Controlled illumination and seismic acquisition geometry for target-oriented imaging

The conventional method of seismic data acquisition geometry design is based on the assumption of horizontal subsurface reflectors, which often is not suitable for complex structure. We start from a controlled illumination analysis and put forward a method of seismic survey geometry design for target-oriented imaging. The method needs a velocity model obtained by a preliminary seismic interpretation. The one-way Fourier finite-difference wave propagator is used to extrapolate plane wave sources on the target layer to the surface. By analyzing the wave energy distribution at the surface extrapolated from the target layer, the shot or receiver locations needed for target layer imaging can be determined. Numerical tests using the SEG-EAGE salt model suggest that this method is useful for confirming the special seismic acquisition geometry layout for target-oriented imaging.

Resolution assessment of the three-dimensional acquisition geometry of the Anhui experiment in"Geoscience Yangtze Plan"

According to the actual observation conditions of the Yangtze River valley from Anqing city to Maanshan city,we designed the 3D acquisition geometry,and applied the multi-scale checkerboard semblance analysis to assess the preliminary resolution of the designed observation.The checkerboard semblance tests use the refraction and reflection travel-time simultaneous inversion algorithm to quantitatively provide both resolution assessment of velocity structure and Moho topography.The multi-scale checker-board semblance recovery results show that while the chec-kerboard semblance threshold value is 0.5,the preliminary resolution of the designed acquisition geometry is better than 10 km in the upper crust(the depth is less than 10 km),around 15 km in the mid-crust(the depth is 10?25 km),and better than 20 km in the lower crust(the depth is 25?33 km).The preliminary tomographic resolution for the Moho topography is about 20 km in the ray-path coverage area beneath the acquisition geometry.While the checkerboard semblance threshold value is 0.75,the preliminary resolution is 20 km in the upper crust,around 20?25 km in the mid-crust and 25 km in the lower crust.And the preliminary tomographic resolution for the Moho topography is better than 30 km in the ray-path coverage area beneath the acquisition geometry.These non-linear checkerboard tests reveal that the designed acquisition geometry is suitable to image the crustal velocity structure of the Yangtze River valley in the Anhui province.

Seismic Acquisition in the Beach of the Shengli Oilfield

The beach of the Shengli oilfield, as the prospect for steady continuous development of the Shengli oilfield, has a large area, special geographic and geological conditions, and other technical difficulties so that exploration has been slow. Seismic acquisition methods in the beach area and very shallow water have been investigated and, with the introduction of new equipment, given rise to more sophisticated acquisition geometries. A series of improved seismic exploration methods in the beach area and very shallow water are established by analyzing different shot and receiver parameters. As a result, S/N ratio and resolution of seismic data have been improved significantly to identify subsurface structures, improve reservoir description, and increase reserves and production.

Geometric calibration for a SPECT system dedicated to breast imaging

Geometric calibration is critical to the accurate SPECT reconstruction. In this paper, a geometric calibration method was developed for a dedicated breast SPECT system with a tilted parallel beam （TPB） orbit. The acquisition geometry of the breast SPECT was firstly characterized. And then its projection model was established based on the acquisition geometry. Finally, the calibration results were obtained using a nonlinear optimization method that fitted the measured projections to the model. Monte Carlo data of the breast SPECT were used to verify the calibration method. Simulation results showed that the geometric parameters with reasonable accuracy could be obtained by the proposed method.