SEISMIC INVERSION AND THE IMPACT OF A PRIORI INFORMATION: Advanced Geophysical Modeling and Inversion Unification (AGU): Final Report of the GEOSCIENCE Project JOUF-0037

摘要: Over the past decade, theory and experiments have shown that changes of reflection amplitude with offset (AVO) in multi-offset seismic records are strongly affected by relative Poisson's ratio. AVO analysis opens possibility to distinguish ‘bright spots’ due gas accumulation from those caused other lithology AVO is generally carried out ray tracing Zoeppritz equations as tools for forward modeling. Some inversion procedures been developed infer contrast elastic parameters. However, it was recognized quality available modeling techniques insufficient. The alternative approach we propose (i) an extension reflectivity method smoothly varying media, (ii) a cost-efficient linearized finite-difference technique.In our study minimized structural difficulties order concentrate on 2D target zone quasi-layered background media. Then small parameter contrasts can be estimated using linear least-squares approach: waveform match between synthetic gathers obtained perturbing model parameters zone. We also evaluated impact use priori information. Finally non-linear has understand what reservoir-scale information contained data. Participants this project were AGIP (Italian oil company), Politecnico di Milano(POLIMI) Institut Francais du Petrole (IFP). Each partner contributed specialskills experience. The task AGIP, industrial partner, analyse real data ase maximum depth possible, extract all parameters.The role academic Milano, improve evaluate uncertainties both amplitude-versus-offset studies overburden noise data. An effort made implement technique (ω-k domain. IFP develop finite differences, large-scale set. In addition, multidisciplinary team numerical simulation bas d controlled earth followed processing interpretation. Part I deals inversion.It decided most accurate technique, i.e., well known method, so better represents shorter offsets; subsequently extended media vary continuously depth, lateral direction. This achieved hybridization methods. A powerful (and essentially exact) 3D resulted, albeit limited quasi ID group able case suitable kind careful systematic comparison elastically modeled interpretation steps described below. Another important step determine error bars inversion. For this, useful move problem spatial domain frequency-wave number opened bette ‘conditioning‘. The ω-k (with some preliminary results) presented It necessary not only inversion, but limits general. To end complete interaction velocity errors out. thorough understanding particularly if perfectly analysed. Part II describes its evaluation data.A procedure based computation Jacobian matrix differences proposed, analysed implemented. Its accuracy tested models containing few scattering points. Besides modeling, formulation implemented find perturbations generated Next set gas-bearing sand full-wave code inverted. show that, plane stratified reference medium windows centered reflected P-P waves, one band-limited P-impedance - lesser degree S-impedance at reasonable effort. addition results closer actual than more conventional procedures. Part III Mesaverde outcrop.The objective geological embodied used delineate characterize reservoirs. Both constructed outcrop logs equivalent formations. (marine) propagation code. Conventional applied obtain stacked section. section calibrated impedance theoretical locations (this process corresponds wavelet-extraction processing). complementary direct inverse stratigraphie build likely give significance variations.