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New Method Research For Low Porosity And Low Permeability Gas Reservoir Logging

Posted on:2013-04-19Degree:MasterType:Thesis
Country:ChinaCandidate:L M QinFull Text:PDF
GTID:2230330374476775Subject:Earth Exploration and Information Technology
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As the thorough degree of the petroleum exploration and development, the exploration and development of low permeability and low porosity sandstone reservoir is more and more attention; But the logging evaluation of low permeability and low porosity reservoirs is always difficult of reservoir evaluation. Reservoir evaluation and description is one of the most critical and crucial technology problem. Low permeability and low porosity reservoirs and other reservoirs have a very big difference in the reservoir characteristics, the characteristics of low permeability and low porosity make the reservoir fluid on the contribution of the logging response weakening in the very great degree, but also on the other logging environment effects, such as wellbore factors, make part of logging information can’t reflect actually the information of formation, so it became more difficult for log fluid of low permeability and low porosity reservoir to identify and evaluate.L oilfield is the biggest oil field at present in our country, the characteristics of low permeability and low porosity have the obvious differences in high permeability and porosity logging evaluation of other areas in the logging evaluation of oil and gas. Neopaleozoic reservoir of L oilfield forms in the late carboniferous-formation stage of Intracratonic basin in the Middle Triassic, the migration and cluster of oil field happened in Zhongshan movement period, the second migration completed in the Himalayan movement. Containing gas formation located mainly in the box8section of Shihezi group in Permian Systemand and mountain1section of Shanxi group, it is effected by the large rivers and delta sand body area of nearly north-south distribution, gas is compounded by more than single sand body of lateral distribution, which belongs to the lithologic trap gas reservoir.It is always difficult to research how to identify and evaluate the gas which has the characteristic of the low holes, low permeability, low production, low abundance and microcrack effectively and accurately in the exploration and development of L oil field. The theme of this paper is looking for a simple and effective new methods to evaluate the logging evaluation for low permeability and low porosity reservoir through the study of low permeability and low porosity oil field in L oilfield area, so that it can give the help to the exploration and development of low permeability and low porosity gas reservoir area.This paper mainly makes full use of logging data of L oilfield area to try all kinds of new methods in order to achieve good results in the lithological identification, gas identification and the determination of permeability of the low permeability and low porosity reservoir during the study of new methods for gas logging evaluation of low permeability and low porosity reservoirs.In the process of lithological identification of low porosity and permeability reservoir, there are mainly three methods which are conventional crossplot,high-dimensional samples pole descent method and pattern recognition,and sum up the three lithological identification methods for comparison. Conventional crossplot method to identify lithology is more intuitive, but because of the more logging response characteristics, it is more loaded down with trivial details in pairwise intersection of logging response characteristics,while its errors are large; The high-dimensional samples pole descent method is more convenient by running relevant program to map multiple logging response characteristics to one-dimensional, two-dimensional or three-dimensional space; To pattern recognition method, first of all extract logging response characteristics combination of the sample by the optimum search algorithm, and then use Bayes discriminance for decision of lithological has achieved good results in lithology recognition, but there is also the problem of determination of prior probability. In the process of lithologic identification, these three methods have their advantages and disadvantages, so we should apply these three methods separately basing on different layers, and choose the most effective way to identify each layer when recognizing low-porosity and low-permeability gas reservoir lithology.In the gas reservoirs identification process of low porosity and permeability gas reservoir, this paper mainly exerts dual-porosity overlay method to recognize gas reservoir qualificatively, natural gas notation qualificatively recognizing gas reservoir, and layer apparent matrix density qualitative identification of gas reservoir, which dual-porosity overlay method and natural gas notation show the effect more obviously and locate gas reservoir layer more accurately during the gas reservoirs identification process. It also has achieved good results by the combination of optimum search algorithm and support vector machine method in judging reservoir capacity.In the determine process of low porosity and permeability reservoir’s permeability, main utilize porosity-permeability relationship pattern, principal component analysis descent and the multiple linear fitting to determine penetration rate pattern; due to the complex regional geological relationship of low porosity and permeability reservoir, it is hard to reach ideal accuracy by using porosity-permeability relationship in entire region to establish penetration rate model directly, so first analyze permeability on reservoir interval, after descenting reservoir interval’s logging response characteristics by main components analysis, use multiple linear to fit penetration rate, like this, it will have a higher accuracy.
Keywords/Search Tags:Low porosity and low permeability, lithologic identification, patternrecognition, permeability
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