North Caspian Basin: 2D elastic modeling for seismic imaging of salt and subsalt

摘要

The North Caspian Basin (NCB) contains a significant number of major oilfields, some of which are yet to be put into production. The reason why some of thesefields are not yet put into production is the exploration challenge that the NCB poses. Inparticular, the complex geological structure of this region makes it quite difficult toimage its oil fields with conventional seismic techniques. This thesis sheds more light ondifficulties associated with acquiring and processing seismic data in the NCB. The twocentral tools for investigation of these imaging challenges were the construction of ageological model of the NCB and the use of an accurate elastic wave-propagationtechnique to analyze the capability of seismic to illuminate the geological structures ofthe NCB. Using all available regional and local studies and my knowledge gained withoil companies, where I worked on subsalt and suprasalt 2D and 3D seismic data from theNorth Caspian Basin, I constructed a 2D elastic isotropic 10-by-6 km geological modelof a typical oil field located on the shelf of the Caspian Sea in the southeastern part ofthe North Caspian Basin, which has the largest oil fields. We have propagated seismicwaves through this model. The technique we used to compute wave propagation isknown as the Finite-Difference Modeling (FDM) technique. Generating 314 shot gatherswith stationary multicomponent OBS receivers that were spread over 10 km took twoweeks of CPU time using two parallel computers (8 CPU V880 Sun Microsystems and24 CPU Sun Enterprise). We have made the data available to the public. The dataset canbe uploaded at http://casp.tamu.edu in the SEGY format. The key conclusions of theanalysis of these data are as follows:- Combined usage of P- and S-waves allows us to illuminate subsalt reef, clasticsand complex salt structures despite the 4-km overburden.- Free-surface multiples and guided waves are one of the key processing challengesin NCB, despite relatively shallow (less than 15 m) shelf water.