Reservior Evaluation Of The First Member Of Xiashihezi Formation In Daniudi Gas Field D47-D70 Well Areas

Daniudi gas field D47-D70 well areas is located in the northeast of the gas field and has a control area of about 500km~2.The first member of Xiashihezi Formation is one of the main gas-bearing layers in the study area,and is mainly a tight reservoir of braided fluvial facies that has low porosity?permeability and strong heterogeneity.The study in reservoir characteristics and its influencing factors,the evaluation of reservoirs are relatively low.Aiming at the current problems in the study area,through the comprehensive analysis of drilling,logging and earthquakes,and in accordance with the characteristics of sequence development,a high-accuracy isochronal stratigraphic framework of the study area was established.The sedimentary microfacies type,spatial distribution,evolution and patterns of sedimentary microfacies were studied by using the theory of sedimentary system analysis.Combined with analysis and test data,and thin section observations,the characteristics of the reservoir were studied.Then,choose the characteristic parameters,the evaluation of reservoirs and the prediction of the favorable areas are performed using a combination of qualitative and quantitative methods,in order to provide some basis for further exploration in the study area.Through the careful observation of cores in the core wells,combined with logging curve characteristics,seismic data,etc.,based on the principle of“control by marked bed,cycle correlation,and hierarchical control”,combining cycle-thickness contrast with high-resolution sequence stratigraphy,the first member of Xiashihezi Formation in the study area was divided into three groups:H1-3 sand group,H1-2 sand group,and H1-1 sand group.According to the analysis of the RMS attributes plane distribution map?sand thickness plane distribution map?sand ground ratio plane distribution map,based on the comprehensive analysis of regional sedimentary background,the provenance of the first member of Xiashihezi Formation mainly originates from the northeast direction in the study area.The sedimentary facies are mainly braided fluvial facies,including channel lag deposit,channel sand body,channel bar,overfall sand body,interdistributary bay sedimentary microfacies.The study found that the first member of the Xiashihezi Formation is mainly lithic sandstone and feldspar lithic sandstone.Sandstone is low in compositional maturity and medium-good in textural maturity.Primary intergranular pore is a bit less in the study area.The main reservoir space is secondary pores.The most important of these is intergranular dissolved pore.Reservoir pore structure is complex and the seepage ability is poor.Porosity is mainly low porosity-ultra low porosity,and permeability is mainly low permeability-ultra low permeability.The first member of the Xiashihezi Formation has undergone various types of diagenesis.The early compaction and the cementation of various cement types have greatly reduced the porosity,dissolution has great improvement on reservoir properties.Through the study of the diagenesis stage and evolution,it is believed that the reservoir sandstone of the first member of the Xiashihezi Formation is in the middle diagenetic phase A period as a whole.Based on the analysis of the lithology,physical properties,and pore structure characteristics of reservoirs in the study area,select parameters to conduct a evaluation of the reservoir which is divided into four classes.The first member of the Xiashihezi Formation is dominated by???type reservoir,and the I type reservoir is the least.