Seismic Imaging And Reservoir Prediction Of Typical Pre-Salt Carbonate Reservoirs In Pre-Caspian Sea Basin

For pre-salt carbonate reservoirs in Pre-Caspian Sea basin, there are massive saltdomes whose thickness varies from several dozen meters to 3700m and velocitydifference is big from that of the wall rock, which makes the seismic wave field onpre-salt domes becoming very complicated, seismic resolution and signal noise ratiobeing very low, and seismic imaging on salt dome's flanks and pre-salt structuresbecoming very difficult. On the other hand, pre-salt carbonate formations have seriousheterogeneity and the controlling factors to form reservoir are very complicated,which, combined with the seismic events being distorted duo to the effect of saltdomes, enlarges the difficulty in reservoir identification and prediction. This paper,taking the Kenjiyak and Zarnor pre-salt reservoirs of the Pre-Caspian Sea basin as itsresearch objects, presents the study on seismic imaging and reservoir prediction.In the process of study, this paper provides the concepts of the innovation chainand the innovation combination. On the premise of thinking much of innovation spots,we emphasize the function of the innovation chain and the innovation combinationand apply this idea through seismic imaging into reservoir prediction of the carbonatereservoirs successfully.In seismic imaging, a series of techniques for enhancing resolution and signalnoise ratio were adopted, such as pre-stack de-noising, averaging bin size, waveletsform normalization, amplitude compensation in time and frequency domains andspherical spreading compensation, 3D DMO stack as well as Stolt migrationtechniques. Through new round tackling ken problems on seismic processing, seismicprofile quality and seismic resolution were improved, seismic migration locationbecame more reasonable, varied geology bodies became clearer, which then lay downa solid foundation for reservoir prediction.This paper sets forth the united forward and inversion reservoir prediction, whichemphasizes the analysis of geological forward model and screening separately thebest prediction methods for reservoirs of different origins. This approach integratesthe geological forward model with prediction results organically and calibrates andcorrects them interactively to reduce significantly the multi-solutions of seismicinversion.High resolution sequence stratigraphy study was done on this area. Throughstratigraphic correlation, 6 para-sequence group and 16 para-sequences wereidentified in C Formation. Sequence stratigraphy results can provide the frame forreservoir prediction, and so enhance the precision of reservoir prediction.For the features of extraordinarily low porosity and permeability, minor fracturesystem and cave growing in carbonate reservoirs, as well as many other kinds ofinformation such as geology, seismic, logging and reservoir data were combinativelyused to generate the geophysical(log and seismic) response features to differentreservoirs of various origin, which is used as the key prediction factor. Taking seismicprediction as the main thread, and comprehensively using varied seismic attributes ,seismic trace wave classification, spectrum decomposition, coherence property and3D visualization, looking for favorable sediment facies by lithofacies study, searchinggood beds by petrophysical study, and identifying high productive zone by fracturestudy were carried out and then relatively completed workflow and techniques forthe reservoir prediction were formedBased on the result of prediction, a five well in-fill drilling program was set andafter the program was implemented the average daily production rate per well wasraised from 70 to 269 tons, showing very good economic benefit.Pre-salt carbonate reservoir prediction not only has a great theoretical meaning,but produces vast social values.