Fractal Study Of Fractures In Xinglongtai Buried Hill Of Liaohe Oilfield

In the last century,French scientist and mathematician Mandelbrot,when studying the length of the coastline,found that the dimension can be not an integer,but a fraction,and then put forward the concept of fractal.Many complex problems in nature,such as the study of tectonic fractures in geology,the length of rivers and the biological growth model,can be quantitatively studied by fractal theory.The oil-bearing reservoirs in Xinglongtai buried hill have complex lithology,mainly consisting of a set of biotite gneiss,migmatite and diorite porphyrite dikes with relatively developed fissures.The oil-bearing bottom boundary is deep and the reservoirs are concentrated,but it is difficult to study the fracture.Reasonable and efficient development of fractured reservoirs is the main problem at home and abroad,and the distribution law of fractures is the main factor restricting the research.With the maturity and application of fractal theory in the 1970 s,great progress has been made in the study of nonlinear complex science.Previous studies have demonstrated that the structural fissures of Xinglongtai buried hill conform to the non-linear law,and can be studied by fractal method.This paper demonstrates its feasibility again through fractal studies of different scales.Due to the different development of fissures in different lithologies,the fractal study of biotite plagioclase gneiss,magmatic intrusive body and migmatite in Xing 7 borehole is carried out.The fractal dimension and correlation coefficient are calculated by using box method and covering on the scale of 2mm,4mm,5mm,8mm,10 mm,16mm and 20 mm.The fractal dimension of biotite plagioclase gneiss is 1.0778,R2 = 0.9997;the fractal dimension of migmatite is 0.9824,R2 = 0.999;the fractal dimension of diorite porphyry is 1.1965,R2 = 0.9894.The square of correlation coefficient is close to 1,which generally conforms to the fractal characteristics.Judging from the development of fractures,the biotite plagioclase gneiss has relatively developed fractures and larger fractal dimension.This proves that fractal dimension can also quantitatively describe the development of fracture On the regional scale,the regional tectonic maps of Xinglongtai buried hills are fractally studied.Fractal dimension is calculated on the scales of 0.2 km,0.4 km,0.5 km,0.8 km,1 km,1.6 km and 2 km,and the fractal dimension is 1.0476,R2=0.9949.The results are consistent with the fractal study of fracture at borehole scale.Fractal analysis of biotite plagioclase gneiss,diorite porphyrite,migmatite and migmatite was carried out at 0.002 mm,0.004 mm,0.005 mm,0.008 mm,0.010 mm,0.016 mm and 0.020 mm microscales under 25-fold microscope.The overall results are consistent with those obtained by regional and borehole drilling.Through the above statistical fractal study,it is found that the fractal dimension of buried hill fractures is between 0.96 and 1.3,R2 s are above 0.99,and the analytical characteristics are obvious.Fractal dimension can reflect the degree of fracture development.The larger the fractal dimension value is,the more developed the fracture is.Fractal study on oil production of lithologic reservoirs: reservoirs between 0.97 and 0.99 have better oil production;reservoirs between 0.99 and 1.01 have medium oil production,and reservoirs above 1.01 have poorer oil production than the former two.