Deformation Of Ductile Cuttings From Sandstones In Compaction Process And Experimental Study Of Influence On Porosity

Ever since the concept of diagenesis was put forward, greatprogress has been made in relevant research, especially in the oil and gasexploration field (Liu&Zhang,1992; Feng,1993; Fu,1998; Wang et al.,2000; Zhao,2001).Compaction is an important part of diagenesis, having agreat impact on the pore evolution and reservoir physical properties (Fisheret al.,1999; Kuang et al.,2002; Chen et al.,2002; Zhang et al.,2003).Numerous studies show that compaction can have a significant impact onpore structure and distribution of sandstones, resulting in a substantialreduction in pore spaceHowever, in the research of reservoir diagenesis by scholars in the lastyears, the influence of compaction on deformation characteristics ofsandstones and porosity has been more emphasized on some brief,qualitative description and analysis. The research of simulation experiment of compaction was not emphasized. To further explore the deformationcharacteristics of the plastic cuttings in compaction process and its effect onporosity, we take Bohai Basin as a target area, the geological background ofthe basin as a reference for the relevant simulation.Bohai Bay Basin is continental fault basin in Eastern China,basin-wideproven reserves of crude oil has more than100x108t,Bohai bay basin isfound the most crude oil at present in China which has been nearly50yearsof Exploration history.Bohai Sea Paleogene depression developed manyhydrocarbon-rich depression which is low level of exploration andexploration potential is tremendous.According to thin section identification,we can determine the basinreservoir rock types are mainly feldspathic lithic sandstone,lithicarkose,arkose and a small number of lithic sandstone.Granularity is givenpriority to with fine grain, grain and coarse grain in the second and moderatesorted.As the background for reference,we design and implementation of therelated experiments.The experimental sample select river sand which contains a certainamount of ductile cuttings, the content ratio and particle size are refered torelated parameters of the reservoir in bohai sea basin, and completed therelated experiment with using “experimental system of triaxial rockdeformation”.The design indexes are as follows: simulated depth0-4000m, interval depth500m, and pressure range0-120MPa at interval of1.5MPa.The experimental results show that the porosity decreases as buried depthincreases, and there is a negative relationship between them. The amount ofcompression was mainly obtained by porosity reduction and cuttingdeformation. Deformation of ductile cuttings is mainly ductile deformation;and deformation of crystal fragments is mainly expressed as brittle fracture,resulting in decrease of particle size. The research is of certain value for theexploration and development of oil and gas.