We investigate the ground with geophysics calibrated on geotechnical boreholes, build the lithological profile along the route and design the bore on it: geometry, pullback force, pipe stresses, buoyancy and drilling-fluid pressure. We work on natural gas and crude oil transmission pipelines in Romania, Bulgaria and North Macedonia.
Project register Request a proposalThe bore profile is drawn on the interpreted geological section, with the host stratum chosen from the investigation. Each check rests on a guideline or standard of European HDD practice, in the edition in force at the date of the design.
Schematic, vertical scale exaggerated. α and β are the entry and exit angles, R the bend radius, h the cover to the pipe measured from the design scour level and L the drilled length. U1, U2 and U3 are the lithological units of the interpretive profile; the bore stays in U2.
Entry and exit angles, minimum bend radius, cover below the design scour level and an alignment kept in the chosen stratum. At the Vardar River the 900 m radius meets R ≥ 1 200 · OD for the Ø711 mm pipe.
DCA Technical Guidelines, 5th ed. (2025)Segmented model, computed element by element from the pulling head to the tail of the string, with wall friction, the capstan effect in the bends and fluid drag.
ASTM F1962-22, adapted to steel · PRCI · ASCE MOP 108, 3rd ed. (2024)Tension, bending in the curves and external pressure, checked in combination, and the collapse resistance of the wall.
NEN 3650-2:2020+A1:2024 · API 5C3 / ISO 10400Apparent weight of the pipe in the drilling fluid and the ballast that keeps pullback force and friction within the rig's capacity.
ASCE MOP 108 · DCA Technical GuidelinesAllowable ground pressure along the bore compared with the pressure needed for circulation, so that the fluid neither fractures the ground nor breaks out at the surface or into the river.
NEN 3651:2020 · Luger & Hergarden, Delft Geotechnics (1988)Wall thickness, steel grade and design pressure, to the code of the country where the line is built.
EN 1594:2024 · API 5L · SR EN ISO 3183 · ANRE Order 118/2013 · CONPET standardsGeophysics covers the route continuously between boreholes, and the boreholes calibrate it. Together they give the interpretive lithological profile on which the bore is designed.
| Method | What it gives | Where we used it |
|---|---|---|
| High-resolution 2D seismic reflection | geometry of the layers and contacts beneath the river bed | Vardar River; Poarta Albă – Midia Năvodari canal |
| Seismic refraction | P-wave velocities and depth to stiff layers | Vardar River |
| MASW and MAM | shear-wave velocity (Vs) profile with depth | Vardar River; Kozloduy, to a 225 m target depth |
| Downhole seismic | wave velocities measured in the borehole, with a 500 kg gravity source | Kozloduy, Units 7 and 8 |
| Geoelectrical survey: resistivity tomography, vertical electrical sounding | lithological contrasts and saturated zones | Vardar River; Vertical Corridor, Rupcha – Vetrino |
| Geotechnical boreholes, dynamic probing | stratification, grain size and design geotechnical parameters | Rupcha – Vetrino; Vardar River |
| Hydrological study | discharges and scour depth | Poarta Albă – Midia Năvodari canal |
| Thermal resistivity | heat dissipation around a cable installed by HDD | Copșa Mică solar plant connection |
A selection of works documented by contract or by the design documents, in reverse order of the contract year. The right-hand column states what the company did on each.
| No. | Obstacle crossed | Pipeline or line | Country | Year | Company scope |
|---|---|---|---|---|---|
| 1 | DN150 Iancu Jianu – Balș gas pipeline | 110 kV underground power cable | RO | 2026 | design |
| 2 | Vardar River | gas, DN700 Gevgelija – Negotino, Ø711 × 14.2 mm | MK | 2026 | HDD design and verification report; geophysical and geotechnical study |
| 3 | Olt River, at Ostroveni | gas, branch line to DN400 Govora – Drăgășani | RO | 2026 | geotechnical and geophysical studies; design; supervision |
| 4 | Poarta Albă – Midia Năvodari canal | crude oil, 14 and 28 in Constanța – Bărăganu | RO | 2025 | hydrological and geotechnical studies; geophysics including seismic reflection |
| 5 | Golyama Kamchiya River, km 22+909 | gas, DN1200 Rupcha – Vetrino, Ø1219 × 17.5 mm | BG | 2025 | geotechnical boreholes; geophysical and geotechnical study; HDD design; construction support |
| 6 | Glavnitsa River, km 37+149 | gas, DN1200 Rupcha – Vetrino, Ø1219 × 17.5 mm | BG | 2025 | geotechnical boreholes; geophysical and geotechnical study; HDD design; construction support |
| 7 | Provadiyska River, km 51+453 | gas, DN1200 Rupcha – Vetrino, Ø1219 × 17.5 mm | BG | 2025 | geotechnical boreholes; geophysical and geotechnical study; HDD design; construction support |
