Calibration Of Seismic Data Research Articles

A laboratory approach for the calibration of seismic data in the western part of the Swiss Molasse Basin: the case history of well Humilly-2 (France) in the Geneva area

A collection of 81 plugs were obtained from the Humilly-2 borehole (France), that reached the Permo-Carboniferous sediments at a depth of 3051 m. Experimental measurements of physical parameters and mineralogical analysis were performed to explore the links between sedimentary facies and seismic characteristics and provide a key tool in the interpretation of seismic field data in terms of geological formations. The plugs, cylinders of 22.5 mm in diameter and sim30 mm in length were collected parallel and perpendicular to the bedding in order to explore their anisotropy. Ultrasound wave propagation was measured at increasing confining pressure conditions up to 260 MPa, a pressure where all micro-fractures are considered closed. The derivatives of velocities with pressure were established, allowing the simulation of lithological transitions at in-situ conditions. At room conditions, measured grain densities (kg/m3) range from 2630 to 2948 and velocities vary from 4339 to 6771 and 2460 to 3975 {text {m/s}} for P- and S-waves propagation modes, respectively. The largest seismic-reflections coefficients were calculated for the interface between the evaporitic facies of the Keuper (Lettenkohle) and the underlying Muschelkalk carbonates (R_{text {c}}= 0.3). The effective porosity has the range of 0.23% to 16.65%, while the maximum fluid permeability left( text {m}^{text {2}}right) is 9.1 times text {10}^{-{text {16}}}. A positive correlation between porosity and ultrasound velocity has been observed for P- and S-waves. The link between velocities and modal content of quartz, dolomite, calcite, and micas has been explored. This paper presents a unique set of seismic parameters potentially useful for the calibration of seismic data in the Geneva Molasse Basin.

A rapid seismic data calibration technique using integrated micro-electro-mechanical system inertial sensor groups for a 3C vertical seismic profile

Calibration of 3C vertical seismic profile (VSP) data is an exciting challenge because the orientation of the tool is random when only seismic data are considered. We have augmented the sensor package on the VSP tool with micro-electro-mechanical system (MEMS) inertial sensors and applied a gesture measuring method to determine the tool orientation and calibration. This technique can quickly produce high precision, orientation, and angle information when integrated with the seismometer. The augmented sensor package consists of a low-cost triaxial MEMS gyroscope, an electronic compass, and an accelerometer. The technique to process the gesture information is based on the OpenGL software for 3D modeling. We have tested this approach on a large number of field data sets and it appeared to be faster and more reliable than other approaches.

ABSTRACT: Calibration of Seismic Data from the Western Margin of Great Bahama Bank with Exposed Strata in the Maiella Mountains (Italy)

ABSTRACT: Calibration of Seismic Data from the Western Margin of Great Bahama Bank with Exposed Strata in the Maiella Mountains (Italy)

The geodynamic evolution of the Precaspian Basin (Kazakhstan) along a north–south section

Several hypotheses exist for the origin and evolution of the Precaspian Basin. There are more than 20 km of sediments deposited, yet there is little consensus on the causes of the subsidence. Except for the presence of a thick salt layer (Lower Permian), the main problem is the chronostratigraphic interpretation of the sediments in the centre of the basin, where the calibration of seismic data with well data from the basin margins is problematic at deep levels. The age of the deepest sediments could be either Riphean or Devonian. A generalised cross-section of the Precaspian Basin, roughly perpendicular to the central elongated E–W depocentre, is used to represent the basin's evolution. Several evolutionary steps from the end of the Riphean until the Present are demonstrated. Tectonic subsidence analysis indicates that there are six main phases of evolution: (1) subsidence during an active rifting phase in Riphean times; (2) rifting during the Vendian–Ordovician (poorly dated); (3) significant subsidence during the Late Devonian in an extensional context possibly due to back-arc rifting; (4) acceleration of subsidence during the Late Carboniferous–Permian, synchronous with or just following the closure of the Uralian Ocean, a major subsidence phase in the Dniepr–Donets Basin and possible subduction to the south of the basin; (5) renewed rifting during the Triassic coincident with a general phase of extension in Eurasia and the opening of the Neo-Tethys; and (6) neotectonic subsidence resulting from crustal down-bending in a generally compressional setting. The nature of the crust underlying the basin is not well known. It could be Riphean–early Palaeozoic or Devonian oceanic crust or continental crust attenuated during the several episodes of supposed rifting between the Riphean and the Triassic. Estimations of crustal thickness in the basin vary and they depend on the interpretation of a high-velocity layer situated at the base of the crust. The presence and general distribution of this layer is confirmed by gravity data. It may be considered as the uppermost mantle, as oceanic crust metamorphosed into eclogite at depth during collision and then exhumed and emplaced at the base of the crust, or as lower crust transformed in situ (into eclogites?). The crustal thinning factor leading to the observed present crustal thickness — assuming an initial thickness of 40 km — is 3.3 in the two first cases and 2 in the latter, if the crust is considered to be continental. The geophysical and subsidence data are discussed in terms of basin-forming mechanisms such as: (1) intracontinental rifting of early Palaeozoic, Devonian or Permo–Triassic ages; (2) oceanisation of continental crust during Riphean or Devonian time; (3) eclogititisation at the base of the crust in the upper mantle or by metamorphism of subducted oceanic crust; and (4) down-bending due to compressional forces or mantle flow induced by subduction–collision processes in Carboniferous and Recent times.

AN INVESTIGATION INTO DISCREPANCIES BETWEEN SONIC LOG AND SEISMIC CHECK SPOT VELOCITIES

Well data, and in particular Sonic Logs, are the basis for calibration of seismic data leading to improved reservoir delineation. Sonic data are adjusted to match seismic times by comparison to check shots. Recent improvements in Sonic Logging tend to show that, on average, Sonic velocities are faster than seismic velocities. The main reason appears to be frequency dependance of velocities.