Precise temperature monitoring in boreholes: evidence for oscillatory convection? Part 1: Experiments and field data

Temperature was monitored in two boreholes in Kamchatka (Russia) in years 2001–2003. Ten-min reading (sampling) interval was selected for the first half-year run followed by shorter (12 days) experiment with 5-s reading interval. A similar experiment was repeated later in the test borehole Sporilov (Prague, Czech Republic), where four temperature–time series were performed with reading intervals varying from 1 to 20 s. All temperature–time series (except the record from the bottom of the hole) displayed intermittent, non-periodic oscillations of temperature of up to several hundredths of degree with sharp gradients and large fluctuations over all observed time intervals. No such oscillation was detected at the bottom of the hole. The spectral analysis revealed a high level of stochasticity in the measured signal. Calculated spectra showed “band-pass” behavior without any definite peaks, which might characterize certain periodicity. Local growth of the second moment technique revealed the presence of at least two distinct temperature-forming processes. One of them can be related to heat transfer in the structurally and compositionally complex subsurface. The second process, which presents the bulk of the measured signal, probably reflects certain intra-hole convection. We hypothesized that the oscillatory regime of such convection is responsible for the stochastic nature of measured temperatures. Results of numerical modeling describing the fluctuation of water-cells in a vertical slot support the idea of thermally unstable water column in a hole, the instability of which produces a complex oscillation system. Model solutions and their discussion is presented in Part II of this work.     

Can Distrust Enhance Public Engagement? Insights From a National Survey on Energy Issues in Canada

Research examining the relationship between trust, public engagement, and natural resource management asserts that trust fosters positive behavior and enhanced cooperation. Yet some scholars are finding that certain kinds of distrust are helpful in achieving democratic outcomes by providing would-be participants with the motivation to engage in issues of public concern. This article seeks to clarify this apparent disjuncture in the trust literature by examining the multidimensional nature of trust as it relates to public engagement on energy-related issues in Canada. Based on a national online survey (n?=?3000) we use a binary probit model to explore the connections between trust, knowledge, and public engagement. About 70% of respondents had participated in at least one form of public engagement over the last 3 years. Drawing on a two-dimensional conception of trust, we find that general trust on its own is not positively linked to public engagement. A combination of general trust and skepticism, however, is positively associated with public engagement and confirms our hypothesis that at least some concern regarding credibility, bias, and vested interest can motivate public engagement. In this sense, trust is not uniformly good for public engagement. These results signal a need to further refine our assumptions about the relationship between public trust, public engagement and environmental governance.     

An integrated model of clastic injectites and basin floor lobe complexes: implications for stratigraphic trap plays

Injectites sourced from base‐of‐slope and basin‐floor parent sandbodies are rarely reported in comparison to submarine slope channel systems. This study utilizes the well‐constrained palaeogeographic and stratigraphic context of three outcrop examples exposed in the Karoo Basin, South Africa, to examine the relationship between abrupt stratigraphic pinchouts in basin‐floor lobe complexes, and the presence, controls, and character of injectite architecture. Injectites in this palaeogeographic setting occur where there is: (i) sealing mudstone both above and below the parent sand to create initial overpressure; (ii) an abrupt pinchout of a basin‐floor lobe complex through steep confinement to promote compaction drive; (iii) clean, proximal sand beds aiding fluidization; and (iv) a sharp contact between parent sand and host lithology generating a source point for hydraulic fracture and resultant injection of sand. In all outcrop cases, dykes are orientated perpendicular to palaeoslope, and the injected sand propagated laterally beneath the parent sand, paralleling the base to extend beyond its pinchout. Understanding the mechanisms that determine and drive injection is important in improving the prediction of the location and character of clastic injectites in the subsurface. Here, we highlight the close association of basin‐floor stratigraphic traps and sub‐seismic clastic injectites, and present a model to explain the presence and morphology of injectites in these locations.     

Compositional flow modeling using a multi-point flux mixed finite element method

We present a general compositional formulation using multi-point flux mixed finite element (MFMFE) method on general hexahedral grids. The mixed finite element framework allows for local mass conservation, accurate flux approximation, and a more general treatment of boundary conditions. The multi-point flux inherent in MFMFE scheme allows the usage of a full permeability tensor. The proposed formulation is an extension of single and two-phase flow formulations presented by Wheeler and Yotov, SIAM J. Numer. Anal. 44(5), 2082–2106 (35) with similar convergence properties. Furthermore, the formulation allows for black oil, single-phase and multi-phase incompressible, slightly and fully compressible flow models utilizing the same design for different fluid systems. An accurate treatment of diffusive/dispersive fluxes owing to additional velocity degrees of freedom is also presented. The applications areas of interest include gas flooding, CO ₂ sequestration, contaminant removal, and groundwater remediation.     

