Study On Pore Structure Of Tight Glutenite Reservoirs

Paper whose research object is the sandy conglomerate reservoir in Mahu depression has mainly carried out two parts of research contents:one is the regular pore structure characterization, another is the pore structure characterization based on image processing. Aimed at the pore structure characteristics of sandy conglomerate reservoir, lots of technical means have been combinized such as the casting thin sections, the high-pressure mercury injection, the nuclear magnetic resonance (NMR) and image processing, to analyze the micro pore and pore throat characteristics of reservoir qualitatively and quantitatively, to establish a classification method of reservoir pore structure by means of routine analysis. Based on the convenience and intuition of the image, pore geometry characteristics have been analyzed. Then combined with the nearest neighborhood method, the spatial distribution of pores in the two-dimensional plane has been quantitatively analyzed. Finally, using the nuclear magnetic resonance (NMR) and the image parameters, the relationship between the two-dimension image information and nuclear magnetic information was studied.Research has showed that:(1) The four main rock types of the research area are intermediate fine sand, grit sand, fine conglomerate and fine-pebbly conglomerate. The average porosity of the reservoir is 9.17% and the average permeability is 3.7867×10-3?m2, which belongs to typical tight sandy conglomerate reservoir. The reservoir space is mainly intergranular pore and dissolved intragranular pore. (3) Due to the convenience and the intuition of the observation in the section, this research focus on using image processing technology to furtherly dig its quantitative information. The analysis of 20 samples of casting thin sections photos shows that the overall reservoir has poor areal porosity. In order to better characterize the 2D pore structure in microscropy, the five samples have been selected for image processing which have good areal porosity relatively. According to the 2D geometric feature analysis of five samples finds that:the shape of the intragranular pore tended to be more circular cross section, the shape of the intergranular pore tended to be more complex. (4) Studying the relationship between the reservoir pore type and the 2D space distribution, the proportion of two kinds of pore directly affects the overall distribution of pore system. The higher proportion rate of the intergranular pore, the more randomly pores distributed. And the positive relationship between the areal porosity and the nearest neighbor coefficient NNA of intergranular pore shows that the compaction maked only rigid particles pore preserved aroundly, which leads intergranular pore distribution becoming more cluster. Space distribution coefficient of intragranular and intergranular pore shows that intergranular pore distribution status directly affects the distribution of dissolved intragranular pore in the study area. The correlation study between the physical properties and 2D pore information shows the results. They have good linear relationship including porosity and 2D cross-sectional area, shape factor and NNA. Permeability and 2D pore information have the good exponential relationship. (5) By analyzing the areal porosity and nuclear magnetic T2 spectrum distribution characteristic of long relaxation part, we finds that they have good correlation. The relationship established between different long relaxation rate of parts and areal porosity shows that section image can well reflect the macropores information. The relationship studied between 2D pore information and the T2 relaxation time shows that different radius and types of porosity have the same T2 relaxation time. Not only shape and area effected, but also affected by the distribution of the pore space. On this basis, the new formula between T? relaxation time and the pore radius is deduced in this study. The coefficients of a and b, shape factor SF, and spatial distribution coefficient NNA have a good power function relationship.This paper routinely studied the tight sandy conglomerate reservoir in the reseach area. Based on the digital image processing, not only the pore space distribution has be innovatively studied in the section, but also new thinking about the transforming method on T2 converting to radius of pores was proposed through combining other 2D information from image?...