| The Sanpu Depression is located in the northern part of the Hami Basin,and the Triassic Haojiagou Formation is the main target of oil and gas exploration and development.The reservoir quality of the Haojiagou Formation is poor overall,it is the type of tight reservoirs.Due to the large area in the northeastern part of Sanpu Depression,the drilling wells are sparse and unevenly distributed,the characteristics of tight reservoirs are not fully understood,and the development pattern of reservoir parameters is not well understood.This paper had made full use of core experimental analysis data,geological Information,logging and seismic data to research the distribution characteristics of sedimentary facies,tight sandstone reservoir characteristics,reservoir parameters calculation,3D geological modeling and the favorable reservoir prediction of the Haojiagou Formation.The main results and understanding are as follows:(1)The sedimentary facies types and distribution of the Haojiagou Formation in the northeast part of the Sanpu Depression have been clarified.The Haojiagou Formation mainly develops braided river delta frontal deposits,a small amount of fan delta frontal deposits are developed in the first member of Haojiagou formation.The sedimentary micro-facies is dominated by underwater distributary main channel,underwater distributary sub-channel and underwater distributary inter-channel,with the largest area developed underwater distributary inter-channel,and the development of mouth bar and sheet sand is not obvious.The braided river delta frontal deposits are mainly distributed in the middle and east of the study area,near the source area,the shore shallow lake sedimentary facies is mainly distributed in the western part of the study area.(2)The microscopic characteristics and causes of tight of the Haojiagou Formation reservoir are illustrated.The rock mineral composition of the Haojiagou Formation is mainly quartz,feldspar and rock chip,with high overall gap-filling content and small rock size class.The pore type is mainly residual intergranular pore,with few secondary dissolution pore and poorly developed pore throat structure,which can be divided into Type I micro fine throat--low displacement pressure type pore throat structure and Type II micro throat-middle displacement pressure type pore throat structure.The particle contact mode is mainly point-line contact,and the clastic structure is highly mature.The strong compaction is obvious in the diagenetic characteristics and weak cementation performance,and strong compaction is the main factor of tight reservoir.(3)The correlation between seismic attributes and reservoir parameters of the Haojiagou Formation is established,and the reservoir parameters are accurately calculated.The RMS seismic attributes correlate best with the ratio of sand parameters,and the overall correlation coefficient R=0.79.The correlation coefficients of RMS seismic attributes with the first,second and third member of the Haojiagou Formation are 0.77,0.79,and 0.79,respectively.In the correlation of lithology and physical property parameters,fine sandstone has the best porosity and permeability and the most content.Among electrical and physical property parameters,AC has the best correlation with porosity.In the correlation between physical parameters,porosity and permeability are exponentially correlated.Among the correlation between lithology and oil-bearing parameters,the oil-bearing property of fine sandstone is the most obvious and the number is the most.(4)The structure model,sedimentary facies model and reservoir attribute model of Haojiagou Formation are established to improve the accuracy of the model.The structural model constrained by seismic data is in accordance with the spatial distribution characteristics and geological recognition rules of Haojiagou Formation reservoir in northeast Sanpu Depression,the sedimentary facies model is consistent with the planar distribution of sedimentary facies,and the result of reservoir attribute parameter model constrained by sedimentary facies model is better.The porosity and permeability parameters show a decreasing trend between underwater distributary main channel and underwater distributary sub-channel in the attribute model,and the effect of sedimentary facies constraint is good.The test of rarefying wells and the consistency comparison of probability parameter distribution test model effect is good and the model accuracy is high.(5)A comprehensive evaluation of the reservoir based on fuzzy mathematics is conducted,predicting favorable reservoir distribution areas and pointing out favorable exploration directions.The favorable reservoirs of the Haojiagou Formation are divided into Ⅰ,Ⅱ and Ⅲ.Type Ⅰ reservoirs are mainly distributed in the area controlled by the sedimentary facies of the underwater distributary main channel and the underwater distributary sub-channel,and have the best porosity and permeability performance.Type Ⅱ reservoir is mainly distributed in the area controlled by the sedimentary facies between underwater distributary inter-channel,with poor porosity and permeability performance.Type Ⅲ reservoir is mainly developed in the sedimentary facies of shore shallow lake,with the worst porosity and permeability performance,and the favorable exploration direction is to increase the development of the transition area from the type Ⅰ reservoir to the type Ⅱ reservoir. |
