Self-degradable magnesium alloy-based temporary plugging ball for fracturing in deep reservoir

Abstract

With the exploration and development of deep-buried reservoirs in China, the existing techniques are struggling to meet the demand for deep fracturing. It is of great significance to develop a new type of high-temperature and high-salinity resistant temporary plugging material for efficient transformation of the reservoir, enhancing conductivity, and increasing the cumulative oil and gas production. Metal-based temporary plugging balls (TPBs) generally have good temperature and pressure resistance, but at the same time face the challenge of long degradation time. In this research, a kind of fast degrading temporary plugging ball (FD-TPB) was prepared using the stir casting method, which can maintain high-strength mechanical properties while forming low corrosion potential and exhibiting excellent degradation performance. The experimental results show that the density of FD-TPB is 1.75 g·cm^–3, and the settling velocity in fracturing fluid is 7.01 cm·min^–1. Vickers hardness is 46.38 HV at room temperature, compressive strength could reach 180 MPa at 210℃. The simulated plugging and diverting fracturing experiments show that it can effectively carry 49.17 MPa pressure under the temperature of 180℃, complete the operation and successfully create fractures in the reformed core. FD-TPB has a self-corrosion potential of –1.70 V and a self-corrosion current density of 3.15 × 10⁻⁵ A·cm⁻². At reservoir conditions of 210℃ and 22 × 10⁴ mg·L^–1 salinity formation water, the weight loss of FD-TPB can reach 90.1 % within 100 h. The mechanism of Fe nanoparticles enhancing degradation was proposed based on the morphological changes during degradation and microstructure of the materials. The successful development of FD-TPB provides a new technical solution for the efficient exploitation of deep oil and gas resources, potentially enhancing reservoir stimulation effects, and increasing cumulative oil and gas production.