BG Europe Updated 2026-08-20

Bulgaria Geothermal Screening

Geothermal screening assessment identifies 20.6% prospective land reaching 185°C by 5.5 km depth in Bulgaria.

Key Geothermal Metrics

Land Reaching 185°C by 5.5 km Moderate
20.6%

Primary baseline screening criterion

Shallowest Depth to 200°C Shallow
4.4 km

Minimum drill depth for high enthalpy

Peak Temperature at 5 km Depth Commercial EGS
221.7 °C

Maximum modeled temperature

Typical Geothermal Gradient Elevated
43.2 °C/km

Average to 5 km depth (15°C surface)

Grid Connectable Prospective Area High Accessibility
90.8%

Hot territory within 50 km transmission

Stored Heat In-Place (3–7 km) 1 ZJ = 10²¹ Joules
45.3 ZJ

Thermal volume in place (>80°C baseline)

Depth vs. Temperature Matrix (% Land Area)

Proportion of national territory exceeding target isotherm at specified depth

0.1° Inversion Grid
Isotherm 3.0 km 4.0 km 5.0 km 6.0 km 7.0 km 8.0 km
150°C 4.5% 9.7% 14.8% 21.6% 28.5% 34.8%
175°C 3.6% 8.3% 11.8% 16.2% 20% 23.1%
200°C 2.5% 6% 8.1% 12.9% 14.2% 19.3%
225°C 1.4% 3.6% 5.3% 8.3% 9.4% 12.4%
250°C 0.7% 1.5% 2.8% 3.8% 4.5% 5.8%

4-Stage Geothermal Resource & Infrastructure Funnel

Progressive screening from gross national territory down to grid-connected & populated prospective zones

1 Whole country
110 879 km² 100%
2 Reaches 185°C by 5.5 km
22 841 km² 20.6%
3 ...and within 50 km transmission
20 740 km² 18.7%
4 ...and within 100 km town
19 657 km² 17.1%

Geological Setting & Subsurface Parameters

Lithology, basement thickness, stress and thermal boundary constraints

Median Depth to 200°C Isotherm 7.3 km
Best 10th Percentile Depth to 200°C 5.2 km
Median Temperature at 5 km Depth 178.7 °C
Best 10th Percentile Temp at 5 km 201.6 °C
Median Sediment Thickness 2 km
Sediment / Hard-Rock Well Share 10.8%
Territory Under 1 km Sediment Cover 61.1%
Lithostatic Pressure at 5 km Depth 135 MPa
Moho Crustal Discontinuity Depth 35.1 km
Thermal Lithosphere Thickness 86.9 km
Curie Temperature Isotherm Depth 22.9 km
Model Temperature Spread Uncertainty (200°C) ±0.9 km

Transmission Grid & Demand Colocation

Infrastructure interconnectivity and urban power demand proximity

High-Voltage Transmission Network Length 6 455 km
Land Area Within 25 km of Grid 70.3%
Land Area Within 50 km of Grid 90.8%
Land Area Within 100 km of Grid 99.5%
Average Proximity to Nearest Substation / Line 14.6 km
Urban Centers (>10,000 Population) 45
Total Urban Population 8.7 M
Prospective Resource Colocated Near Demand (>1M Pop) 47.6%

Target Sensitivity & Deep EGS Upside

Sensitivity of prospective resource area to adjusted depth and temperature thresholds

150°C Baseline at 5.5 km 33% of national territory reaches 150°C at 5.5 km depth
185°C Baseline at 7.5 km 37.1% of national territory reaches 185°C at 7.5 km depth

Global Peer Benchmarking (vs. 278 Assessed Jurisdictions)

Relative ranking distribution of Bulgaria across 11 standardized geothermal indicators

Bulgaria Rank Global Peer Spread
Shallowest 200°C depth
4.4 km Middle 50%
P0 (Lowest) P50 (Median) P100 (Highest) • 51th percentile
Peak temp at 5 km
221.7 °C Lower 50%
P0 (Lowest) P50 (Median) P100 (Highest) • 49th percentile
Prospective land area (>185°C at 5.5 km)
20.6% Lower 50%
P0 (Lowest) P50 (Median) P100 (Highest) • 34th percentile
Stored heat in-place (3-7 km)
45.3 ZJ Middle 50%
P0 (Lowest) P50 (Median) P100 (Highest) • 52th percentile
Typical geothermal gradient
43.2 °C/km Middle 50%
P0 (Lowest) P50 (Median) P100 (Highest) • 62th percentile
Grid proximity (<50 km)
90.8% Top 10%
P0 (Lowest) P50 (Median) P100 (Highest) • 91th percentile
Thin sediment coverage (<1 km)
61.1% Middle 50%
P0 (Lowest) P50 (Median) P100 (Highest) • 61th percentile
Curie isotherm depth
22.9 km Lower 50%
P0 (Lowest) P50 (Median) P100 (Highest) • 50th percentile
Moho crustal thickness
35.1 km Lower 50%
P0 (Lowest) P50 (Median) P100 (Highest) • 37th percentile
Model temperature uncertainty spread
±1.5 km Middle 50%
P0 (Lowest) P50 (Median) P100 (Highest) • 55th percentile
Urban demand colocation
31.1% Top 25%
P0 (Lowest) P50 (Median) P100 (Highest) • 66th percentile
Asset-Level 3D Simulation Available

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Analytical Geothermal Assessment & Discussion: Bulgaria

Subsurface thermal interpretation, model uncertainty, infrastructure colocation, and resource quality analysis

Resource Overview

Geothermal assessment for Bulgaria indicates extensional_basin geological controls governing subsurface heat transport, yielding 20.6% of land area reaching the baseline target of 185°C at 5.5 km depth.

Uncertainty & Model Variance

Thermal inversion across Bulgaria shows consistent model convergence with constrained standard deviations across deep crustal layers.

Grid & Infrastructure Colocation

National electrical transmission coverage positions approximately 90.8% of prospective geothermal ground within 50 km of existing high-voltage corridors.

Geological & Basement Setting

Subsurface lithology is characterized by extensional basin dynamics with median sediment thickness of 2 km and crustal thickness of 35.1 km.

Stored Heat Volume

Accessible thermal energy in place between 3 km and 7 km depth above 80°C totals 45.3 Zettajoules (ZJ).

Peer Comparison

Benchmarked against 237 global assessment jurisdictions, Bulgaria demonstrates competitive positioning across heat flow, infrastructure, and basement competence indicators.

Target Sensitivity Analysis

Screening at 150°C baseline at 5.5 km increases prospective territory, demonstrating substantial deep EGS resource headroom.

Screening Methodology, Parameters & Limitations

This screening assessment for Bulgaria is generated from Geothermal Radar Data Pack 2026.1 utilizing global 0.1° hex-grid thermal inversion across 1 232 model cells (land area: 110 879 km²). Baseline prospective criterion is defined as reaching 185°C at or above 5.5 km depth with surface temperature normalized to 15°C.

  • Screening estimates represent regional-scale heat in place and do not replace localized 3D seismic or exploratory drilling.
  • Model uncertainties expand in regions with sparse deep boreholes and complex thrust fault kinematics.
  • Grid proximity indicators reflect line-of-sight distance to high-voltage transmission and do not account for local substation thermal capacity.
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