Stratified Water Injection Effect Evaluation and Field Practice Based on Single Sand Body Understanding

In recent years, fine stratified water injection work has been carried out in Changqing oilfield. The number of injection wells has exceeded 10,000, and the injection rate is nearly 50%. Fine stratified water injection technology has become one of the key technologies for sustainable and stable production in Changqing. However, due to the influence of monitoring means and injection structure, it is difficult to evaluate the effect of stratified injection. According to the characteristics of Changqing low permeability reservoir, 12 evaluation parameters were selected based on the single sand body characterization results and understanding, combined with numerical simulation. By using grey relational analysis method, the quantitative evaluation criteria of fine stratified water injection in low permeability reservoir are established by calculating the correlation degree and weight coefficient, determining the classification limit of quantitative parameters and determining the evaluation system. The effect of fractional injection is divided into three levels, and the effect of fine layer injection is analyzed from macroscopic and microscopic aspects. The results show that stratified water injection can better improve the longitudinal water absorption, improve the water driving degree, and achieve the purpose of decreasing decline and enhancing recovery.