Fine Reservoir Description Of 4-8 Area Of HDD Oil Field

After the breakthrough in the Carboniferous Donghe sandstone of HDD Oilfield in 1998,previous studies have carried out a number of special topics on the research area.With the deepening of development,there are many new problems to be solved:a lot of new wells in the study area which have already been drilled out have not been thoroughly studied;the accuracy of log interpretation needs to be improved,so as to prepare for the further research;lack of standard for the classification of the interlayers based on logging;unclear relationship between the interlayer and the sand;the accuracy of heterogeneity study needs to be improved.In view of the above problems and to deepen the understanding of reservoir geology,fine reservoir description is imperative to carry out.In this paper,according to the geological characteristics of HDD Oilfield,based on geological,core and well logging data,a number of research work has been carried out including thin layer division,reservoir parameter interpretation,recognition and distribution research of interlayers and single sand layer and storage layer comprehensive evaluation research content,the main achievements are as follows:Statistical analysis of the data which includ the core,oil and logging shows that,the main lithology of the study area is the gray white fine sandstone;the reservoir has good physical properties;in the well logging curve,the GR and SP of Donghe sandstone present as a box with a slightly serrated appearance;the highest percentage of the oil level is Oily and Oil invasion.Four-property relationship in the study area is more coarse rock,higher level of oil,better physical properties,lower density value,higher value of sound wave and neutron.Using the principles of high resolution sequence stratigraphy,and combining core and logging data,the Donghe sandstone can be divided into one sequence,two parasequence and eight small layers.The under donghe sandstone was deposition towards the coastr for sea level rise,and the upper donghe sandstone was deposited seaward for sea level fall.Horizontally,from the northwest to southeast,the deposition of Donghe sandstone is stable,without obvious lack of formation;from northeast to southwest,the thickness of the southwest is thick while the northeast is thin.Overall the sedimentary strata are thick in the southwest and thin in the northeast on plane.Based on the core depth measurement curve correction,depth migration,log standardization and normalization,the neural network method is determined to be suitable for the reservoir parameter interpretation model in this area,through a variety of methods contrasting.By the test of accuracy of the model,overlap method and error statistics method,it can be concluded that the reservoir parameter interpretation accuracy is good,core analysis value and the corresponding prediction curve points have good numerical agreement,and the error is small.According to the lithology,the interlayer of the study area can be divided into three types:calcareous intercalation,physical and mud.According to the difference of the interlayer's structure,the interlayer can be divided into stripe-strip layered calcareous interlayer,porphyritic-lumpy calcareous interlayer,strip-layered calcium mud interlayer,porphyritic and lumpy calcareous argillaceous interlayer and banded and laminated shale interlayer.Based on the obvious degree of logging response,the interlayers are divided into level one,two and three.Based on the shape of formation dip angle curve,combining with sedimentary microfacies,the single sand layer in the study area are divided into 6 categories:high amplitude box,low amplitude box,finger shape,bell shape,infundibuliform shape and sawtooth shape,the main type is high amplitude box.Based on the sedimentary model of the study area,the connection mode of single sand body in the local area can be summarized as 8 kinds:continuous type,superposition type,upper type,lower super type,lens type,cutting type,lens shaped interlayer branching type and thick layer sand body branching type,at the same time,having the comparison of single sand of the wells based on these patterns.The main single sand body connection mode of the research area are continuous type and superposition type.The Donghe sandstone can be divided into 20 single ones based on the single sand classification of every well.Based on the identification of single sand and the interlayer,a research on the macroscopic heterogeneity of reservoir is carried out from three aspects:the plane,the inner layer and interlamination.By the calculation results of the single sand layers in J_k,K_p,V_k and T_k,the single sand whih have the strongest heterogeneity in the inner layer are S2-1,S2-2 and S5-1.By drawing the cross-plot between the reciprocal of ordinal number and the reciprocal of contribution rate of permeability,the coefficient of heterogeneity of each single sand is achieved to evaluate the strength of heterogeneity in interlamination,results show that S1-1,S2-1 and S5-1 are the strongest ones.On plane,by the thickness composite map,porosity contour map and permeability contour map of the single sand,the heterogeneity of S1-1,S2-1,S4-2,and S5-1 single sand are deemed to be the strongest.In summary,the single sand which have the strongest heterogeneity are S1-1,S2-1,S4-2,and S5-1.The lower limit of porosity for Donghe sandstone is confirmed as 9%,and the lower limit of permeability is 5.1×10^-3?m²,by synthesizing a variety of methods including test method,distribution function method and irreducible water saturation method.Grey theory method is used to carry on the comprehensive evaluation of reservoir.The parent sequence is effective thickness of reservoir,and subsequence are porosity,permeability,V_k and T_k.The comprehensive score of reservoir evaluation of single sand in each well is obtained after a series of calculations,including the normalization,the correlation coefficient,the correlation degree and the weight coefficient.The interface of the reservoir classification is 0.4 and 0.6.Statistical results show that:Horizontally,?and?reservoirs mainly distributed in the upper part of the Donghe sandstone while the?reservoirs mainly distributed in the lower part.On plane,?and?reservoirs distribute in large area of Donghe sandstone.Based on the sedimentary facie,the obtained results from the comparison and analysis of the overlapping graph between the contour of the reservoir classification plan and single sand thickness composite map,porosity contour map,permeability contour map are as follows:the high quality reservoir area of S4-1 single sand located in L26well area which is in the north central of the study area and L29 well area which is in the midwest;the high quality reservoir area of S5-2 single sand located in L16 well area whith is in the north of the study area and the L15 well area located in the south central,the L15 well area is the best one.