Abstract
In this paper, a three-dimensional spatial-temporal decomposition modelling method is proposed to build the alkali-surfactant-polymer (ASP) flooding model, in which a new dynamic recurrent wavelet neural network (DRWNN) is presented to identify the temporal coefficients. At first, the detailed mathematical model of ASP flooding is described which is a complex distributed parameter system. Then a three-dimensional spatial-temporal modelling method is inferred based on Karhunen-Loeve (K-L) decomposition to decompose the water saturation of reservoir into a series of spatial basis functions and corresponding temporal coefficients. Furthermore, the recurrent wavelet neural network is used to acquire the identification model, in which the injection concentrations of ASP flooding and temporal coefficients are taken as the input and output information. In order to improve the capability of dynamic modelling, DRWNN is proposed through adding feedback layers and setting the different weights with time to achieve dynamic memory of the past information. Considering the gradient descent method for the neural networks training easily leads to local minimum and slow convergence speed, the spectral conjugate gradient method is introduced to optimize the weights of DRWNN. At last, DRWNN is used to build the relation between the moisture content of production wells and the water saturation of the corresponding grids. Thus, the final approximate model of ASP flooding is finished. The accuracy is proved by model with four injection wells and nine production wells through data from the mechanism model.
Highlights
With the old oil fields entering the later period of development, moisture content of reservoir is increasing, and the oil production is reducing [1]
The author gave the proof about global convergence and fast descent. On account of these advantages, the spectral NPRP (SNPRP) conjugate gradient method is adopted to train the weights of dynamic recurrent wavelet neural network (DRWNN)
In order to verify the modelling ability of the proposed DRWNN, A single input single output dynamical nonlinear system is used for the testing
Summary
With the old oil fields entering the later period of development, moisture content of reservoir is increasing, and the oil production is reducing [1]. How to update the technical means to ensure oil recovery is one of the most important measures to stabilize oil production. ASP flooding is an important tertiary oil recovery technique which is widely studied [2]. It can enhance the oil production by use of the interaction among alkali, surfactant and polymer to improve the physicochemical property of reservoir. There is lack of a uniform mathematical model description because of the uncertainty of alkali reaction. It is important to build an accurate and to be applied model in the research of ASP flooding
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