Integrated log interpretation in the German Continental Deep Drilling Program: Lithology, porosity, and fracture zones

Abstract

Abstract. Well logs, aquired in the two scientific drill holes of the German Continental Deep Drilling Program (KTB), provide continuous records of physical and chemical data of the metamorphic rocks penetrated. The 4-km-deep pilot hole was almost completely cored, enabling the well logs to be calibrated with regard to rock composition and structural features derived from laboratory analysis of cores. The observed relationships were transferred to the 9101 m deep, nearly uncored, main hole to reproduce in detail the lithology and to estimate physical properties from the logs. Synthetic lithological profiles were constructed for the pilot hole and the main hole by applying the electrofacies concept adapted to the crystalline environment. These profiles provide information on lithostratigraphy, alteration, cataclastic overprint, and petrogenetic features. Cross-hole correlations of these profiles reveal identical rock sequences for large sections of the drilled, metamorphic basement in both holes, in which the primary differences between the protoliths are largely preserved. Multivariate statistical methods were used to determine porosity depth functions from log responses. Linear as well as multilinear regression yielded continuous porosity profiles for both boreholes. Factor analysis was used to extract a parameter interpreted as a fluid and fracture indicator. Comparison of the porosity profiles with lithological information from log, core, and cuttings data revealed two different origins of increased porosity. Rock porosity and permeability are not only related to discrete planar discontinuities such as faults and fractures but also to more extensive zones of intense rock alteration where considerable matrix porosity occurs.

Well logging responses of UHP metamorphic rocks from CCSD main hole in Sulu terrane, eastern central China

“…Therefore, well logging plays a key role in scientific drilling project. It provides valuable information that could be used to study: (1) the orientation and magnitude of in-situ stress of the crust (Lund and Zoback, 1999;Brudy and Zoback, 1993); (2) the structure, composition, physical and chemical properties of the crust (Papasikas and Juhlin, 1997;Pechnig et al, 1997); (3) paleoclimate (Demezhko and Shchapov, 2001); (4) core orientation; and (5) deep crustal fluids (ELEKTB Group, 1997).…”

A Hybrid Monte Carlo Method Based Artificial Neural Networks Approach for Rock Boundaries Identification: A Case Study from the KTB Bore Hole

“…The rocks types mainly comprised of three main facies units: paragneisses, metabasites and alternations of gneiss-amphibolites, with a minor occurrence of marbles, calcsilicates, orthogeneisses, lamprophyres and diorites. Franconian Lineament, a thrust fault marking the boundary between the crystalline outcrop of the Bohemian Massif and the Permo-Mesozoic cover of southeast Germany, is situated to the west of the KTB drill hole (PECHNIG et al, 1997). The lithologic and metamorphic characteristics, especially the abundant metabasites and the medium pressure metamorphism, suggest that the Zone of Erbendorf-Vohenstrauss (ZEV) is a part of the Bohemiam (FRANKE, 1989) (Figs.…”

“…The stretching lineation is well developed in equigranular, fine-grained, high temperature mylionite, amphibolites and paragneisses. Along the boundary of the Zone of Erbendorf-Vohenstrauss (ZEV) with the surrounding imbrication zone are amphibolites of oceanic affinity and isolated bodies of serpentinites (BERCKHEMER et al, 1997;EMMERMANN and LAUTERJUNG, 1997;PECHNIG et al, 1997;KUMPEL, 1998, 1999). The detailed information about the Vol.…”

“…The detailed information about the Vol. 166,2009 KTB data and its geophysical significance can be found in several earlier papers (BERCKHEMER et al, 1997;PECHNIG et al, 1997;EMMERMANN and LAUTERJUNG, 1997;KUMPEL, 1998, 1999). We study here three types of well log data (viz.…”

“…Such well log data have been extensively used for exploration of oil and gas, mineral mining, geothermal energy and, radio-active waste deposits (PECHNIG et al, 1997). It is known that compositional and textural…”