Hans-Joachim Kümpel

Fractal variability in superdeep borehole — implications for the signature of crustal heterogeneities

Abstract The deep and superdeep boreholes of the German Continental Deep Drilling Program (KTB) provide probably the most extensive data archive on in-situ properties of metamorphic crustal rock from a single site. Analysis of the variability of several geophysical parameters point out fractal features and a degree of correlation between data values comparable to 1/ f -noise. Accordingly, the Earths crust, at the KTB site, can be statistically described as an inhomogeneous medium whose properties are basically invariant from metre to kilometre scale. Piecewise homogeneous models appear to be inadequate to represent petrophysical properties, at least in the vertical dimension, and 1/ f -noise offers a far more suitable concept to simulate heterogeneities in the Earths crust.

In-Situ Petrohydraulic Parameters from Tidal and Barometric Analysis of Fluid Level Variations in Deep Wells: Some Results From KTB

Natural fluid level fluctuations in sufficiently deep wells reflect pore pressure variations of the hydraulically connected formations, that are e. g. caused by tidal strain, changes in barometric pressure, or the passage of seismic wave fields. From comparison of the fluid level variations with the source signal in-situ petrohydraulic rock properties may be derived. Aiming to improve our knowledge about the petrohydraulic conditions and the volume strain spectrum in the intermediate crust, quasi continuous, high resolution fluid level registrations are carried out at the KTB (super-) deep boreholes in Bavaria, Germany, since summer 1996. The fluid level of the 4 km deep pilot hole shows a clear tidal signal with peak to peak amplitudes of 13 cm and a static confined barometric efficiency of about 60 to 65%. Adopting poroelastic rheology, the areal strain sensitivity was found to be 0.16 hPa/n∈ (M2) and 0.19 hPa/n∈ (O1), which is consistent with a Skempton ratio B of roughly 0.40 to 0.45, respectively, when adopting a drained Poisson ratio ν of 0.24. The fluid level of the main hole (9.1 km deep) does not present any tidal or barometric signals, most likely because of some obstruction at depth, but yet shows a monotonous lowering.

Conference addresses thermo‐hydro‐mechanical coupling in fractured rock

Various environmental problems and the use of certain energy resources are closely related to fluid flow in and the mechanical behavior of porous or fractured rock. Subjects of obvious socioeconomic relevance are the supply and protection of groundwater, the production of hydrocarbon reservoirs, land subsidence in coastal areas, exploitation of geothermal energy and the long-term disposal of critical wastes. Efficient management of such issues is often hampered by the fact that rocks and rock formations are inherently complex. Any rock sample is an aggregate of the myriad mineral particles forming its matrix and fluid molecules residing in voids. Any two rock samples differ in many aspects, including geochemical constituents, size and shape of grains, structure of pore space, and fracture networks.

Scale Aspects of Geo-Data Sampling

Sampling data values in earth sciences is all but trivial. The reason is the multi-scale variability of observables in nature, both in space and in time. Sampling geo-data means selecting a finite number of data points from a continuum of high complexity, or from a system of virtually infinite degree of freedom. When taking a reading a filtering process is automatically involved, whatever tool or instrument is used. The design of adequate sampling strategy as well as proper interpretation of geo-data thus requires a-priori insight into the variability of the target structure and/or into the dynamics of a time varying observable. Ignoring the inherent complexity of earth systems can ultimately lead to grossly false conclusions. Retrieving data from nature and deducing meaningful results obviously is an expert’s task.

Search for strange attractors in magnetic field data: An example from a tertiary volcanic area near Bonn, Germany

Abstract Spatial variations of the magnetic field, measured at the Earths surface, are mainly due to geological inhomogeneities within the crust. The present state of the crust, in turn, reflects its past dynamical processes and evolution. We analyzed the magnetic field intensity along a few but densely sampled profiles in a Tertiary volcanic province near Bonn, Germany. The aim was to find out whether the variation of the magnetic intensity can be related to a deterministic, although chaotic, generating system or to a stochastic one. In the former case, the geodynamical history would depend on a few degrees of freedom, whereas in the latter case, the parameters to take into account were so many that a statistic approach appears to be more suitable. Since strange attractors do not emerge from the analyzed data, we exclude the presence of a chaos generating system. Autocorrelation functions and a rescaled-range analysis, on the other hand, reveal and quantify a certain degree of correlation among successive data points and allow calculation of a range of spectral exponents in log-log diagrams, which are clearly distinct from those of white noise and Brownian motion. Only one of the profiles exhibits similarity to uncorrelated or white noise. In this case, the signal variations do not result from the local geology but from a buried gas pipe-line, aligned subparallel to that profile. If self-organized crustal evolution generally produces signatures that can be described as correlated noise, within a limited bandwidth of spectral exponents, erraneous or disturbed data could eventually be discriminated from records containing purely natural data by applying analysis tools of the dynamic system theory together with autocorrelation tests.

Zwölfstündige Wasserstandsvorhersage in der Deutschen Bucht—Untersuchungen zur Online-Vorhersagequalität

Fur ein von Kumpel und Zschau [1986] vorgeschlagenes Modell zur mittelfristigen Wasserstandsvorhersage wurden von Goltz [1990] die hard- und softwaremasigen Voraussetzungen fur zwolfstundige Vorhersagen im Echtzeitbetrieb geschaffen.