Logging Reservoir Evaluation Of The E_1-2z Formation In The Middle Zone Of Southern Junggar Basin

The Huomatu belt is located in Tianshan foreland thrust belt in the southern margin of the Junggar basin.The research area developed three anticline tectonic belts in Mesozoic and Cenozoic,which includes Anjihai anticline,Huoerguosi anticline,Manasi anticline,Tugulu anticline and Hutubi anticline.The E_1-2z formation has become one of the most important oil reservoirs.Even the sandbodies are well developed,the porosity and permeability of reservoirs in some areas are weak,which make it a typical low porosity and low permeability reservoir.At present,low porosity and permeability reservoir has become the main part of exploration and development in China,as well as an important source of new oil reserves and production.The log evaluation of low porosity and permeability reservoirs is of significance in explorating and exploitating the oil reservoirs.Conventional logging interpretation and evaluation technologies are not necessarily suitable for low porosity and permeability reservoirs because of the differences between low permeability reservoir and conventional reservoir in terms of pore structure and physical characteristics of rock surface.How to choose a reasonable interpretation and evaluation method to improve the accuracy and reliability of the result is an urgent problem to be solved at present.Based on the study of basic geological characteristics of the E_1-2z formation,the article analyses the basic features of reservoirs and classifies the pore structure to 3categories with rock thin sections,SEM and mercury injection data,and summarizes the logging response characteristics of each category.We analyse reservoir four property correlations in detail and establish log interpretation template of porosity and permeability for 5 anticline belts.Conventional log recognition chart for pore structure and standard classification are established to predict the pore structure types in study area with a parameter—Iq.We also draw the contour map of reservoir parameters and establish the standard of reservoir classification to sum up the distribution law of high quality reservoirs.Some conclusions are summaried below:?1?The sedimentary facies of the E_1-2z formation are mainly meandering river-delta and braided river-delta.The reservoir is mainly composed of feldspar sandstone or feldspar-debris sandstone.The mainly cementations are calcite and clay mineral particles,which support with the point-line contact.The pore types of E_1-2z reservoir are mainly intergranular and residual intergranular pore.On the basis of morphological characteristics of mercury curve and other parameters of pore,pore structures are divided into 3 types.?2?Through the data of comparison of core,mercury pressure and test oil and log interpretation results,the template for porosity,permeability and shaliness are proved to be accurate.Based on the conventional log recognition chart for pore structure the classification standard of pore structure,reservoir pore structure prediction for uncored wells are completed.The results shows that type?are less than type?,which are only distributing in the Manasi anticline,Hutubi anticline and Tugulu anticline.?3?Plane diagrams of reservoir parameters show that sandbody thickness and the source direction affect porosity and permeability of reservoirs as well as the shaliness.Moreover,sedimentary facies also control the reservoir parameters.Along the extension of the channel and the estuarine dam or the point bar deposition,the reservoir pore permeability is high,the effective thickness is large,the mud content is low,and the pore structure is good.?4?The article combines the plane distribution characteristics of sedimentary facies and reservoir parameters to carry out the reservoir evalution,and divides it to 4types.?5?We are working to find relatively high quality reservoirs,the results show that properties of the E_1-2z₃ reservoir is significantly better than the other layers,which Manasi and Tugulu anticline reservoir quality is better than the rest of the anticline.AnJiHai anticline and Huoerguosi reservoir quality is the worst with no type?reservoir.The effective thickness of Hutubi anticline is up to 150m,but deep buried depth and high shale content lead to the poor reservoir quality.