Research On Well-logging Identification And Distribution Characteristics Of Elastic-plastic Compression Section And Burst Section Of Sand And Mudstone

In the Paleozoic strata and overlying Paleozoic strata on the e of Ordos Basin, the vertical and horizontal distribution of elastic-plastic section and burst section of sandstone and mudstone is a basic geological factor, which controls the area of natural gas reservoir and distribution. At present, research in this area is still very weak. This paper through observation of core and thin section, sandstone and mudstone interval transit time curve and logging identification of elastic-plastic compression section and fracture section of sandstone and mudstone conducted a preliminary study on Upper Paleozoic in Ordos Basin,and analyse the distribution, characteristics of elastic-plastic section and fracture section, made the following understanding:1. Logging identification of elastic-plastic compression stage of sandstone and mudstoneThe porosity of sediment in elastoplasticity compression section decreased slowly or even remains the same with the increase of buried depth in the process of sedimentation burial evolution.The acoustic time value of sandstone and mudstone is fitting as compaction curve,the response features of elastic-plastic compression stage on the curve increase with the depth, the acoustic time value slowly decreased or even remain the same.In general, in the stone of uneven mixed particle or pore is more developed, the elastic-plastic is more obviously.2. Logging identification of fracture section of sandstone and mudstoneThe vertical fractures generally exist in well developed rock surface, with tightly packed particles and relatively homogeneous structure. The conventional logging curve always performs that the compensated neutron value increases, while compensated density value decreases, at the same time, the change of acoustic time value is not obvious, There is a positive separation between deep and shallow dual lateral resistivity logging curves.The parallel plane fractures (Low angle oblique crack) generally exist in well developed rock surface with uneven structure and different lithology interfaces. The conventional logging curve usually performs that the acoustic time value is increasing, even appears cycle skip phenomena,with compensated neutron value increases,and compensated density value decreases.There is a bit negative separation or no obvious separation between deep and shallow dual lateral resistivity logging curves.3.Sand and mudstone elastic compression section and distribution characteristit of the fracture sectionThrough shanbei slope of ordos basin in274Wells of upper palaeozoic in the sand and mudstone compaction curves,the three porosity log curves and the deep and shallow dual lateral resistivity loging curve value range and statistics and comprehensive analysis of characteristics of the results found that elastic-plastic compression section mainly developed in the upper Shiqianfeng formation the lower Triassic strata and burst section mainly developed in the lower Shiqianfeng formation,shanxi formation and Taiyuan formation strata In the Paleozoic strata and overlying Paleozoic strata on the northern Shaanxi slope-of Ordos Basin.elastic-plastic compression section and burst section of sandstone and mudstone can.do the Horizontal comparison,found that they are widely distributed in northern shanxi slope of ordos basin tectonic belt.