Azimuth density logging is used as one of the methods to determine the parameters which include density, interface position and the dip angle in horizontal well formation evaluation. Azimuthal density fast forward modeling as the input of the inversion model directly determines the correction of the pilot model, the real-time inversion of the formation parameters and the accuracy of the reservoir evaluation.

In this paper, combined with Monte Carlo method, the perturbation theory is introduced to realize fast forward of azimuth density in horizontal wells. On the basis of the three-dimensional columnar formation model, the research on the azimuth sensitivity simplifies the numerical calculation model under the premise of ensuring the calculation accuracy, which reduces the calculation difficulty and improves the calculation speed. A fast calculation method of azimuth density is implemented by the Taylor's expansion simplification of the density response formula and the sensitivity function of the perturbation obtained by MNCP simulation. Except that, the complex measurement environment of horizontal well is considered and corrected. The feasibility of the modified method is verified by MCNP and the comparison results of fast calculation and calculation examples of horizontal well.


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