Steve Cole

Do I Know You?: The Role of Significant Others in General Social Perception

This research used an idiographic method to examine the proposition that significant others are mentally represented as well-organized person categories that can influence social perception even more than representations of nonsignificant others, stereotypes, or traits. Together, Studies 1 and 2 showed that significant-other representations are richer, more distinctive, and more cognitively accessible than the other categories. Study 3 replicated the accessibility data and gauged inferential power by indirectly activating each category in a learning trial about a fictional person and then testing recognition memory. The results showed that participants made more category-consistent false-positive errors about targets who activated significant others vs. any other category. This constitutes the first experimental demonstration of transference and has implications both for social categorization and for basic personality processes.

4D Seismic Data Processing Issues And Examples

4D seismic data acquisition efforts can be divided into three major categories: “legacy”, “re-shoot” and “4Ddesign ” projects. In legacy 4D seismic projects, multiple vintages of overlapping 3D seismic data sets are analyzed for time-lapse effects, but none of the 3D surveys were originally acquired with a 4D application in mind. In reshoot 4D seismic projects, the baseline 3D seismic survey was not acquired for 4D purposes, but the subsequent reshoot 3D survey was designed, at least in part, with a 4D objective in mind. Finally, in 4D-design projects, at least two of the time-lapse 3D seismic surveys were specifically designed and acquired to optimize the subsequent reservoir monitoring analysis.

Estimation of Reservoir Pressure And Saturations By Crossplot Inversion of 4D Seismic Attributes

We present a method to simultaneously estimate pressure and saturation changes in a producing hydrocarbon reservoir using time-lapse (4D) seismic attributes. 4D seismic attributes are displayed in a crossplot domain, where pressure and saturation axes can be estimated deterministically or interpretively. These axes form the basis for a linear or nonlinear coordinate transformation to the pressure-saturation domain. A final calibration to production data is required to convert the qualitative results to quantitative estimates of pressure and saturation. Our method is applied to 4D seismic data sets acquired over producing North Sea reservoirs in the Schiehallion and Gullfaks fields.

Seismic monitoring of CO2 geo-sequestration: realistic capabilities and limitations

Summary Seismic is useful for monitoring and verification of subsurface geo-sequestration CO2 injection and storage projects. The physical properties of CO2-saturated rocks can vary strongly, thus the resulting seismic wavefield can be rich and complex, posing significant challenges to obtain accurate CO2 images and quantitative inversion results. We discuss the seismic rock and fluid properties of CO2-saturated rocks under various realistic pressure and temperature conditions, show the effects of CO2 injection with realistic 3D models and finite-difference simulated seismic data, and compare simulation data images and inversion results to real seismic data at the Sleipner CO2 sequestration site. Rock and fluid physics In this paper we focus on the geo-sequestration application of injecting CO2 into subsurface porous and permeable brine-saturated rock formations for long-term storage. For many geo-sequestration sites and timescales of interest, the depth, pressure and temperature of the reservoir storage rocks will imply that the bulk of injected CO2 will be in an immiscible supercritical phase above the critical point (Pc = 7.38 MPa, Tc = 31.1 o C) in the phase diagram, thus having physical properties of both a gas and fluid. Figure 1 shows our calculations of the bulk modulus (incompressibility) and density of CO2 at various pressure and temperature conditions. CO2 is a gas below the red line, a fluid above the red line, and supercritical to the right of the red line in the phase diagram. The (P,T) conditions for Sleipner are plotted on the diagrams (red circle) and clearly fall within the supercritical region, as most sequestration projects are likely to do (dashed yellow box). Note that the compressibility and density of CO2 can vary as much as one order of magnitude across the geo-sequestration (P,T) range, especially at higher pressures (depths). Figure 2 shows seismic P- and S-wave velocity (Vp, Vs) and density curves for saturated Sleipner-type sandstone rocks as a function of the CO2/brine fluid mixture, when the CO2 behaves as a dense supercritical “fluid” (at 37 o C, 10MPa) and as a light supercritical “gas” (at 44 o C, 7.5 MPa). In the supercritical “fluid” case, the bulk density of the saturated rock is a weak linear function of the CO2 saturation, and Vp is a nonlinear function showing a strong decrease for CO2 saturations up to about 30% but little or no change for larger CO2 saturations. In the supercritical “gas” case, the bulk density of the rock is a strong measurable and linear function of the CO2 saturation, and Vp is a nearly binary function showing a strong decrease for small amounts of CO2 < 5-10% but little or no change for larger CO2 saturations. In both supercritical cases, Vs is fairly insensitive to CO2 saturation. 3D models and seismic simulations We built a 3D earth model loosely based on Sleipner logs, rock and fluid properties, and geologic/seismic structure, as shown in Figure 3. We introduced porosity heterogeneity using spatial statistics from another reservoir to examine its effects on seismic imaging and inversion. We created three fluid and pressure distributions in the model: (i) brine only, i.e. before CO2 injection (T0), (ii) after limited injection has created one layer of CO2 just below the impermeable cap rock (T1), and (iii) after further injection has created two vertically stratified layers of CO2, one beneath the cap rock as in T1 but with stronger saturation, and a second weaker saturated layer trapped below a deeper shale (T2). We generated synthetic seismic shot-gather data sets for each of the three CO2 injection scenarios acquired along a 2D line through the 3D model, using a visco-elastic finite-difference (FD) algorithm running on our parallel cluster. Figure 3 shows the z-component data (mainly P-waves) and the x-component data (mainly S-waves) of the elastic wavefield for a single shot gather. Note that a single layer of CO2 (at T1) generates a complex coda of many strong events in the shot-gather difference data (T1-T0) of Figure 3! The wavefield differences are even more complex at T2 for two stratified layers of CO2, as we show in the presentation. Seismic imaging We performed industry-standard prestack depth migration velocity analysis and image processing of the data sets for all three scenarios. Aside from the changes in CO2 saturation and pressure in the geo-sequestration layers, these data sets are perfectly repeatable from a time-lapse perspective. Figure 4 shows the P-wave depth image before and after CO2 injection (T0 and T1), and the time-lapse image (T1-T0). Figure 5 shows a zoom of the time-lapse difference image (T1-T0) for P-waves (left), converted PS-waves (right) and a comparison to a real time-migrated Pwave difference image from Sleipner (center). Note that even with our best velocity analysis and depth imaging in

