| At present,the research and application of unconventional resources are the most important in the field of oil and gas exploration and development.Shale gas and tight gas,for example,are widely distributed around the world and contain huge natural gas resources.Among this,the reserves of tight sandstone gas reservoirs are about 196 trillion cubic meters,accounting for 22% of the world's unconventional natural gas resources and 23.5% of the world's total natural gas resources.In recent years,the research on the development of tight gas in major oil and gas fields is increasing day by day,and the exploration methods for tight sandstone are constantly innovating,which makes the position of tight sandstone reservoir more and more important.The anyue area in the middle of Sichuan basin is a typical tight sandstone gas field,the lithology of which is mainly sand and mudstone,and the oil and gas in the block are mainly concentrated in the Triassic system.The second and third section of the xujiahe formation of the target stratum has a high-quality production-reservoiser-cap combination,with the proved reserves of about 460 billion cubic meters,indicating that the study area has strong exploration potential.Therefore,in this paper,the geological features of the river is the foundation,based on the earthquake response of the rock physics and two aspects,and the corresponding relationship between,in combination with well logging data and seismic reflection principle get regular features in the study area,reflecting the objective interval in good atmosphere,so as to forecast the hydrocarbon reservoir,reduce the uncertainty of seismic interpretation and reservoir prediction.Firstly,the sedimentary tectonic environment is analyzed according to the regional geological situation,and the lithology,physical property and gas bearing property are analyzed according to the geological characteristics of the reservoir.Secondly,in petrophysical analysis,based on shear wave prediction and fluid substitution,abnormal correction and repair of logging curves and high coincidence prediction are carried out,so as to carry out petrophysical modeling and test the fitting effect.According to the characteristics of logging response,the sensitive parameters are screened out,and the sensitive parameters of rock physics are further studied through a lot of statistical analysis of rock physics and cross analysis of elastic parameters of rock physics.Based on a large number of petrophysical statistics,a reservoir geological model is established to lay a foundation for seismic response research.Then,the well seismic calibration is used to link the logging data with the seismic data to prepare for the forward modeling.The abnormal response characteristics were obtained by AVO forward modeling of the actual well,and the forward modeling results were compared and verified by AVO attribute parameter inversion.Finally,variable parameter AVO forward modeling was carried out to further understand the seismic response law,including variable reservoir,cap parameters and variable seismic wavelet.The reservoir parameters were porosity,saturation,double parameters and thickness,cap parameters were cap lithology(mineral content),and seismic wavelet parameters were wavelet frequency.The results of this study are as follows:1?The target strata in the study area experienced multi-stage tectonic cycles,with a complex history of accumulation and a sedimentary background dominated by braided river delta-lake deposits.The lithology of this block is mainly sand and mudstone,and the physical property is relatively good low porosity,and the gas-bearing property is good gas-bearing saturation.2?In petrophysical analysis,the modeling process has a good fitting effect,and a preliminary understanding of the sensitive parameters has been obtained.Through logging response analysis,sensitive parameters were screened out,and through a large number of petrophysical statistics,six parameters that could roughly distinguish lithology and identify reservoirs were obtained,among which density and velocity ratio of horizontal and horizontal waves had the best resolution effect and had certain separability.3?In rock physical analysis,based on a large number of statistical results,a further two-parameter analysis is carried out.In the two-parameter intersection analysis to distinguish lithology,the longitudinal wave impedance and velocity ratio of P-S wave,velocity of longitudinal wave and velocity ratio of P-S wave,lame impedance and shear impedance,lame impedance and velocity ratio of P-S wave,these four groups of parameters have obvious separation tendency,and the best effect is to distinguish sand and mudstone.In the two-parameter crossplot analysis for identifying reservoirs,porosity crossplot analysis is the main method to identify reservoirs and non-reservoirs.Secondly,the three parameter pairs of vertical and horizontal wave velocity,acoustic time difference and density,volume modulus and shear modulus can identify dry layer,aquifer and gas-bearing layer in reservoirs.4?Based on a large number of rock physical statistics,the reservoir geological model was established to lay a foundation for AVO forward modeling.Among them,parameters of the corresponding layered model and part of the layered model were obtained by taking well YUE111 as an example.The combination of reservoir covers of the three gas formations is consistent,and the overall performance is "sand-coated" structure type.Secondly,based on the characteristics of the rock itself,the volume model of the actual well is obtained by taking 6 typical Wells as examples,indicating the overall spatial distribution range,which is mainly divided into oil-gas water layer,gas-bearing water layer and gas-poor water layer,including the rock matrix skeleton dominated by sand and mudstone and the effective pore fluid composed by oil-gas water.5?Seismic response study,based on the well seismic calibration for actual well AVO forward modeling,according to the reservoir distribution position and purpose layer at the top of the distance,classifying the forward modeling results,which shows that the AVO response type mainly for first class IV response.When the gas reservoir is located in the second,three sections of the top,AVO response type characterized by I,IV class.When the gas reservoir is located in the second,three sections of the upper(30 m),AVO response type characterized by IV class.When the gas reservoir is located in must be in the second and third paragraph part(30 m),AVO response type for III,IV class.6?Based on AVO forward modeling results of undisturbed strata,AVO intercept attribute inversion,AVO slope attribute inversion and AVO poisson's ratio attribute inversion were compared and verified,and the results showed that the inversion anomaly corresponds to the forward modeling response characteristics.It not only shows the feasibility of seismic prediction for gas-bearing reservoirs,but also shows the reliability of seismic response characteristics and petrophysical parameters.7?In the AVO forward modeling analysis of variable reservoir parameters,the first type of oil and gas formation of typical well YUE111 is taken as an example.The variation of reservoir parameters includes variable gas-bearing porosity,variable gas-bearing saturation,dual-parameter analysis and variable reservoir thickness.Porosity changes,the AVO response from the first III class to the first IV transformation.Gas saturation changes,the AVO response in the first IV has been change,consistent with the results of typical Wells AVO forward modeling.Porosity and saturation changes in turn,the AVO response has been in the first III class changes.Reservoir thickness change,the AVO response from the first I class to the first IV transformation.8?In the AVO forward modeling analysis of variable cap formation parameters,the first type of oil and gas formation of typical well YUE111 is taken as an example.The change of cap formation parameters is mainly the cap lithology(mineral content).Under the cap rock lithology(mineral content),in turn,change,the AVO response from the first II class to the first III transformation.9?In the AVO forward modeling analysis of variable seismic wavelet,the first type of oil and gas formation of typical well YUE111 is taken as an example.Seismic wavelet frequency variation,the AVO response in the first IV has been change,consistent with the results of typical Wells AVO forward modeling. |
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