Research and Exploration of Multi-round Energy Boosting Water Injection Technology

In response to the problem of low production and low energy in the late production period of volume fracturing transformation of horizontal wells in tight oil reservoirs, energy-enhancing water injection and throughput technology is proposed. In order to solve the problems of poor throughput effect, rapid production decline and limited recovery improvement, the study on the mechanism of oil enhancement and the influence factors of multi-round energy-enhanced water injection and throughput were carried out. Based on a tight oil block in an oil field, we analyzed the pore structure characteristics of the reservoir using high-pressure mercury pressure technology and nuclear magnetic resonance technology. Comparative experiments were conducted to analyze the elastic and percolation-displacement mechanisms in the throughput process. The effect of each factor on the recovery rate was investigated at core scale and single well scale through multiple rounds of indoor experiments and numerical simulations of energy-enhanced water injection and throughput. The results show that the target block is a dense mesoporous reservoir, and the 1–3 rounds are highly efficient oil recovery stages, with elastic drive contributing the main recovery. The recovery rate shows a parabolic relationship with the injection pressure, which increases and then decreases; with the increase of the transfer pressure, the recovery rate increases and then decreases; in a certain range with the increase of the fracture density, the recovery rate gradually increases. Numerical simulations of single-well-scale horizontal fractured well injection and throughput concluded that the fracture network density is the key parameter to improve the recovery of low-permeability reservoirs, and injection pressure and stewing time are the main parameters affecting the recovery rate. The paper further analyzes the oil enhancement mechanism of multi-round energy-enhancing water injection and throughput, clarifies its main control factors, and provides implications for the subsequent program optimization..