The Study Of Dynamic Prediction Methods For Oilfield Development Programming In Ultra-High Water-Cut Stage

Accurately dynamic prediction of oilfield development and scientific oilfield development programming are the basis of the reasonably, efficiently and continually developing of the east oilfields of China, for they presently have generally entered ultra-high water-cut development stage. The exiting methods of oilfield development dynamic forecasting are the trend forecasting method of single variable development index and the prediction method of single variable development index based on affecting factors. However, each method has its limitations, which its applied scope, prediction conditions and complexity are all not the same in the different development stages. The prediction method based on the multi-input and multi-output development indexes and their factors still need to further study in theory and application. With the applicability analysis of the methods commonly used in oilfield development dynamic prediction, new dynamic prediction methods for development programming according with the law of dynamic change of oilfield development in ultra-high water-cut stage are established in this paper, these methods solve the theory and application problems which restrict the prediction method based on the multi-input and multi-output development indexes and their factors. The new methods include support vector machine forecasting, functional simulation prediction based on time-varying system, probability simulation forecasting, combination forecasting and intelligent forecasting. The first three methods utilize the functional simulation method to establish the input-output of development dynamic predication system and the relevant prediction model of development indexes essentially based on the functional simulation of oil and gas dynamic system and the oilfield development historical data. The prediction method of support vector machine forecast system is mainly focused on prediction problems with a small of samples; the functional simulation prediction with time-varying system is focused on multi-step prediction of time-varying system; the probability simulation forecasting is more focused on random uncertainty of system; the combination forecasting solves the problem of improving forecasting precision; the intelligent forecasting emphasizes particularly on selecting adaptively and independently the most appropriate prediction method.The experimental results of these new prediction methods show that oilfield development dynamic index prediction system in ultra-high water-cut oilfield conforms to reality, and the designing algorithms are correct and feasible. It enriches the theory and method of dynamic prediction of oilfield development, and provides the theoretical basis and important technique support with making and establishing the scientific schemes of development programming for ultra-high water-cut oilfield that dynamic prediction methods of ultra-high water-cut oilfield development programming which was suitable for the different oilfield being developed, the standards of selecting prediction index and its influence factor being determined and the studying method about the correlation between the oilfield development index and its influence factors be presented in this paper. Main topics involved in the thesis are as follows:(1) With development characteristics and facing problems of ultra-high water-cut oil reservoir, this paper analyzes the applicability of common methods used in dynamic prediction of oilfield development; Compares and evaluates the laws and limitations these methods followed, and then draws the conclusion that the existing common methods are not suitable for the dynamic prediction of ultra-high water-cut oilfield development programming; and points out its development trend.(2) Based on the theory and method with engineering and mathematics, the method of correlation analysis between development index and its influence factors of ultra-high water-cut oilfield is established. According to dynamic change law of ultra-high water-cut oilfield, the possible development indexes and their influence factors of different ultra-high water-cut oilfield are first determined by the theory of reservoir engineering and oilfield development etc. Then a correlation analysis of development indexes and their influence factors is made through using relational analysis. Or according to functional simulation of oil and gas dynamic prediction system, a correlation analysis of development indexes and their influence factors is made by using fuzzy correlation classifying method starting from historical data of development indexes and their influence factors. As a result, the criteria of selecting prediction index and its influence factors are determined, and the system of development indexes and their influence factors of the different oil reservoirs in ultra-high water-cut stage are established.(3) According to the problems of the less sample numbers of development indexes and their influence factors generally collected in ultra-high water-cut oilfield stage, local minimum point, over learning and under study with existing method, after this paper analyzed the prediction method of support vector machine by utilizing multi-objective optimization and studied the kernel function and parameter selection problem, it puts forward a method for selecting kernel function of single output and multiple output support vector regression machine by using feature analysis data mining method of development index time series analysis.(4) For the accuracy problem of multi-step prediction by using common prediction method or the poor effect of middle-long term prediction, a functional analogue method based on time-varying system with the time varying characteristic, parameter of prediction model changing with time and better effect to middle-long term prediction is established by integrating the high fitting accuracy and close relation between prediction index and its influence factors of neural network simulation with the advantage of differential simulation prediction paying attention to the change trend of prediction indexes themselves.(5) After studying the principle and method of combination forecasting for solving the problems of information inadequacy of single prediction method and its limitation, this paper presents an improved method to determine the weight of combination forecasting method. Though studying the principle and method of intelligent prediction method, the intelligent forecasting method about the oilfield development index system is established to realize automatic prediction of development index.(6) Considering the more serious stochastic uncertainty of geological factors and man-made factors affecting oilfield development in ultra-high water-cut stage and the insufficiencies without studying randomness and possibility of all existing development index prediction methods, the uncertainty prediction method and model of oilfield development index system are explored theoretically and practically in this paper.(7) Study on application of forecasting method. The algorithm and the application program for new methods of dynamic prediction of ultra-high water-cut oilfield development programming are designed and developed. The development index prediction case of one oilfield of china in ultra-high water-cut stage is studied with the presented method in this paper. The prediction result shows that dynamic prediction method of ultra-high water-cut oilfield development programming established in this thesis has bigger theoretical and practical value, and it is worth of expanding range of application.