Optimal Model Selection Based On Reserves Method

In recent years, with the development in oilfield approaching to later stage, exploration on oil and gas becomes more and more difficult, leading to high accuracy requirement for geological research. Therefore, It is more important to establish a relatively accurate geological model with geological thinking ability added in, we can study on reservoir quantitatively from three dimensional angle, finding the optimal model and guiding production in the late period. After implementation of ODP in study area, many problems appear:gas-oil interface of various wells are different. Variations in depth are nearly 4m. gas-oil interface cannot reach agreement, leading to misunderstanding of the size of gas cap gas. It Influences later reservoir development strategy formulation and optimization of working system. After the implementation of the ODP, drilling has been put into production and urgently needs to establish the geological model. Reservoir characterization and physical properties can be described truly in distribution in three-dimension respective. As is known to all, there is less wells and big study area in ocean areas, the size of the interlayer cannot control the reservoir for uncertainty is large. There is need to find suitable method to quantitatively characterize the uncertainty and select favor models with mathematical methods. Verifying models from the perspective of dynamic optimization models and the rationality of the reservoir properties for the subsequent reservoir numerical simulation parameters, determing reasonable production schemes and providing guidance on optimize the adjustment of oilfield production.This paper embarks from basic geological study, combing with specifics of work area with various disciplines integration with each other. Firstly, we should make full use of well logging, seismic information, core, drilling and so on other sources of scientific geological theory and research on it in-depth. Then, based on geological study in science,3 dimension visualization of geological model of work area can be established with application of the advanced geologic modeling software PETREL and various possibility changes can be simulated at the same time, in offshore oil field, the size of inter-face cannot be controlled with strong uncertainty. The method of experimental design is adopted. With some test instead of a comprehensive test, through the analysis of the part of the test results, the situation of comprehensive test can be understand with part of the test results. Lastly, the most likely model can be found by the method of probabilistic reserves queuing model and on the basis of the model coarsening through history matching reservoir numerical simulation method to check the model of optimization. The main results were as follows:(1) Reunderstanding the geology characteristics of the study area from the structural feature, stratigraphic correlation, characteristics of sedimentary facies and reservoir characteristics.(2) Studying the recognition method of gas-oil contact. Established the recognition method that combined the vertical well and horizontal well, and proposed the methods that recognize vertical Wells by using the method of reservoir resistivity composite, while adopt "the butterfly engraving method" and "intersection chart method" to identify horizontal well.(3) Review the geological data by the powerful visual function of Petrel software, and correct a variety of data error. Identified the plane and vertical relationship of faults, and make appropriate adjustment to establish the fault model which can accurately describe the actual fault forms of the field, can provide a good structure skeleton for facies and property modeling.(4) The difficult in the characterization of interlayer scale resulted in deviations in understanding the reservoir, make a lot of investigation and research on the interlayer from the proportion of interlayer, plane length of interlayer, length/width and the vertical thickness, nine sedimentary microfacies model is established under the constraint of the fine structure skeleton by the method of orthogonal experimental design, in order to portrays the shape of interlayer, the object-based simulation algorithm is employed here, the model established can reflect the distribution of sand body and interlayer.(5) Established 108 reservoir property models on the control of sedimentary microfacies by uniform experimental design method. On the basis of geological research, the lower limit of physical property is obtained by core analysis. Establish the NTG model, calculating reserves of 108 models, and fitting with the ODP reserves after the implementation of the drill, selected models through the ranking method which takes probabilistic reserves as ranking index. The error between the reserves calculated by the optimization geological model geological workers is smaller, which reflects the accuracy of geological model in some extent.(6) In addition, through the history matching method of reservoir numerical simulation to test the accuracy of the model.