Research On Stratified Reconstruction Inversion Of Log-seismic Multi-attributes And Its Application In Nantun Formation Of Tanan Depression

Tanan Depression is the secondary tectonic unit Tamuchage basin , belong to continental extensional fault basin of lower cretaceous , the formation divided into Tongbomiao,Nantun,Damoguaihe and Yimin formation from up to down in lower cretaceous. This paper mainly studied Nantun formation in fault-depressed diversionary period, Nantun formation widely developed dark mudstone and underwater fan. The depression and rising depression zone of Ta'nan Depression is the favorable distributed conditions of lithologic reservoir,structures framework of depression and rising controlled the provenance and lithologic body's trend,regulated the reservoir sand body properties. As the provenance is multiple, short, nearly,sedimentary body fast uninstall , reservoir thickness and lateral changes in physical properties of fast , the study area of the lithology prediction is very difficult .Especially the acoustic logging data and density data is the inversion of the basis of information and the fundamental basis for geological interpretation .Therefore,sonic and density of information in a rational manner to deal with the actual geological characteristics to meet a crucial step is the inversion . Conventional inversion processing tended to focus on the acoustic logging data processing,while ignoring the impact of density on the inversion ,even if the processing of the density,often use the Gardner formula only to strike a conversion density,Little change in the lithology of the formation,calibration for this method is feasible thick ,However, the interpretation of high-resolution,the main problem to solve is the problem lithology,accuracy of the density parameter and therefore can not be ignored on the inversion. Therefore, the density data and acoustic data have exerted a profound influence on the inversion results. It is difficult for the conventional calibration program to eliminate the non-formation on the impact of density data,this paper presents a practical and effective log-seismic multi-attributes stratified reconstruct the density curve to resolve this problem.To improve the lithological recognition ability of characteristic curves,the resolution of inversion and the accuracy of reservoir prediction,put forward log-seismic multi-attributes stratified reconstruction characteristic curves technique,using multi log-seismic reflect lithological attributes,focusing on different target bed,reconstructed sonic and density curves individully. Through reconstruction of processing solutions the following questions;â‘ The density curve of log-seismic multi-attributes reconstruction resolved wall collapse, mud invasion, such as the distortion caused by the problem of density logging, So that the density of the response of the lithology in line with the actual geological conditions, improved resolution and accuracy of inversion;â‘¡The sonic curve of log-seismic multi-attributes reconstruction eliminated the effects of high velocity and lithology clearly distinguish between the interface causing by the high-resistivity mudstone,enhanced ability to identify lithology,improved the inversion resolution,reservoir and surrounding rock more obvious differences;â‘¢Stratified reconstruction characteristic curves technique,fine choice of small-scale reservoirs have a good ability to distinguish between the log-seismic attributes,highlighted the purpose of inversion layer profile of geological features,strengthened the ability to distinguish lithologic characteristic curve,improved the inversion resolution.According to the actual situation in the study area,affer binding by high-resolution sequence stratigraphy, by using model-based of logging constrained reconstruction inversion method forecasted lithology of the study area. Inversion process includes several key technical aspects of logging data processing,wavelet extraction,synthetic records, horizon calibration, inversion model building and the main parameters inversion selecting,obtained high-resolution body wave impedance inversion data. Mathematical statistics between the relationship sound speed and the lithology for sequence of the sub-unit in Nantun formation,obtained the velocity- lithology fitting formula of sequence of the sub-units,carried out the forecast of lithologic combining with inversion data,come to sandstone isopach map and rate of sand planar graph for sequence of the sub-units. By inversion of the results before and after reconstruction qualitative analysis,quantitative analysis and attribute authentication to draw that reconstruction after the inversion of the resolution can be improved,the capacity of lithology identification strengthened,lithologic characteristics of the lateral variation,in favor of sand body horizontal tracking and forecasting,characterization spatial distribution of lithology more precise,lithology prediction in line with the rate from 78% to 86%.Through the analysis of lithology prediction results,revealed the law of spatial distribution of lithology the sequence of the sub-units of Nantun Formation in Tanan Depression:sedimentary lithology high-value areas and the sand body thickness center is mainly distributed the side of the fault-controlled basin,in the study area is mainly distributed in the eastern part of near the control fault depression basin zone and near the central fault zone of the western depression. Inversion results of the application identified some special geological phenomenon such as sandstone lenses,maximum flooding surface, nearshore subaqueous fans,the former plot structure etc,and used the results of inversion the to analysis source direction, contemporaneous fault etc.There are still many issues to be further studied for log-seismic multi-attributes stratified reconstruction inversion technique,there are different views on the feasibility of the technology. However,as a method of improving predictive capability of lithology but not contrary to the laws of the methods of geological,should be fully affirmed the value of their practice,we believe this technology will be in constant exploration and practice to further improve the application and development , make its due contribution to petroleum exploration and development.