The appraisal of surface orbital vibrators with buried geophone array for permanent reservoir monitoring

Time-lapse seismic is one of the main methods for monitoring changes in reservoir conditions caused by production or injection of fluids. One approach to time-lapse seismic is through permanent reservoir monitoring, whereby seismic sources and/or receivers are permanently deployed. Permanent reservoir monitoring can offer a more cost-effective and environmentally friendly solution than traditional campaign-based surveys that rely on temporarily deployed equipment while facilitating more frequent measurements. At the CO2CRC Otway Project, surface orbital vibrators were coupled to a buried geophone array to form a permanent reservoir monitoring system. These are fixed position seismic sources that provide both P and S waves using induction motor-driven eccentric masses. After an initial injection of CO₂ in February 2016, five months of continuous seismic data were acquired, and reflection imaging was used to assess the system performance. Analysis of the data showed the effects of weather variations on the near-surface conditions and the sweep signatures of surface orbital vibrators. Data processing flows of the continuous data was adapted from Vibroseis four-dimensional data processing flows. Ground roll proved a significant challenge to data processing. In addition, variations in the surface wave pattern were linked to major rainfall events. For the appraisal of surface orbital vibrators in imaging, a Vibroseis four-dimensional monitor survey data with similar geometry was also processed. Surface orbital vibrators are observed to be reliable sources with a potential to provide a repeatable signal, especially if the ground roll should fall outside the target window of interest. To guide future permanent reservoir monitoring applications, a repeatability analysis was performed for the various key data processing steps.     

Solar Sources of Interplanetary Coronal Mass Ejections During the Solar Cycle 23/24 Minimum

We examine solar sources for 20 interplanetary coronal mass ejections (ICMEs) observed in 2009 in the near-Earth solar wind. We performed a detailed analysis of coronagraph and extreme ultraviolet (EUV) observations from the Solar Terrestrial Relations Observatory (STEREO) and Solar and Heliospheric Observatory (SOHO). Our study shows that the coronagraph observations from viewpoints away from the Sun–Earth line are paramount to locate the solar sources of Earth-bound ICMEs during solar minimum. SOHO/LASCO detected only six CMEs in our sample, and only one of these CMEs was wider than 120^°. This demonstrates that observing a full or partial halo CME is not necessary to observe the ICME arrival. Although the two STEREO spacecraft had the best possible configuration for observing Earth-bound CMEs in 2009, we failed to find the associated CME for four ICMEs, and identifying the correct CME was not straightforward even for some clear ICMEs. Ten out of 16 (63 %) of the associated CMEs in our study were “stealth” CMEs, i.e. no obvious EUV on-disk activity was associated with them. Most of our stealth CMEs also lacked on-limb EUV signatures. We found that stealth CMEs generally lack the leading bright front in coronagraph images. This is in accordance with previous studies that argued that stealth CMEs form more slowly and at higher coronal altitudes than non-stealth CMEs. We suggest that at solar minimum the slow-rising CMEs do not draw enough coronal plasma around them. These CMEs are hence difficult to discern in the coronagraphic data, even when viewed close to the plane of the sky. The weak ICMEs in our study were related to both intrinsically narrow CMEs and the non-central encounters of larger CMEs. We also demonstrate that narrow CMEs (angular widths ≤?20^°) can arrive at Earth and that an unstructured CME may result in a flux rope-type ICME.     

Successive regressions and transgressions in the Neogene

The observations reported here were made over a period of twenty-two months encompassing six field seasons. the present study demonstrates the highly variable nature of sedimentary processes during different seasons of the year and sometimes from year to year in an area characterized by two different monsoonal phases. Depositional processes characterize one monsoonal phase and erosional processes dominate the other. Lond-term environmental monitoring of sedimentary processes is especially appropriate when extending acceptable uniformitarian criteria to the study of ancient sediments. Conclusions made from short-term studies can give an erroneous view as to the overall nature of sedimentary processes in these areas.     

Characterization of the Rapanui mass-transport deposit and the basal shear zone: Mount Messenger Formation,Taranaki Basin,New Zealand

Submarine mass-transport deposits are important in many ancient and modern basins. Mass-transport deposits can play a significant role in exploration as reservoir, seal or source units. Although seismic data has advanced the knowledge about these deposits, more outcrop studies are needed to better understand gravity mass flows and predict the properties of their resultant deposits. It is proposed that sufficiently well-exposed outcrops of mass-transport deposits can be divided into three strain-dominant morphodomains: headwall, translational and toe. The outcrops of the Rapanui mass-transport deposit, part of the Lower Mount Messenger Formation in the Taranaki Basin, New Zealand, are exposed along a ca 4 km transect in coastal cliffs that enable the identification of the three morphodomains. The aim of this study is to characterize the stratigraphic and sedimentological nature of the Miocene-age Rapanui mass-transport deposit outcrops and the evolution of its basal shear zone. The basal shear zone of a mass-transport deposit is defined as the stratal zone formed in the interface between the overriding mass flow and the underlying in situ deposits or sea floor. Accordingly, the deformation structures in the Rapanui mass-transport deposit and the basal shear zone were documented in an established spatial framework. Traditional methodologies were used to characterize the sedimentology of the Rapanui mass-transport deposit. Data collected from intrafolial folds, rafted blocks and samples from the Rapanui mass-transport deposit were used to investigate strain and matrix texture evolution, estimate palaeoflow direction, and calculate yield strength and overpressure at time of deposition. Additionally, a one-dimensional numerical model was used to test sedimentation-driven overpressure as probable trigger. This work demonstrates that the basal shear zone, as well as the matrix texture of a mass-transport deposit, can vary spatially as sediments from underlying deposits are entrained during shear-derived mixing. This phenomenon can impact the seal potential of mass-transport deposits and their interaction with fluids in the subsurface.     

ANN-Based Prediction of Laboratory-Scale Performance of CO2-Foam Flooding for Improving Oil Recovery

Natural Resources Research - Improving oil recovery by CO2 injection continues to gain momentum in mature oil fields due to its favorable industrial and environmental benefits. One remediation for...     

Sedimentation,cleavage and tectonic thinning in the aberystwyth grits between clarach and wallog,cardigan bay

In recent years the folding and cleavage seen in the Aberystwyth Grits has been ascribed to downslope movement in soft unlithified sediment, not to tectonic forces. A detailed examination of folded beds in a small part of the outcrop was undertaken to test this theory. It is concluded that the folding and cleavage was initiated by movement from a rising tectonic ridge, but that the sediments may not have been completely lithified at the time of folding.     

The Low Inclination Dwarf Nova UY PUP

A spectroscopic study of the frequently outbursting dwarf nova UY Pup has been undertaken whilst the system was in outburst. The Hα andHβ line profiles in UY Pup are typical of low inclination dwarf novae after outburst maximum. No evidence for two components is seen in the emission lines. Using radial velocity measurements of Hα, we find the best fit orbital period for the system to be 10.22 ± 0.19 h(although we cannot with certainty rule out a period of 7.13 ± 0.14 h).We place limits on the system parameters. We also present multicolour photometry of UY Pup in quiescence. This revised version was published online in July 2006 with corrections to the Cover Date.