Comparison Of Rock Physics And Well-seismic Characteristics Of The Fourth Section Of Dengying Formation In Gaomo Area

So far,the proportion of large-scale carbonate oil and gas fields in the world has accounted for about 32% of all large oil and gas fields.Oil and gas recoverable reserves can reach 133×108 oil equivalent,it accounts for about 47% of the total recoverable reserves in the world.With the discovery of large-scale oil and gas fields throughout the country in carbonate reservoirs,the status of carbonate reservoirs is increasing day by day,for its exploration methods are also constantly developing.The lithology of Gaomo block is mainly carbonate rock,Located in the Sichuan Basin,the largest superimposed petroleum-bearing basin in the South China,the oil and gas in the reservoirs in the study area are mainly concentrated in the Sinian system,the fourth section of Dengying Formation has a high-quality combination of raw and storage lids,the proved reserves are 400×108m3,it shows that the research area has strong exploration potential.In order to analyze the regularity of the gas-bearing reservoirs in the target strata of the study area and to predict the gas-bearing properties of the reservoirs,this article is based on the geological characteristics of the fourth section of Dengying Formation.The analysis of the mutual correspondence between logging response characteristics and seismic response characteristics and the two aspects are performed.First through rock physics analysis,using S-wave prediction and fluid replacement techniques to better predict and reconcile the shear wave velocity and density curves in logging data which is rock physics modeling,then test its accuracy.Through rock physics modeling,the petrophysical sensitive parameters and sensitive parameters of the reservoir are screened out,to find out the sensitive parameters for abnormal reservoir performance.Then conduct a comparative analysis of logging data and seismic data.Through well seismic calibration,using logging data to calibrate on seismic data,thereby binding the two together,at the same time lay the foundation for forward modelling.After the forward modelling of the AVO real well,to find the law of AVO response characteristics.In order to verify the correctness of the found law,we also performed AVO intercept property inversion,AVO slope property inversion,and AVO Poisson's ratio property inversion.Finally,the AVO forward modeling of variable parameters was analyzed and studied,including AVO forward modeling of variable cover parameters and variable reservoir parameters,the former is a forward simulation of variable cover thickness,the latter is a forward modeling of variable porosity,variable gas saturation,and varying reservoir thickness.The results obtained by the Institute of this paper are as follows:1.In the rock physics analysis process,the petrophysical sensitive parameters and sensitive parameter pairs of the reservoir were screened through rock physics modeling,to find out the sensitive parameters of abnormal reservoir performance.Through single-well logging response characteristics analysis,it is relatively good to find the resolution of the ratio of longitudinal wave to shear wave and the P-wave impedance.It can better distinguish the gas layer,poor gas layer and non-reservoir,with a certain degree of dissimilarity,however,the degree of overlap is still slightly higher.2.In the rock physics analysis process,through elastic parameter sensitive analysis,analyze the intersection of multiple parameters,in the porosity analysis analysis chart,the two-parameter intersection plots of P-wave impedance and P-wave velocity ratio can be used to distinguish the gas layer,differential gas layer and nonreservoir in the reservoir section,however,it is greatly affected by the siliceous content,abnormal values that partly reflect the nature of the reservoir show non-reservoir characteristics,therefore,the two-parameter intersection can better distinguish between reservoirs and non-reservoir,it can also better distinguish the non-reservoir or siliceous layer affected by siliceous.In the analysis chart of gas-bearing sex intersection,it can be concluded that the Poisson's ratio-density dual-parameter intersection can distinguish the gas-bearing properties of the formation to a certain extent,although the dissimilarity is slightly worse than that in the porosity analysis analysis chart,however,it can be analyzed that the low-density,low-Poisson's ratio properties correspond to higher gas-bearing sites.3.In the well-shake comparison analysis process,through the forward simulation analysis of AVO actual wells,it is concluded that the AVO response types can be classified by analyzing the distance relationship between the distribution of the gas layer and the top of the target layer,that is,when the gas reservoir is located at the top of the fourth section of Dengying Formation,the AVO response type represents the type I response type;when the gas pool is located about 20 m from the top and above,AVO Response Type Shows Type III AVO Response;in the case of a well,the AVO response type appears as a type IV AVO response.4.In the well-shake comparison analysis process,inverse analysis of forward modeling is performed through AVO intercept property inversion,AVO slope property inversion,and AVO Poisson's ratio property inversion.We can find that the anomaly obtained by the inversion and the AVO forward simulated anomaly response characteristics of the actual well can correspond to each other,this verifies the consistency of the well-shake relationship.At the same time,the credibility of forward modeling and petrophysical sensitive parameter analysis results was further verified.5.The AVO forward modeling of the variable capping parameters was performed on the Well Gaoshi 2 in the typical well,that is,the forward simulation of variable cover thickness.AVO forward modeling by varying cap thickness is concluded that the thickness of a set of dense limestone above the gas layer can affect the abnormal response characteristics of the gas layer.When the thickness of the limestone caprock is relatively thin,the type of abnormal response manifests itself as Class I,however,when the thickness of the cover gradually increases to 20 meters or more,the anomalous response characteristics of the gas layer are converted from Class I to Class III.6.The AVO forward modeling of variable reservoir parameters was performed on the Well Gaoshi 2 in the typical well,that is,forward modeling of variable porosity,variable gas saturation,and reservoir thickness.The AVO forward modeling by changing the porosity in the reservoir parameters shows that the AVO response is always changing in class III,this is consistent with the type of AVO response of the actual well;the AVO forward modeling by varying gas saturation shows that the type of AVO response has been Class III,this is consistent with the type of AVO response of the actual well;through the AVO forward simulation of changing reservoir thickness,the AVO response was converted from category IV to category III.