A PRODUCTION SPLITTING MODEL OF HETEROGENEOUS MULTI-LAYERED RESERVOIRS WITH COMMINGLED PRODUCTION

Abstract

Production splitting is the basis for a proper understanding of the development effect of reservoirs when multiple layers are commingled to produce, and it is a difficult part of the development evaluation of this type of reservoir. Reservoirs with multiple layers are usually developed through commingled production. However, due to interlayer interference, the total output of commingled production is lower than the sum of individual production of each subordinate layer. It's significant to clarify the interlayer interference mechanism during layers with commingled production, establish an accurate splitting model of the production from subordinate layers, split the commingled production into each subordinate layer, and effectively understand the production level and remaining potential of the subordinate layers during commingled production. It is expected to develop a theoretical basis for the rational and effective development of multi-layered commingled production reservoirs. In this paper, a combination of multi-tube parallel displacement experiments and numerical simulations of a multi-layered reservoir with commingled production is used to analyze the influence of factors such as permeability ratio, production pressure difference, and crude oil viscosity on the interlayer interference mechanism. According to the research results, the interference coefficient is firstly introduced on the basis of the theoretical production formula of seepage flow. The change rate of the oil production splitting coefficient at the stage when the water cut is more than 80% is also proposed, and the production splitting model of subordinate layers in heterogeneous reservoirs is established, considering multiple factors. Taking multi-layered Reservoir A with commingled production as an example, this model is used to split the production of commingled wells. Results show that interlayer interference can be reduced by decreasing the permeability ratio and high permeability laminar fluidity, and increasing the production pressure difference. When the water content is greater than 80%, the oil production segmentation coefficient of the layers with high permeability decreases sharply with the increase of the water content. For the low-permeable layer, the situation is just the opposite. At the same time, based on the study of the interlayer interference mechanism coupled with the oil well radial flow production formula, the interference coefficient and the oil production segmentation coefficient change ratio are introduced. The findings of this study can help develop a more accurate model for production of subordinate layers in heterogeneous multi-layered reservoirs. The established splitting model is carried out using the data from two wells and four subordinate layers in Reservoir A, indicating that the accuracy of the proposed model is close to 90%.