The challenges posed by elevated rock hardness, deficient drillability, excessive friction torque, and significant underpressure in extended−reach horizontal wells are the primary factors that contribute to low ROP (Rate of Penetration) and limited horizontal reach during the drilling operation. Reducing drag and friction is one of the primary methods of addressing the aforementioned challenges. To augment the pulse output characteristics of the oscillating jet and bolster the energy of the hydrodynamic impact load, we developed and designed a multi−source impact oscillation speed−increasing tool coupled with blade rotation disturbance and multi−order oscillation cavity self−excitation. We utilized fluid dynamics software to model and conduct numerical analysis on the multi−source pulsed jet generator. Furthermore, we constructed a prototype and subjected it to testing. This paper examines the impact of dimensionless structural parameters on the pressure output characteristics of the multi−source pulse−jet generator. Specifically, we used three dimensionless quantities (cavity length ratios, cavity diameter ratios, and inner wall collision angle ratios) to study this effect. The findings indicate that the multi−source impact oscillation speed−increasing tool is capable of augmenting the pulse oscillation amplitude, and the frequency of pulse oscillation can be adjusted within the range of 5 Hz to 15 Hz. During the study, we determined that the optimal oscillation output characteristics can be achieved when the cavity diameter ratio is 0.8, the cavity length ratio is 1.0, and the inner wall collision angle ratio is 1.5. These findings present a novel approach for the development of downhole hydraulic impact oscillation speed−increasing tools.

Gravel particles are widely developed and randomly distributed in deep reservoirs of the Tarim Oilfield, western China. The mechanical behavior of conglomerate, the main component of the gravel layer, under varying confining pressure and different gravel content, remains poorly understood, especially in terms of the microscopic aspect, which limits the analysis of the variation patterns of underground engineering parameters. This study conducts triaxial compression tests on outcrop specimens from various stress levels to analyze the effects of stress state and stress differences on the mechanical parameters and failure modes. After that, a kind of numerical modeling method based on the discrete element method (DEM) is proposed, which considers the random distribution of gravel particles, to study the microscopic observation of mechanical characteristics and crack propagation of conglomerate under different stress state conditions. The experimental and numerical simulation results indicate that the horizontal strain before failure remains nearly constant in the axial direction while increasing linearly for the horizontal stress. And, it was observed that the volumetric failure was accompanied by gravel fragmentation, sliding, and falling. Numerical simulations reveal that cementation strength and gravel content significantly influence mechanical properties and failure modes, which are the main factors. This study provides some useful references for further understanding of the mechanical behavior and failure mechanisms of rocks in the gravel layer, in particular, the numerical modeling method for heterogeneous materials.