Gamma density rapid-calculation method based on perturbation theory

Abstract

The present invention discloses a gamma density rapid-calculation method based on a perturbation theory, and specifically relates to the field of petroleum and natural gas development. According to the method, from a gamma-gamma density response principle, the perturbation theory is introduced to a density response, different standard densities of strata are selected as a reference, and an instrument-stratum model is established in combination with MCNP for simulation to obtain first-order and second-order Compton and photolectric sensitivity function databases, thus forming a gamma-gamma density rapid-calculation method at last. The method specifically includes the following steps: step 1: introducing the perturbation theory into the density response, and performing expansion, deformationand simplification on a formula to obtain a spatial dynamic response function expression form; step 2: according to a parameter of a selected gamma-gamma density instrument, establishing a three-dimensional MCNP numerical calculation model, and simulating to obtain a spatial dynamic response function database; and step 3: performing multielement nonlinear regression on multiple hybrid density responses, and seeking for a coefficient of a rapid calculation formula to obtain the rapid calculation formula for density.

Description

technical field [0001] The invention relates to the field of oil and gas development, in particular to a fast calculation method for gamma density based on perturbation theory. Background technique [0002] Density is one of the important parameters of formation evaluation, mainly used for calculation of formation lithology, porosity and determination of shale content. The rapid calculation of gamma-gamma density logging is of great significance for the inversion of different formation models and the acquisition of formation structure parameters. In addition, fast calculations can improve geosteering, geological modeling and petrophysical evaluation. Real-time predictive modeling of density logs and other logging techniques can also reduce the risks associated with high-deviation and horizontal drilling. [0003] At present, the Monte Carlo numerical simulation method is mainly used for gamma-gamma density calculation. This method has high simulation accuracy, but due to t...

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Problems solved by technology

[0003] At present, the Monte Carlo numerical simulation method is mainly used for the calculation of gamma-gamma density. This method has high simulation accuracy, but due to the limitation of CPU, it has the disadvantages of long time consumption and high cost, and it is difficult to meet the needs of real-time oil and gas evaluation on site.

The Born approximation is one of the most widely used methods for rapid density calculation at home and abroad. Its essence is to use the first-order linear approximation to obtain the density value change caused by the change of the formation model. , the density value of the fast calculation is less accurate

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