Steve Checkles

Comparison of Microseismic Results From the Bakken Formation Processed By Three Different Companies: Integration With Surface Seismic And Pumping Data

In May, 2010 Hess acquired its first microseismic survey in the Beaver Lodge area, North Dakota, over a 2-day time period. In conjunction with this project Hess also acquired a walk-around, offset, and zero-offset VSP to enable estimation of azimuthal anisotropy and generation of a 3D velocity model for proper microseismic event placement. Three different companies were contracted to process the data resulting in widely varying microseismic locations. Rather than accepting externally processed microseismic events that show completely different fracture geometries, Hess is developing an internal methodology to review event picking, 3D velocities, and survey geometries that will lead to dependable results.

3D VSP acquisition and 3C processing on a deep subsalt prospect in the Gulf of Mexico

Summary Good quality seismic images can be difficult to achieve in the deepwater, sub-salt sediments of the Gulf of Mexico. 3D vertical seismic profiles (3D VSP), with the receivers placed below the salt, can be a useful technique in improving sub-salt image quality. This paper describes how a 3D VSP was used to prove the existence of reservoir horizons, confirm reservoir dip and generally confirm seismic correlations. Success was achieved by way of several innovations in acquisition and processing. We deployed 40 downhole receivers, the largest array deployed in the Gulf of Mexico at the time of recording. Previously, a survey of this magnitude required several tool settings and several times the rig time. Noise in the data prompted development of station consistent deconvolution, a new casing ringing reduction technique. We also adapted surface seismic techniques for reducing random noise and source noise from a nearby surface seismic shoot. Common image point gathers (CIP) were introduced as a means of verifying the migration velocity model and as quality control tool for the final image stacking.

Reverse Time Migration of P-wave and C-wave Data from a 3D VSP over a Deep Subsalt Prospect in the Gulf of Mexico

Summary Difficulties in imaging subsalt data in the Gulf of Mexico are well documented. Even with the lates t wide azimuth acquisition technology the quality of imaging subsalt is quite variable. 3D VSPs offer the potential to improve reservoir imaging as compared to surface data and to calibrate the reservoir to the surface seismic. The major drawbacks to 3D VSPs are that they are quite expensive due to the rig time required and by their very nature offer a narrow illumination window around the wellbore. To extract more information from 3D VSPs than standard Pwave processing two avenues were investigated: 1) The utilization of the reverse time migration (RTM) imaging algorithm which offers the possibility to increase the lateral coverage of 3D VSPs because it honors two-way propagation and all multiples in the model. 2) Processing for converted wave modes of energy.

A beam approach to Kirchhoff depth imaging

Although Kirchhoff migration is currently the tool of choice for 3-D seismic prestack depth imaging, full volume imaging using Kirchhoff methods is costly for large surveys or interactive processing. This article describes a beam methodology for Kirchhoff imaging that leads to a theoretical speedup of up to two orders of magnitude over traditional implementations of Kirchhoff migration. Beam methodology has been used routinely in Amerada Hess for generating 3-D full-volume prestack depth images for the last several years.

Anisotropic model building by integrating welltie and checkshot for Garden Banks of GoM

Summary In order to improve depth positioning and structural accuracy, we b uild an anisotropic velocity model for imaging Northeastern (NE) Garden Banks in the Gulf of Mexico (GoM). We assume vertical transverse isotropy (VTI) and derive Thomsen’s δ by comparing seismic and well data. Both welltie and checkshot data indicate a twolayer δ trend in NE Garden Banks: low δ shallow and high δ deeper. The interface between the two δ zones corresponds to a distinct seismic reflector – the base of a mass transport complex which is also a local maximum in the velocity. Using this two-layer δ model and a scanned Thomsen’s e model, we carry out anisotropic (VTI) imaging. The VTI imaging reduces misties by more than 80% compared to the original isotropic imaging.

Multiple identification in the image domain using map modeling and map migration

Summary In seismic imaging, a fundamental assumption is that reflection data only consist of primaries. If multiples are not fully removed, they can be misinterpreted as primaries. The purpose of this study is to identify the multiples in the image domain by map-migrating the modeled multiples. This can be used as an interpretation tool to avoid picking residual multiples as primary events. In this abstract, we first describe the theory and method of map modeling and map migration and test this algorithm with a simple linear velocity model and a dipping reflection horizon. Then, we apply it to a field data from the Gulf of Mexico. The results show that this algorithm accurately predicts the location of the specified multiples, allowing the identification of the residual multiples in prestack depth migrated images. Finally, we discuss the limitations of this method and the future directions for development.

Application of elastic modeling to subsalt interpretation

Staggered grid finite difference elastic modeling is used to synthesize point-source responses to a two-dimensional subsurface model derived from three-dimensional preand post-stack depth migrated data volumes. The modeled data are then processed as if they were the result of a real field acquisition process. Comparisons between real data and synthetic responses provide additional confidence in validation of interpretations and drilling decisions.