Analysis on Seepage Theory and Dynamic Characteristics of Comingle in Multi-layered Tight Reservoirs

By coupling formation percolation theory, the dropdown well test theory and wellbore pipe flow equation, the present paper investigated production performance law of multi-layer reservoirs without the interlayer crossflow. In addition, under the production system of constant rate, bottom hole pressure formulas were derived through dimensionless transform, laplace transform and numerical inversion with the method of stehfest. It has been found that interlayer spacing was one of the main factors which had a significant impact on interlayer interference. Under the production system of constant bottom-hole pressure, the production of each layer and the contribution rate of well yield for each layer were derived. The main results demonstrate that the irrational interlayer spacing will exacerbate the flow resistance of the fluid in the tubing, increasing bottom-hole pressure drawdown loss. From the dropdown well test curve, it can be seen that the dimensionless pressure curve will rise and dimensionless pressure derivative curve will become flattened. The dimensionless permeability, skin factor, dimensionless storativity ratio and dimensionless oil displacement radius have significant impacts on the contribution rate of yield for each layer. During early and middle stages of development, contribution rate of yield is affected by the skin factor and dimensionless permeability, however, during the late stage, it is mainly affected by the dimensionless radius and dimensionless storativity.