Mike Jones

Analysis of anomaly correlations

Recognizing correlations between data sets is the basis for rationalizing geophysical interpretation and theory. Procedures are presented that constitute an effective process for identifying correlative features between two or more digital data sets. The procedures include the development of normalization factors from the mean and variance properties of the data sets. Using these factors, the data sets may be transformed so that they have common amplitude ranges, means, and variances, thereby allowing a common graphical representation of the data sets that facilitates the visualization of feature correlations. Anomaly features that show direct, inverse, or no correlations between data sets may be separated by the application of correlation filters in the frequency domains of the data sets. The correlation filter passes or rejects wavenumbers between coregistered data sets based on the correlation coefficient between common wavenumbers as given by the cosine of their phase difference. Standardizing and summing the filtered outputs where directly correlative features have been enhanced yields local favorability indices that optimize the perception of these features. Differencing the standardized outputs where inversely correlative features have been enhanced, on the other hand, provides favorability indices that improve the perception of the inverse correlations. This study includes a generic example, as well as magnetic and gravity anomaly profile examples that illustrate the usefulness of these procedures for extracting correlative features between digital data sets.

Use of anisotropy in P-wave and S-wave data for fracture characterization in a naturally fractured gas reservoir

Gas production in Bluebell‐Altamont Field in northeastern Utah is from numerous sandstones and carbonates in the Tertiary upper Green River Formation at depths of approximately 6500–8500 ft. The local geologic setting is nearly flat‐lying sediments with no faulting observed at target depths. The field has a very gentle anticlinal closure (less than 50 ft). Matrix porosity and permeability in the reservoir rocks are generally low, such that fracturing yields substantially higher production rates. Consequently, seismic detection of fracturing is a potentially important aid to field development.

Spectral correlation of magnetic and gravity anomalies of Ohio

Geologic interpretation of Ohios magnetic or gravity anomalies is hindered by the effects of anomaly superposition and source ambiguity inherent to potential field analysis. A common approach to minimizing interpretational ambiguities is to consider analyses of anomaly correlations. A spectral procedure is adapted which correlates anomaly fields in the frequency domain to produce filters separating positively and negatively correlated, as well as null correlated features. The correlation filter passes or rejects wavenumbers between coregistered fields based on the correlation coefficient between common wavenumbers as given by the cosine of their phase difference. This procedure is applied to reduced‐to‐pole magnetic and first vertical derivative gravity anomalies of Ohio for mapping correlative magnetization and density contrasts within the basement rocks. The analysis reveals predominantly positive correlations between anomaly maxima and minima. Correlative anomaly maxima may be generally modeled as maf...

White rose seismic with well data constraints: A case history

Interpreters are always seeking improvements to seismic data in quality, resolution, and the accuracy with which the data represent the underlying geology. Consistency of the seismic image with known control points, usually wells, is essential. The bridge between the high-resolution, geographically sparse, depth-indexed world of logs and the low-resolution, geographically ubiquitous and time-indexed world of seismic is the vertical seismic profile (VSP) in its various geometries.

AfricaArray: Developing a geosciences workforce for Africa's natural resource sector

Geoscientists from across Africa, the United States, and Europe are building a pan-African initiative, AfricaArray, to strengthen geoscience education and research programs in Africa and to create an Africa-to-Africa academic support system. Universities, government agencies, and exploration companies are benefiting from the establishment of AfricaArray training programs coupled to a network of geophysical observatories spanning the continent. The observatory network provides support to the training programs and fosters community building by catalyzing collaborative projects and encouraging data sharing.

Time-lapse Monitoring of CO2 EOR and Storage with Walkaway VSPs

Summary At the Violet Grove pilot project, 100 km southwest of Edmonton, Alberta, CO2 is being injected into the Cardium Formation in the Pembina Oil Field for enhanced recovery and carbon sequestration purposes. The reservoir is being monitored using simultaneously acquired time-lapse multicomponent surface and borehole seismic surveys. The baseline survey was acquired in March 2005 prior to CO2 injection. The first monitor survey was acquired in December 2005 after eight months of CO2 injection. The borehole seismic data displays higher bandwidth and increased resolution than the surface seismic data. Comparisons between the baseline and monitor borehole seismic surveys show an increase in reflectivity at the reservoir, and crosscorrelations show a time shift of 0.2 ms on two of the walkaway lines.