Adaptive noise estimation and removal method for microseismic data
AssigneeKing Fahd University of Petroleum and Minerals
InventorsNaveed Iqbal, Bo Liu
Life of this patent
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Abstract
A data-driven linear filtering method to recover microseismic signals from noisy data/observations based on statistics of background noise and observation, which are directly extracted from recorded data without prior statistical knowledge of the microseismic source signal. The method does not depend on any specific underlying noise statistics and works for any type of noise, e.g., uncorrelated (random/white Gaussian), temporally correlated and spatially correlated noises. The method is suitable for microquake data sets that are recorded in contrastive noise environments. The method is demonstrated with both field and synthetic data sets and shows a robust performance.
Claims10
An enhanced oil recovery and CO2 storage method, comprising:
- fracking a geologic formation containing an oil and/or gas reservoir;
- injecting CO2 into the fracked geologic formation to produce oil and/or gas from the geological formation;
- during the injecting or during the fracking, monitoring microseismic activity by:
- recording, by a combination of surface-mounted geophones and geophones placed in boreholes, wherein the surface-mounted geophones are disposed in a star pattern with radial arms extending from a center, seismic observation data;
- iteratively performing, by processing circuitry:
- estimating an observation correlation matrix by:
- dividing the seismic observation data into data segments of length N,
- determining correlation elements by sliding a correlation estimation window (CEW) of length L and a filter design window (FDW) of length N, N<L, over the seismic observation data, where N and L are natural numbers, and
- summing correlations of a data element in one of the data segments of length N for each data segment in the CEW to obtain the observation correlation matrix as a matrix of N x N observation correlation elements;
- estimating a noise correlation matrix using the seismic observation data converted to a frequency-domain while sliding the CEW and the FDW over the seismic observation data to obtain a matrix of N×N noise correlation elements;
- structuring a linear filter for each CEW based on a difference between the observation correlation matrix and the noise correlation matrix;
- recovering seismic signals by applying the linear filter to the seismic observation data;
- and
- displaying the seismic observation data and the recovered seismic signals as an indication of the microseismic activity;
- and
- permanently storing the CO2 in the geologic formation.
Dependencies are inferred from the claim text.