed. This device can simulate the main factors influencing proppants setting performance. It analyzes several factors such as wall filtration, construction displacement, sand concentration, proppant size and density, viscosity of fracturing fluid is used to rank the influencing degree of every factor. Considering the effects of mutual interference between proppants, width of fracture, rough fracture surface and fracture surface filtration during the proppants setting progress, the mathematical model of proppant setting is modified by adding sand concentration correction factor, wall effect correction factor and filtration correction factor. The experimental data verify the accuracy of the settlement model is established using the data getting from experiment. Highlights • Simulated the factors influencing proppant placement, including wall filtration. • The mathematical model of proppant placement is modified by adding filtration correction factor. • The influence of different factors on proppant placement is quantitatively analyzed. [ABSTRACT FROM AUTHOR]