Prediction Of Gas-bearing Property Of Limestone Of Taiyuan Formation In Eastern Ordos Basin In Zhou 3 Well Area

The Paleozoic in Ordos platform is dominated by epicontinental sea and marine-continental excessive facies deposits.Carbonate rocks are generally developed in Cambrian,Ordovician and lower Permian Taiyuan Formation.Marine carbonate rocks often have the characteristics of old development period,deep burial and strong diagenesis transformation in the late stage,which makes the geological conditions of reservoir formation complicated.Drilling test data show that the Upper Paleozoic Permian Taiyuan Formation is an important gas producing layer,and has good exploration prospects.In this paper,the existing geological,logging and seismic data are used to carry out and improve the research on carbonate reservoir evaluation and gas-bearing prediction technology,so as to provide theoretical help for further exploration and development.In this thesis the Taiyuan Formation limestone reservoir in Well Block Zhou 3 in the eastern Ordos Basin is taken as the research object.The geological conditions of Taiyuan Formation limestone reservoir formation in the study area are studied by using core observation,logging,seismic data,qualitative analysis to quantitative prediction analysis,combined with the principles and methods of sedimentology and other disciplines.Based on the characteristics of different lithology and fluid logging data,the seismic attributes are extracted,and the lithology and fluid identification are studied by using the forward modeling of geological model and the inversion of seismic attributes.Gas bearing property of Taiyuan Formation limestone was detected by fluid factor.According to the research results,the evaluation index of favorable areas is determined,and the comprehensive evaluation of favorable areas is carried out.The volume method–probability method is used to evaluate the potential of natural gas resources in this area.The main achievements and understandings are as follows:(1)Taiyuan Formation limestone is characterized by ultra-low porosity and permeability.The early tectonism significantly improved the permeability of the reservoir in the study area,and the structural microfracture-dissolution fracture was the main reservoir space and migration channel.According to the different types of formation,the reservoir space is divided into three categories,and the three types of reservoir space overlap each other.(2)According to the different contact lithology between the top and bottom of limestone,the gas generation,storage and cover combination of limestone in the source can be divided into three types.Among them,the gas bearing capacity of type I bottom coal slime generation,medium ash storage and top mud seal is the best.(3)Based on logging,rock physical data and forward simulation results,it shows that the seismic response characteristics of different thickness and lithology are significantly different.Combined with seismic superposition section,wave impedance inversion section and fluid activity detection section,the interlayer fluid analysis was carried out in Well Block Zhou 3.The results show that the Taiyuan Formation limestone meets the gas-bearing conditions.(4)The volume method-probability method was used to evaluate the potential of natural gas resources in the study area.The natural gas resources of Taiyuan Formation limestone in eastern Ordos Basin are 308.5×10~8m~3.Considering lithology combination,palaeogeomorphology,tectonic shape,curvature and gas-bearing evaluation criteria,three favorable target areas are further divided,and the gas-bearing property of type I favorable area is the best.