Fixing the Non-uniform Directionality of Seismic Daylight Interferometry May Be Crucial to Its Success

The seismic daylight interferometry method of replacing active sources with receivers that act as virtual sources has huge potential for seismic exploration. The potential is because receivers can be placed in many locations where it is impractical, environmentally harmful, dangerous, or expensive to place active sources. Yet, the public tests of seismic daylight interferometry to date show generally poor data quality. We argue that this poor data quality may well result from the non-uniform directionality of the incident seismic wavefield measured at the receiver that is to become the virtual source. We present a passive data example that demonstrates the non-uniformity.

A risk analysis spreadsheet for both time-lapse VSP and 4D seismic reservoir monitoring

Summary We have developed a risk analysis spreadsheet suitable for both time-lapse VSP and 4D seismic reservoir monitoring projects. It is an enhanced version of the risk spreadsheet by Lumley et al. (1997). The significant new parameters developed for this study include measures of vertical and lateral resolution, source and receiver repeatability, and image aperture area, relevant for both VSP and 3D seismic acquisition. A scoring system quantifies the risk measured in each new parameter. We then describe a detailed risk analysis of six reservoir scenarios suitable for time-lapse (TL) VSP monitoring using the new spreadsheet technique. The six scenarios include CO2 injection in land-based carbonate reservoirs, steam injection in land-based sand reservoirs, and waterflood in marine-based sand reservoirs – all focused on monitoring a 20’ thin target zone. The six scenarios are fully evaluated in terms of reservoir and seismic parameters, and cross-plotted in a final combined analysis of all parameters. The results show that TL-VSP has the potential to be much lower risk than 4D seismic for all six scenarios, provided that TL-VSP surveys are highly repeatable, and attain excellent frequency content, areal coverage and image quality. The results also show that the best candidates for successful field tests of TL-VSP technology are steam injection projects in shallow soft sand reservoirs, and water-drive projects in soft sand reservoirs with high-GOR oils.

Ambient seismic field in three dimensions

We set out a seismic array containing over 4000 geophones over a 1500 foot square area to record the ambient wavefield. Direction of arrival estimation methods such as beam steering reveal a significant amount of coherent energy, with both low apparent velocities, indicating propagation along or near the surface, and very high apparent velocities, indicating near-vertical incidence. Nearby cultural noise sources such as a freeway account for the former, while the origin of the latter has not been determined. But the rate at which such near-vertically incident events were observed (about one every two seconds) is a surprising result.

3-D Prestack Depth Migration On Real Data

To get a good image of a complex subsurface, the geophysicist has to move from after stack to prestack migration, from time migration to depth migration and from 2D towards 3D processing. A 3D prestack depth migration program has been developed for migrating shot gathers. The program works in the frequency-space domain and currently uses a 45” algorithm with horizontal splitting to extrapolate in 3D. Some improvements have been implemented to save computation time and computer memory (interpolating the wavefield with a little depth step inside a large extrapolation step, packing the velocity model). 3D synthetic data and 2D real marine data presenting a large feathering have been migrated in this way. The results are satisfactory but the CPU time remains long. In order to improve the computation timeas well as the quality of the results, some algorithmic optimisations (solving the complete extrapolator by iterative methods or encoding the data) have been tested.