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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]