The rapid rotation of Mars creates a significant pseudoforce, known as the Coriolis force, that greatly modifies the flight paths and subsequent deposition of distal ejecta (ejecta with launch velocities of 3 km/s and greater). An accurate depiction of the effects of the Coriolis force requires the integration of the Coriolis terms directly into a series of spherical ballistic equations applied within a rotating reference frame. The resulting landing positions of radially ejected particles tend to form distinct wrapping patterns that are focused to specific areas in the hemisphere opposite from the source crater: around the pole for high‐latitude craters (45° in latitude and above) and in an equatorial band for low‐latitude craters (below 45° latitude). Consequently, particular locations on the surface receive deposits in stages: direct delivery of ejecta followed by deposits of higher‐velocity ejecta. This staged deposition leads to regions of enhanced ejecta accumulations where meters of material collect (millimeters would be predicted in nonrotational radial decay models). Thus high‐latitude craters could supply a considerable amount of distal products (tektites and melts) to polar locations, perhaps contributing to the dark circumpolar materials.
Highly oblique impacts represent a rare and special class of impact events manifested as elliptical craters preserved on present‐day planetary surfaces. Crater excavation in highly oblique impacts differs from that of standard vertical impacts due to early time asymmetries imparted by the downrange‐directed coupling of energy between the projectile and target. Such asymmetries are preserved as scouring and mobilized surface materials produced by high‐velocity, low‐angle ejecta and blast winds along the initial impact trajectory axis downrange. Subsequent deposition of resulting melt‐rich products occurs in the form of concentrated strewnfields located downrange from the impact. The distinct nature of these distal strewnfields is separate from later time, more proximal ejecta accumulations and generally allows connecting these specific deposits with their parent crater. The present study involves a three‐dimensional computational impact simulation (modeled using the CTH shock physics hydrocode) of an event similar to the impact that produced the elliptical Hale impact crater on Mars (125 km × 150 km diameter crater located at 36°S, 36°W). Results generally capture the predicted patterns indicative of highly oblique impacts. Evidence is presented for correlated distal strewnfields located downrange from Hale that coincide with prominent low‐albedo surface deposits and wind streaks on the present‐day Martian surface, thereby providing implications for possible identification for other dark glassy strewnfields as well as impact‐generated winds on Mars.
Following the 2012 SEG Annual Meeting in Las Vegas, the SEG Research Committee sponsored a post-convention research workshop on subsea technologies, in general, and on seafloor characterization in particular. The goal of the workshop was to share experiences in acquisition, processing and applications of geotechnical and geophysical measurements for seafloor property characterization. This includes: To help geophysicists in better understanding geotechnical seafloor measurements, e.g., when and how they are collected as well as their actual field applications; To help geotechnical specialists in better understanding geophysical seafloor measurements, how they are derived, and their importance for accurate seismic waveform modeling and inversion; To discuss technology and application trends, and how the geophysical community can participate in the fast-growing market for subsea operations in the oil and gas industry.
Abstract— Although tenuous, the atmosphere of Mars affects the evolution of impact‐generated vapor. Early‐time vapor from a vertical impact expands symmetrically, directly transferring a small percentage of the initial kinetic energy of impact to the atmosphere. This energy, in turn, induces a hemispherical shock wave that propagates outward as an intense airblast (due to high‐speed expansion of vapor) followed by a thermal pulse of extreme atmospheric temperatures (from thermal energy of expansion). This study models the atmospheric response to such early‐time energy coupling using the CTH hydrocode written at Sandia National Laboratories. Results show that the surface surrounding a 10 km diameter crater (6 km “apparent” diameter) on Mars will be subjected to intense winds (˜200 m/s) and extreme atmospheric temperatures. These elevated temperatures are sufficient to melt subsurface volatiles at a depth of several centimeters for an ice‐rich substrate. Ensuing surface signatures extend to distal locations (˜4 apparent crater diameters for a case of 0.1% energy coupling) and include striations, thermally armored surfaces, and/or ejecta pedestals—all of which are exhibited surrounding the freshest high‐latitude craters on Mars. The combined effects of the atmospheric blast and thermal pulse, resulting in the generation of a crater‐centered erosion‐resistant armored surface, thus provide a new, very plausible formation model for high‐latitude Martian pedestal craters.
