Fracture Characteristics And Log Evaluation Of Volcanic Reservoirs In Deep Northern Songliao Basin

Volcanic formations are distributed diffusely in the deep part of northern Songliaobasin. Volcanic reservoirs are the important gas prospecting target of this area currently andin the future. They are the main objective formations for gas reserve. In the volcanic reservoirs fractures are existed extensively. The reservoirs type aredual-pore media, that is there are two type of pores, intergranular and fracture. Due to porestructure permeability is improved. A great production of gas can be achieved even thoughthe features of logs show that it is a tight formation. Therefore calculating fractureparameters of these formations is very important, which eventually will be basic data foreffective thickness and reserve. The paper describes the forming mechanism and distribution of volcanic reservoirs,discusses the reason of fractures, their geological feature and effecting factors of theirdistribution. The following aspects are also discussed in the paper: rock naming frommineral components, lithology determination from logs based on the chemistry analysis ofsamples and their log responses, setting mineral model for volume analysis, facturedeveloping extent by evaluating fractal dimension of logs, integrated formation evaluationby using SIMPLE( a system of igneous and metamorphic petrophysical log evaluation) 1. Research works fracture are existed in volcanic rocks. But the extent in different rocks is different.What is the reason? The status of volcanic formation evaluation shows that there are several 吉林大学硕士论文 作者:吴海波 105摘 要problems in this research area. There is no proper model, lack the proper parameters andfracture extent evaluation. There is no suitable saturation equation. This paper conducted systematically researches on the above problems of volcanicformation evaluation. The main research works include: 1). Discussion of log responses and effecting factors of fractured volcanic rocks; 2〕summary of log responses of various volcanic rocks; 3). methodology of identifying lithology automatically; 4).discrimination of fractured zone and evaluation of fracture intensity; 5). determination of petrophysical parameters; 6). software development. 2.Research achivments The fracture in volcanic formation of Sonliao basin are controlled by two factors:alternation and tectonic. The volcanic rock fractures can be classified into 5 types: open,shear, compress, open-shear and compress-shear, based on the forming mechanism offractures. The most important fracture group in the area is NNE with high angle, the othergroup is NNW and developed less than the former. Based on the analysis of geological and log features of several fractured volcanicreservoirs, the log regularity of different volcanic rocks is obtained. By usingcorrespondence analysis the relationship between different volcanic rocks is known, and themost important logs sensitive to lithology are picked out from all logs. The methods oflithology identification are studied: fuzzy cluster, principle component analysis (PCA). Thecoincidence is over 80%. Regards to the fractured zone identification and the evaluation of fracture intensity,deriving fractal dimension from logs shows that the more developed the fractures, the higherthe fractal dimension. In order to eliminate the effect of lithology and to keep a certainvertical resolution the fractal dimension is derived from the residual changes of MicroFocused Spherical Log(MSFL) after filtering. The fractal dimensions can indicate the 作者:吴海波 吉林大学硕士论文 106松辽盆地北部深层火山岩储层裂缝特征及测井评价fractured zones reliably. The results can be compared with fracture parameters from imagelogs. The rock matrix parameters are determined based on the core porosity...