Borehole gravity drift correction: A new approach

Abstract

Gravity meter drift is the gradual change in the gravity reading over time; this change is unrelated to actual gravity changes. Drift is caused by creep in the gravity meter mechanism and by external influences which produce a change in the physical properties of the gravity element. Previous methods of drift correction for the LaCoste and Romberg borehole gravity meter are either linear random noise filters or nonlinear techniques relying upon the judgement of an interpreter for filtering. The method presented in this paper responds to the nonlinearity of the drift signal while retaining the ability to filter out the noise. The drift rate function is defined by repeat readings, which are integrated to yield a drift correction. The drift correction data’s Fourier transform has a sharp amplitude break between the drift signal and the noise. A low‐pass filter removes the higher frequency noise, resulting in a smoothed drift correction. This drift correction method, which attenuates random errors while retaining the characteristic drift signal, works well with a variety of drift patterns and leads to consistently better quality data.