First Break - Volume 26, Issue 7, 2008

The viability of many low-permeability reservoirs often depends on hydraulic fracture stimulation and re-stimulation programmes. Understanding the effect of the fracturing process on a formation is critical to designing a successful stimulation program and optimizing reservoir production.

Dealing with the pervasive salt blanket has become a way of life in deepwater Gulf of Mexico exploration. Since the advent of prestack depth migration (PSDM) enabled the identification of potential reservoirs beneath the salt, explorationists and engineers have been consumed with trying to get a better look below the salt. To be sure, surface techniques have improved considerably over the last decade with wide azimuth (WAZ) multiple azimuth (MAZ) and rich azimuth (RAZ) techniques providing increasingly better detail.

Companies today have a need to better understand and monitor the production from their existing reservoirs. With the proliferation of large borehole geophone arrays, 3D VSP has become a viable option for monitoring what’s happening around a well. With geophones fixed in the borehole below the surface, increased resolution at the reservoir level is possible. In this article we will look at the processing of a 3D VSP volume and some of the complexities involved.

Knowledge management is the latest ‘buzz word’ in the exploration and production (E&P) industry – it is used rather loosely to define all activities from data archiving to information management to managing business intelligence methods.

Schlumberger chairman Andrew Gould recently delivered this service company view on the dynamics of global energy security at the Deloitte Energy Conference in May. The message is daunting for the oil and gas business in its efforts to meet global demand for its products but is worth sharing with the geoscience community

An upper limit to the compliance of individual fractures within a reservoir can be determined, given estimates of the effective confining pressure at reservoir depths and the mean aperture of open fractures which is usually obtained from core and well log analysis. The value can then be used with elastic wave numerical modelling to determine an upper limit to the seismic velocity anisotropy that would result from any specified reservoir discrete fracture model. This provides a level of confidence when using seismic anisotropy as an indicator of the presence of fractures that could contribute significantly to reservoir permeability. The least certain aspect of the proposed methodology is the estimate of the ratio of normal to shear fracture compliance.

An upper limit to the compliance of individual fractures within a reservoir can be determined, given estimates of the effective confining pressure at reservoir depths and the mean aperture of open fractures which is usually obtained from core and well log analysis. The value can then be used with elastic wave numerical modelling to determine an upper limit to the seismic velocity anisotropy that would result from any specified reservoir discrete fracture model. This provides a level of confidence when using seismic anisotropy as an indicator of the presence of fractures that could contribute significantly to reservoir permeability. The least certain aspect of the proposed methodology is the estimate of the ratio of normal to shear fracture compliance.