用模拟退火法作AVA反演

AVA INVERSION BY USE OF SIMULATED ANNEALING

As a Monte Carlo technique for optimization problems, Simulated Annealing has been recently introdued into geophysics. This paper describes its foundamcntal concepts and practical schemes. Simulated Annealing can be implemented in two versions, namely the Metropolis and heatlth algorithms. Both of them are used by the author in prcstack amplitude inversion, i. c, the inversion of amplitude versus incidence (AVA) data. The results from inversion on a synthetic dataset and two ultrasonic modeling datasets show that Simulated Annealing is appropriate for solving nonlinear optimization problems. The method is independent of the initial guess model and especially easy to accept contraints on cither model parameters or con-troling conditions. The difficicncy is that the method calls for fast forward computations. In spite of the severe ambiguity of the solution in AVA inversion because of strong AVA equivalence, the resalts still reveal the elastic features for the media. This demonstrates the applicability of AVA inversion in estimating the lithology and hydrocarbon occurrence for strata.