Carl Regone

Using 3D finite-difference modeling to design wide-azimuth surveys for improved subsalt imaging

Three-dimensional finite-difference modeling studies conducted over subsalt structures in the deepwater Gulf of Mexico confirm the deficiencies of narrow-azimuth towed-streamer surveys and predict significant improvement in image quality with wide-azimuth methods. Finite-difference modeling has provided important design parameters for two separate approaches for wide-azimuth surveys: ocean-bottom receivers distributed in a sparse grid on the ocean floor coupled with a dense grid of source points on the surface, and a wide-azimuth towed-streamer method using multiple seismic vessels in a novel configuration. These two methods complement each other. Ocean-bottom receivers may be used effectively where field development has resulted in many obstacles that might interfere with towed-streamer methods, where the required size of the 3D survey is not too extensive, or where very long offsets are required for all azimuths. Towed-streamer methods are more efficient for large surveys, and key parameters in the wide...

A modeling approach to wide-azimuth design for subsalt imaging

Subsalt image quality in the deepwater Gulf of Mexico is often very poor with conventional narrow-azimuth towed-streamer (NATS) surveys even when the most advanced processing and imaging methods available are used with great care. The reasons most often cited for the poor image quality are failure to adequately suppress free surface multiples, errors in the velocity model, and illumination problems.

VSP Beyond time-to-depth

VSP or vertical seismic profile was originally designed and is currently primarily used to give us time-to-depth for seismic-well ties. Beyond time-to-depth a number of possibilities exist. Recently, there has been considerable interest in VSP imaging (Ray et al., 2003; Paulsson et al., 2004; Hornby et al., 2004; Hornby et al., 2005a), with extensive surveys being acquired both on land and offshore. Modeling studies using full-waveform finite-difference method (FDM) (Payne et al., 1994; Van Gestel et al., 2003) show us what we can image for a particular acquisition geometry and geology, with best image results seen with 3D VSP surveys incorporating a large VSP array in the well and a 2D source pattern acquired using a surface seismic shooting vessel. Traditionally, VSP imaging has been implemented using surface seismic processing algorithms. However, the VSP geometry poses its own challenges and unique opportunities. In this article we explore some imaging methods to attempt to take advantage of the VSP g...

Suppression of coherent noise in 3-D seismology

In reflection seismology, poor data quality is often caused by high levels of coherent noise. This noise can conveniently be divided into three classes: direct‐arrival, ambient, and scattered.

Effects of Changing the Receiver Array Settings On VSP Images

We use imaging of synthetic 2D Vertical Seismic Profile (VSP) data to study the effects of different survey parameters on the final image. Parameters varied in this process were the shot spacing, maximum shot offset, receiver spacing and receiver array length. We first compared the results of collecting VSP data in and below salt and concluded that data collection below salt has significantly better results, as expected. We also studied the effects of changing the receiver spacing and the total receiver array length and show that, for this example, increasing the receiver array length improves the image quality.

Pushing the limits of resolution at Holstein: A case history from the deepwater Gulf of Mexico

The high costs associated with production in deepwater have led to increased business support for acquisition and processing of high-quality seismic for field development. The relatively thin, stacked reservoirs discovered at Holstein Field, which contain significant recoverable hydrocarbon volumes (350 million boe), posed a challenge for development planning.

A 3D finite-difference modeling study of seismic imaging challenges in Bintuni Bay, Irian Jaya Barat

In this paper, we describe how we designed and built two 3D finite difference (FD) models for Bintuni Bay, Irian Jaya Barat to help us understand key subsurface components adversely affecting seismic data quality for clastic reservoirs below thick and karstified carbonates. Our modeling efforts consisted of four main steps: creation of realistic geologic models based on seismic interpretation; construction of 3D velocity and density models based on the geologic model and well data; generation of 3D FD shot records with dense, areal, receiver grids; and depth migration of subsets of shots and receivers corresponding to various acquisition geometries.

On “Using 3D finite-difference modeling to design wide-azimuth surveys for improved subsalt imaging,” , by Gijs J. O. Vermeer

I am pleased that Vermeer finds my paper on finite-difference (FD) modeling to be interesting. However, from his comments regarding my use of reciprocity to design wide-azimuth towed-streamer (WATS) surveys, it is apparent that I failed to explain that point clearly and thereby caused unnecessary confusion. Let me try again. Vermeer states that I assume it is unnecessary to acquire shot-receiver azimuths in all four quadrants because reciprocity would make such measurements redundant. He further states that I use that assumption as the rationale to model and acquire data in only two shot-receiver azimuth quadrants. This is incorrect. Referring to Figure 10 in Regone (2006), I stated: “If we ignore the edges of the 3D survey, and we have sources everywhere we have receivers, we can use reciprocity to eliminate the left half of the receiver patch as shown in Figure 10b.”

Discussion and Reply

I am pleased that Vermeer finds my paper on finite-difference (FD) modeling to be interesting. However, from his comments regarding my use of reciprocity to design wide-azimuth towed-streamer (WATS) surveys, it is apparent that I failed to explain that point clearly and thereby caused unnecessary confusion. Let me try again. Vermeer states that I assume it is unnecessary to acquire shot-receiver azimuths in all four quadrants because reciprocity would make such measurements redundant. He further states that I use that assumption as the rationale to model and acquire data in only two shot-receiver azimuth quadrants. This is incorrect. Referring to Figure 10 in Regone (2006), I stated: “If we ignore the edges of the 3D survey, and we have sources everywhere we have receivers, we can use reciprocity to eliminate the left half of the receiver patch as shown in Figure 10b.”

Discussion and ReplyDiscussion and Reply

I am pleased that Vermeer finds my paper on finite-difference (FD) modeling to be interesting. However, from his comments regarding my use of reciprocity to design wide-azimuth towed-streamer (WATS) surveys, it is apparent that I failed to explain that point clearly and thereby caused unnecessary confusion. Let me try again. Vermeer states that I assume it is unnecessary to acquire shot-receiver azimuths in all four quadrants because reciprocity would make such measurements redundant. He further states that I use that assumption as the rationale to model and acquire data in only two shot-receiver azimuth quadrants. This is incorrect. Referring to Figure 10 in Regone (2006), I stated: “If we ignore the edges of the 3D survey, and we have sources everywhere we have receivers, we can use reciprocity to eliminate the left half of the receiver patch as shown in Figure 10b.”