4D Seismic in Carbonates: From Rock Physics to Field Examples Ganglin Chen; Ganglin Chen Search for other works by this author on: This Site Google Scholar Kelly Wrobel; Kelly Wrobel ExxonMobil Upstream Research Company Search for other works by this author on: This Site Google Scholar Anupam Tiwari; Anupam Tiwari ExxonMobil Upstream Research Co. Search for other works by this author on: This Site Google Scholar Jie Zhang; Jie Zhang ExxonMobil Upstream Research Company Search for other works by this author on: This Site Google Scholar Michael Payne; Michael Payne ExxonMobil Upstream Research Company Search for other works by this author on: This Site Google Scholar William L. Soroka; William L. Soroka Abu Dhabi Co. Onshore Oil Opn. Search for other works by this author on: This Site Google Scholar Mohamed T. Hadidi; Mohamed T. Hadidi ADCO Search for other works by this author on: This Site Google Scholar Akmal Awais Sultan Akmal Awais Sultan Zakum Development Co. Search for other works by this author on: This Site Google Scholar Paper presented at the International Petroleum Technology Conference, Kuala Lumpur, Malaysia, December 2008. Paper Number: IPTC-12065-MS https://doi.org/10.2523/IPTC-12065-MS Published: December 03 2008 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Get Permissions Search Site Citation Chen, Ganglin, Wrobel, Kelly, Tiwari, Anupam, Zhang, Jie, Payne, Michael, Soroka, William L., Hadidi, Mohamed T., and Akmal Awais Sultan. "4D Seismic in Carbonates: From Rock Physics to Field Examples." Paper presented at the International Petroleum Technology Conference, Kuala Lumpur, Malaysia, December 2008. doi: https://doi.org/10.2523/IPTC-12065-MS Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex Search nav search search input Search input auto suggest search filter All ContentAll ProceedingsInternational Petroleum Technology ConferenceIPTC International Petroleum Technology Conference Search Advanced Search AbstractWe have carried out 4D seismic research on two giant carbonate fields in Abu Dhabi, UAE, employing an integrated approach. Our work process started from fundamental rock physics analysis. The Xu-White rock physics model, originally designed for clastic rocks, was extended to carbonates. With this model, we characterized the reservoir interval by different (geophysical) pore types, related them to petrophysical (sedimentalogical) pore types, and performed log conditioning to improve well to seismic ties. Laboratory ultrasonic measurements of core plugs and log analysis were conducted in combination with the rock physics model to examine the fluid and pressure sensitivities.Results from rock physics analysis were used to build thickness variation (wedge) models and saturation variation models based on realistic reservoir conditions. Systematic synthetic seismic modeling was carried out. To compare with the field seismic data, we performed 3D synthetic seismic modeling, using horizons picked on the field seismic to define the input layering model. The rock properties of the reservoir layers were computed from saturation and pressure changes obtained from the reservoir simulation model using rock physics transforms.We refined the seismic processing sequence to enhance the 4D signals of the field seismic data. Our preliminary results show clear higher 4D seismic amplitude patterns in the crest of the structure. We will invert the data for seismic impedance to compare with the impedance volume from synthetic seismic modeling based on the reservoir simulation model. The results from 4D seismic will be used to update the reservoir and simulation models for optimal history match.IntroductionHydrocarbon production from carbonate fields constitutes a significant portion of total global energy supply. While 4D seismic data has been very successful in monitoring hydrocarbon production from clastic reservoirs (e.g., Gouveia et al., 2004; Calvert, 2005; Boutte, 2007), there is still no consensus on its applicability to carbonate fields. The main difficulty is the well-known fact that the acoustic velocities of carbonates are insensitive to saturation and pressure changes, relative to the clastics (e.g., Wang 2001). Figure 1 shows ultrasonic measurement data on two typical reservoir carbonate cores from one of the carbonate fields in Abu Dhabi, UAE. Figure 1a shows the pressure dependence of the compressional wave velocity of a dry sample. Under reservoir pressure conditions (3000 - 4000 psi), a pressure change of 500 psi changes the velocity by about 2%. In contrast, for unconsolidated sand-clay mixture samples of similar porosity (~20%) under similar pressure conditions, a change of 500 psi in the confining pressure induces about 6% change (three times of the carbonate sample) in the compressional wave velocity (Marion et al., 2001). The change in the P-wave velocity in the carbonate sample shown in Figure 1b is even more dismal until water saturation change reaches 90%. Keywords: Upstream Oil & Gas, saturation change, seismic data, reservoir simulation model, Reservoir Characterization, simulation model, porosity, Modeling & Simulation, pressure change, migration Subjects: Reservoir Characterization, Seismic processing and interpretation This content is only available via PDF. 2008. 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Following the 2012 SEG Annual Meeting in Las Vegas, the SEG Research Committee sponsored a post-convention research workshop on subsea technologies, in general, and on seafloor characterization in particular. The goal of the workshop was to share experiences in acquisition, processing and applications of geotechnical and geophysical measurements for seafloor property characterization. This includes: To help geophysicists in better understanding geotechnical seafloor measurements, e.g., when and how they are collected as well as their actual field applications; To help geotechnical specialists in better understanding geophysical seafloor measurements, how they are derived, and their importance for accurate seismic waveform modeling and inversion; To discuss technology and application trends, and how the geophysical community can participate in the fast-growing market for subsea operations in the oil and gas industry.
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