A study on gravity field downward continuation using the regularized equivalent-layer method

In recent years, dynamic reservoir monitoring technology using time-lapse microgravity method has been receiving much attention of researchers at home and abroad. As a result of the low signal to noise ratio (SNR) and weak signal in observation data, it is impossible to quantitatively interpret fluid migration in reservoirs using time-lapse microgravity data. In order to suppress observation noise and enhance weak signals, this article presents the regularized equivalent source downward continuation (RESDC) method, and derives the RESDC operator in the wavenumber domain. Besides, the iterative compensation algorithm is proposed to compensate for amplitude attenuation of the downward continuation field. With tests on synthetic data, this work further studies the wavenumber response of the filtering operators and the downward continuation operators of regularized equivalent layers at different depths. Results show that the downward continuation field of the RESDC method is more accurate and stable compared with the field from the Tikhonov downward continuation method. Applying the iterative compensation RESDC method to field data of a time-lapse microgravity survey verifies that the proposed method can effectively enhance weak signals and stably realizes large-depth downward continuation.