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We present a next generation seismic source. The Tuned Pulse Source is a new pneumatic seismic source designed to operate with low-pressure air. It releases a large volume of air into the water over a controlled time generating a pulse with a long rise time and a bubble with a long period. The long bubble period produces strong low frequency signal for velocity model building with methods such as Full Waveform Inversion, for imaging subsalt and sub-basalt, and for building blocky reservoir models using Inversion. Compared to airguns, the TPS has a stronger low frequency content and a lower environmental impact.

This work proposes a technique for deriving fast finite-difference algorithms for numerical modelling of acoustic wave propagation in anisotropic media. The technique is deployed in the case of transversely isotropic media to implement a kinematically accurate shear-free fast finite-difference modelling method. This results in a significant reduction of pseudo-shear artifacts compared to similar kinematically accurate finite-difference methods.

Vector fidelity is the ability of a given sensor to record the motion of the seabed as if the sensor was not there. Hence, vector infidelity may come from either poor coupling or from an influence of the sensor package on the seabed around it. To study the implications of ocean bottom node design on coupling and vector fidelity, we analyse data from a field experiment in which several types of nodes have been deployed at close proximity. The data provide a good opportunity to compare the effect of the shape and design of a node on the quality of the data it provides. We have data from nodes with internal and with external sensors, from nodes which are planted, from nodes that are gravitationally coupled, and from nodes with different contact area, and height of centre of inertia. We find variations in the data that are consistent with the node design. We analyse the amount and the form of shear-wave induced noise on the vertical component and of P-wave induced noise on the horizontal components.

Ocean Bottom Stations provide wide-azimuth multi-component data with great advantages for exploration, reservoir characterization, and identification of drilling hazards. However, due to the high cost of deploying OBS nodes, large receiver intervals are used. In practice, poor illumination due to sparse receivers is a major problem. This problem is particularly, but not exclusively, associated with gaps in the coverage of shallow targets, and is greatly exasperated if some OBS nodes fail. The same problem affects both sparse OBS nodes and ocean bottom cables in the cross-line direction. Fortunately there is an effective solution. The first step in our method is the separation of seabed hydrophone and geophone data to upgoing and downgoing waves. Downgoing waves just above the seabed contain only multiples, or ghost reflections. Nevertheless, we image the ghosts, pretending that the data were acquired with a certain equivalent geometry recorded above the sea surface. This alternate surface is the top of a virtual water layer whose thickness is twice the sea depth. We applied this method to OBS data recorded in the North Sea and generated better images from the downgoing ghosts than the images produced conventionally from the primary upgoing waves.

Good vector fidelity is crucial for various multicomponent applications and can be adversely impacted by poor sensor coupling during data acquisition. We present a method to evaluate the ground coupling quality of three-component (3C) sensors during field deployment using ambient seismic noise data. The method utilizes the directional nature of the noise on the three sensor components for coupling assessment. This is believed to be the first method developed to evaluate in situ sensor coupling from ambient noise measurements.

Surface-consistent residual static correction is applied to land data on a routine basis. However, if the statics are large, conventional methods often break down due to, among other reasons, the difficulty to construct a good pilot trace. We developed a large static correction method that constructs the pilot trace by a local robust L1-norm inversion at each CDP location. The local inversion calculates the relative time shifts of the traces within a CDP gather by minimizing the trace-to-trace time difference. A pilot trace is obtained by stacking the CDP gather after aligning the reflectors by applying the time shifts to the traces. Finally, a global L1-norm inversion resolves the source and receiver statics from the time shifts of traces of all CDP gathers relative to their pilot traces. The method is demonstrated with synthetic and real data examples.

1 A18 AN SVD-POLARIZATION FILTER FOR GROUND ROLL ATTENUATION ON MULTICOMPONENT DATA R. KENDALL 1 S. JIM 1 S. RONEN 1 K. DE MEERSMAN 2 1 Veritas Suite 2200 715 – 5 th Avenue SW Calgary Alberta Canada T2P 5A2 2 School of Earth and Environment University of Leeds Leeds LS2 9JT UK Summary By their very nature multicomponent data provide information on the full wavefield and therefore offer new full-wavefield solutions for the ground roll problem. Here we introduce a time domain multicomponent Singular Value Decomposition (SVD) polarization filter that is optimized to remove most ground roll energy while

C-37 COMBINED OCEAN BOTTOM STATIONS AND SURFACE TOWED SEISMIC STREAMERS Abstract 1 We propose to combine sparse multi-component (MC) seismic data with dense single component (1C) data. Such combination of both acquisition operations and data analysis can provide a better value/cost ratio compared to either 1C data alone or MC data alone. Introduction S. RONEN A. RATCLIFFE P. NICHOLS K. MILLS R. LEGGOTT K. HAWKINS and L. SCOTT VeritasDGC Crompton Way Manor Royal Estate Crawley West Sussex RH10 9QN UK MC seismic data have been acquired on the seabed for over a decade. Compared to surface towed streamers such data

A-12 OVER/UNDER ACQUISITION – BREAKING THE RESOLUTION LIMITS S. GRION J. HOBRO J. BARSCH and S. RONEN Summary 1 Seismic resolution is limited by source and receiver ghosts. In marine acquisitions shallow source and receivers increase high frequency content but attenuate the low frequencies fundamental for stratigraphic and structural inversion. On the other hand deep source and receivers enhance the low frequencies at the expense of the high. The combination of data acquired with different cable depths is a solution to this problem and is usually referred to as over/under combination. Over/under can combine in a single image the high-frequency

Long offset streamer data (up to 18 km) and four component (4-C) sea bed data frorn the East Faroes Basin have recently been acquired by Geco-Prakla.

Irregular acquisition geometry is inevitable due to obstacles and cable feathering in 3-D marine surveys and access limitations in 3-D land surveys. The irregularities will damage the fidelity of seismic images, unless they are properly handled in the processing. DMO in particular, must take account of the actual geometry. Black, Schleicher, and Zhang (1993) have developed an anaiytical calibration method that is implemented via the DMO amplitude term. In this paper we extend the DMO calibration to take into account the irregular geometry, and develop a geometrical calibration.

A pressure buildup well test is a measurement of bottomhole pressures in a wellbore beginning while the well is flowing and continuing for a period of several hours or days after the well is shut in . After the well is shut in, no force maintains the low pressure at the well and the tendency toward equilibrium results in a buildup of pressure in the wellbore. The pressure perturbation initiated by shutting in the well, expands about the well, and trends in the measured wellbore pressures may be altered whenever the pressure wave encounters a change in rock or fluid properties .