We propose an efficient and accurate finite-difference approach for modeling the acoustic wave propagation in cased boreholes with micro-annuluses. The presence of micro-annuluses at casing-cement or cement-formation boundaries can result in unconformities that can change the borehole acoustic response. Correction interpretation of the acoustic measurements acquired in such a downhole environment requires conducting numerical simulations to investigate the characteristics of borehole acoustic wave propagation. Traditional numerical methods that use very fine grid to model a micro-annulus are computationally expensive. Because the sonic wave wavelength is generally much larger than the aperture of a micro-annulus, the wave senses only the effective elastic response of a region adjacent to the micro-annulus. We propose to use an effective medium finite difference approach for modeling microannuluses in wave propagation simulations. In this approach, we model a micro-annulus as an effective thin layer embedded between the casing-cement or cement-formation boundaries. Comparisons with the results calculated using a fine grid finite difference approach for borehole models with different micro-annulus settings demonstrate that the proposed method is accurate and computationally efficient in modeling micro-annuluses.
Presentation Date: Monday, September 16, 2019
Session Start Time: 1:50 PM
Presentation Time: 2:40 PM
Location: Poster Station 4
Presentation Type: Poster