Convergence of iterative coupling of geomechanics with flow in a fractured poroelastic medium

We consider an iterative scheme for solving a coupled geomechanics and flow problem in a fractured poroelastic medium. The fractures are treated as possibly non-planar interfaces. Our iterative scheme is an adaptation due to the presence of fractures of a classical fixed stress-splitting scheme. We prove that the iterative scheme is a contraction in an appropriate norm. Moreover, the solution converges to the unique weak solution of the coupled problem.     

Comparison of Fiberglass and Other Polymeric Well Casings, Part III. Sorption and Leaching of Trace-Level Metals

This series of experiments was initiated to determine the overall suitability of three alternative polymeric well casing materials (fluorinated ethylene propylene [FEP], fiberglass-reinforced epoxy [FRE], and fiberglass-reinforced plastic [FRP]) for use in ground water monitoring wells and to compare these materials with polyvinyl chloride (PVC) and polytetrafluoroethylene (PTFE) well casings. This paper focuses on sorption and leaching of metals.
Generally, the fiberglass materials leached more metal contaminants than PVC, FEP, and PTFE. However, with one exception (Pb leaching from FRP), leached concentrations were below maximum allowable limits set by the U.S. Environmental Protection Agency (EPA) for drinking water. With respect to sorption, none of the polymers sorbed the anions tested, but all of them sorbed one or more of the cations tested. FEP and PTFE were much less sorptive than the other materials.     

Ichnofabrics and geometric configurations of Ophiomorpha within a sequence stratigraphic framework: an example from the Upper Cretaceous US western interior

Ichnofabric in the Upper Cretaceous Sego Sandstone and Anchor Mine Tongue of east-central Utah can be differentiated into two components: (1) discrete Ophiomorpha and (2) mottling and other trace fossils. The ichnofabric index method was employed to evaluate spatial variability of the ichnofabrics within depositional sequences and component systems tracts. Indices were logged for amount of bioturbation caused solely by Ophiomorpha (Oii) and that represented by all other biogenic features (Bii). Values of Oii> 1 are more pervasive in lowstand systems tracts compared to transgressive systems tracts. This is consistent with the predominance of marginal and nearshore marine, sand-dominated settings that are characteristic of lowstands, which are favourable habitats for colonization by Ophiomorpha producers. Ichnofabric index values vary both vertically and laterally within any given systems tract, reflecting differences in physical and biological parameters operating in the palaeoenvironment. These parameters include the total number and behaviours of organisms occupying the substrate, as well as substrate texture and grain size, and rates of sedimentation. The architectural style of Ophiomorpha was examined within five depositional facies: shelf, storm deposit, lower shoreface, shoreface, and estuarine. Inclinations of individual burrow elements were approximated relative to bedding planes, categorized as either vertical, inclined or horizontal, and then plotted on ternary diagrams. Based on the types of facies present, these results suggest that variations in the geometric configurations of Ophiomorpha are controlled primarily by physical energy levels, and the rate and nature of sedimentation. Results of this study have broad implications for understanding the physical factors affecting facies variability within sequences and systems tracts. When coupled with sedimentologic data, recognition of variations in the distribution of ichnofabrics and architectural style of Ophiomorpha can provide additional information useful for characterizing depositional environments, and therefore could be integrated with other basin analysis techniques to test and refine sequence stratigraphic interpretations.     

Large,prehistoric clay slides revealed in road excavations in Buvika,mid-Norway

Several excavated sections along new roads in Buvika, mid-Norway, display records of large, prehistoric clay slides. Slightly undulating but otherwise intact laminated clay, with minor amounts of unsorted or sorted coarser-grained debris, appears in the sections. Folding, shearing and internal slide surfaces have also been recorded, and the deposits are interpreted as slide debris. Slide-scar morphologies are diffuse or absent for most of these deposits, and the inferred slide mechanism is translation and rotation of blocks on a thin layer of remoulded quick clay. One section cuts through a slide block inside a classic, morphologically well-defined quick-clay slide scar. Varying results from ¹⁴C-datings of organic material in the deposits give only maximum ages of the slide events. The style of sliding reflected in several sections differs from slide events in the area known from historical records. These younger slide events seem to be characterised by collapse and remoulding of thicker quick-clay layers. The present study of slide deposits gives information on processes and deformation history of the slides. It is suggested that the gradual formation of quick clay has an important impact on long-term landscape degradation and on the character of the present day landscape. There may be far more signs of slide activity in Norwegian valleys than solely indicated by slide scars and also in the relatively high-lying parts of the valley fill, such as interfluve areas.