Abnormal Pressure and Hydrocarbon Migration in the Békés Basin

Permeability and Mineralogy of the Újfalu Formation, Hungary, from Production Tests and Experimental Rock Characterization: Implications for Geothermal Heat Projects

“…The permeability values that we have derived from the production tests of wells T-1 and VS-1 at Mezőberény, 18 to 278 mD (Table 1), are low compared to regional averages published in 1994 by Spencer et al [11], ~70 to ~400 mD (Figure 16). Nonetheless, because Spencer et al [11] only published average permeability values, it is unclear if our dataset is statistically different from theirs. We have no access to the raw data underlying their study but suggest possible reasons for this difference in results.…”

“…For comparison, Spencer et al [11] reported ~100 to ~400 mD in the horizontal direction and ~70 to ~300 mD in the vertical direction (Figure 16). It is thus evident that Spencer et al [11] regarded this formation as more permeable in the horizontal direction whereas our results indicate greater vertical permeability. However, for both sets of measurements, the difference between horizontal and vertical permeability is small compared with the range of values measured in either direction.…”

“…The apparent higher permeability perpendicular to the bedding might be a real feature of the core from the Gyoma-1 well, conceivably through diagenesis, but might potentially instead have arisen from the image processing workflow in which the initial suite of two-dimensional X-ray projections has been reconstructed into a three-dimensional volume, then transformed into a series of slices in planes perpendicular to the z-axis (Figure 4); the Spencer et al [11] and Almási [23] datasets favour the latter interpretation. Furthermore, the wider range in permeabilities from the flow modelling could be because of the smaller volumes analyzed compared to Spencer et al [11], which makes it possible to capture high porosity and low porosity sub-volumes separately from each other, whereas in a core-scale experiment these would average out. Indeed, if we were to restrict the permeability analysis to the Kozeny-Carmen fits through the core-averaged porosity of 0.18 (Figure 15), the resulting permeabilities are much more similar to those determined by Spencer et al [11].…”

“…(formerly known as the Törtel Fm. [10]), and fluvial sandstones of the Zagyva Fm., which form both prolific hydrocarbon reservoirs and also geothermal resources [10][11][12][13]. Strictly speaking, these named 'formations' are lithofacies associations with diachronous boundaries [14], hence the 'interleaved' boundaries in Figure 1.…”

“…One of few recently published studies, by Varga et al [22], on reservoir properties of Pannonian sandstone, provides a qualitative evaluation of scaling and cementation for a geothermal site at Szeged (Figure 1). In contrast, one of the most recent publications to quantify porosity and permeability of Pannonian sandstones dates from 1994 [11]. Istan Almási's Ph.D. thesis, examined in 2001 [23], which reports analyses of 12,899 core samples from 689 petroleum wells in Hungary, is widely cited as a source of information on hydraulic properties of geothermal reservoir rocks.…”