Geobody architecture, genesis and petrophysical characteristics of the Budakalász travertines, Buda Hills (Hungary)

Abstract

19Pre-salt reservoir systems encountered offshore Brazil and Angola that consist of porous continental 20 carbonates are difficult to access because of the limited core material that is under concession. 21 Therefore, it is important to study comparable continental carbonate analogues, like travertines and 22 lacustrine carbonates, that possess similar porosity and permeability characteristics. The Budakalász 23Pleistocene travertines (Buda Hills, Hungary) have been studied from a sedimentological, geochemical 24 and reservoir point of view in order to understand their formation, petrophysical properties and 3D 25 reservoir architecture. 26The three-dimensional geobody architecture of the Budakalász travertines illustrates the potential 27 complexity of kilometre scale continental carbonate systems. Heterogeneous smooth sloping travertine 28 lobes consisting of terrace slope, smooth slope and reed facies, are covered by a lime mudstone 29 dominated, gastropod-and charophyte-rich marsh-pool facies. The observed facies represent a change 30 from a subaerial travertine to a palustrine to lacustrine system, reflecting the ceasing of the system due 31 to tectonic uplift. The dominant paleo-flow direction of the sloping lobes was towards the Danube 32 depression, with several subordinate flow systems identified. 33The Sr-C-O isotope geochemical signatures reflect travertine precipitation at ambient to superambient 34 temperatures from meteoric derived fluids with a mixed CO2 origin of the marine carbonate fluid 35 source rocks and an atmospheric or soil-derived component. Although the uniform signatures of the 36 stable oxygen and carbon isotopes, in addition to petrographic observations suggest partial diagenetic 37 isotopic resetting, the primary geospatial isotope trends seem to have been preserved. 38 2 A reservoir-oriented facies evaluation in the three-dimensional geobody frame of the Budakalász 39 carbonates based on porosity and permeability core plug analyses reveals their heterogeneous nature. 40Terrace, smooth slope and marsh-pool facies have considerable porosities of 5-15%, while the 41 porosity of the reed facies may reach up to 27%. Permeability of all facies is strongly anisotropic, 42 mainly controlled by a better connectivity along layer-parallel primary pores. 43The reconstruction of the 3D geobody architecture of the Budakalász lobe complex coupled to its 44 geochemical and petrophysical properties provides a unique dataset that so far was lacking. 45 46

Lattice Boltzmann Simulations of Fluid Flow in Continental Carbonate Reservoir Rocks and in Upscaled Rock Models Generated with Multiple-Point Geostatistics

“…All of these facies types have pores at least varying from nanometer to centimeter scale and could have relevant contributions to fluid flow in this material. For a sedimentological background of the samples (out of the scope of this study), the reader is referred to earlier published literature [1,14,41,42].…”

“…Quantitative data about lithofacies' occurrence, distributions, and their related porosity and permeability are key to understanding the reservoir behavior. The sedimentology of continental carbonates has been widely studied [7][8][9][10][11][12][13], but recently the focus of continental carbonate studies shifted towards the rocks' petrophysical properties like porosity, permeability, and acoustic velocities [14][15][16][17][18][19][20][21][22]. Noteworthy is the fact that the permeability inside rocks is strongly dependent on the geometric and topological properties of the porous medium at microscopic scales [23].…”

Comment on “First records of syn-diagenetic non-tectonic folding in Quaternary thermogene travertines caused by hydrothermal incremental veining” by Billi et al. Tectonophysics 700–701 (2017) 60–79

“…Furthermore, the maximum thickness of travertine in slope environments does not exceed a few tens of meters as found in several areas worldwide (Pentecost 1995;Guo et al, 1996;Hancock et al, 1999;Brogi, 2004;Brogi et al, 2010;Ronchi and Cruciani, 2015;Khatib et al 2014;Lebatard et al, 2014;Claes et al, 2017). This implies that travertine can only be affected by deformation at, or near the surface.…”

“…2). This is well constrained by threedimensional observations in most active and fossil travertine (and tufa) depositional systems (Italy: Chafetz and Folk, 1984;Guo and Riding, 1998;D'Argenio et al, 1981, D'Argenio and Ferreri, 1987,1988Hungary: Scheuer and Schweitzer, 1981;Kele et al, 2008;Claes et al, 2017 Turkey: Altunel and Hancock, 1993a;1993b;Khatib et al 2014;Lebatard et al, 2014;Claes et al, 2015;Tunisia: Henchiri et al, 2017; China: Liu et al,…”

A new methodology to train fracture network simulation using multiple-point statistics

“…In this study, UAV-based photogrammetry is used to obtain an orthorectified mosaic and 3-D digital outcrops models (Bemis et al, 2014;Claes et al, 2017;Vollgger and Cruden, 2016). The scale of these images is an intermediate between the scale of the measurement station and that of the satellite imagery.…”