| 8 | Route of the Copșa Mică solar plant cable connection | underground power cable | RO | 2025 | geotechnical, geological and geophysical study; interpretive lithological profile for HDD |
| 9 | Struma River, km 1+500 | gas, DN700 Kulata – Kresna, Ø711 × 14.2 mm | BG | 2025 | geotechnical and geophysical study; HDD design, built as designed; construction support |
| 10 | Struma River, km 4+500 | gas, DN700 Kulata – Kresna | BG | 2025 | geotechnical and geophysical study; HDD design, built as designed; construction support |
| 11 | Struma River, km 7+300 | gas, DN700 Kulata – Kresna | BG | 2025 | geotechnical and geophysical study; HDD design, built as designed; construction support |
| 12 | Strumeshnitsa River, km 13+100 | gas, DN700 Kulata – Kresna | BG | 2025 | geotechnical and geophysical study; HDD design, built as designed; construction support |
| 13 | Struma River, km 45+500 | gas, DN700 Kulata – Kresna | BG | 2025 | geotechnical and geophysical study; HDD design, built as designed; construction support |
| 14 | Salina Turda, network of 12 drains | drains for infiltration water | RO | 2022 | geotechnical and geophysical study; design |
| 15 | Danube River, at Cernavodă (C1–C2) | crude oil, Ø20 in and Ø28 in Constanța – Bărăganu | RO | 2021 | geotechnical and geophysical studies; design; permitting; construction support |
| 16 | Borcea branch, at Fetești (C3–C4) | crude oil, Ø20 in and Ø28 in Constanța – Bărăganu | RO | 2021 | geotechnical and geophysical studies; design; permitting; construction support |
RO Romania · BG Bulgaria · MK North Macedonia. Items 5–7 and 9–13 belong to the Vertical Gas Corridor (Bulgartransgaz EAD), item 2 to the Greece – North Macedonia interconnector.
For the larger projects we link to the press that covered them: news agencies, trade journals and the press releases of the transmission operators and of the banks financing them.
The articles describe the infrastructure projects our work is part of. The company's contribution is the one stated on each project card; the articles do not cover it.
Five HDD crossings of the Struma and Strumeshnitsa rivers on the pipeline that raises transmission capacity between Greece and Bulgaria. We carried out the geotechnical and geophysical studies, designed the bores and supported construction. The crossings were built as designed.
Three river crossings on the pipeline that doubles Bulgaria's exit capacity to Romania at the Negru Vodă / Kardam point. The work started with the geotechnical boreholes, continued with the geophysical and geotechnical study and covers HDD design and construction support.
HDD design for the Gevgelija – Negotino section and the final design verification report issued before drilling, built on the geophysical and geotechnical study of the route: high-resolution 2D seismic reflection, refraction and MASW, geoelectrical survey, dynamic probing, geotechnical boreholes and an interpretive lithological profile.
Geological and geophysical study for the site of the two AP1000 units: MASW and MAM seismic surveys on four lines to a minimum target depth of 225 m, seismic source generation for downhole tests and integrated interpretation with the geotechnical boreholes.
HDD replacement of the crossing lines of the Constanța – Bărăganu pipelines, in place of the 12¾ in lines laid in 1968–1978. We carried out the geotechnical and geophysical studies, the design, the permitting and the construction support; the six bores were drilled in three months. The work was presented with Horizontal Drilling International at the DCA Europe annual congress.
Geotechnical and geophysical study and design of a network of 12 drains installed by HDD, for long-term drainage of the western overburden hill.
Hydrological and geotechnical studies and geophysics, including seismic reflection, for the HDD replacement of the Constanța – Bărăganu lines at the canal crossing.
In 2026 we are also designing the diversion of the Ø20 in Bărăganu – Onești crude oil line at the Focșani – Brăila expressway and the replacement of about 3 km of the Ø10¾ in crude oil line at Independența, both for CONPET S.A., and the protection of the DN150 and DN600 gas pipelines at the 110 kV underground cable in Balș.
Photographs from sites where we worked alongside the contractor, from stringing the pipe to pulling it through the bore.
Atanasiu & Skills S.R.L., formerly Atanasiu Proiect S.R.L., has worked from Târgoviște since 2019. Design, survey, geophysics and geotechnics sit in one team, so the bore profile is drawn on data acquired and interpreted by the people who design it.
The company is led by Eng. Dragoș Alexandru Atanasiu, an engineer in Mining, Petroleum and Gas, specialised in Hydrocarbon Transmission, Storage and Distribution (Lucian Blaga University of Sibiu, top of the graduating class), and an ANRE-licensed PGT designer for natural gas transmission systems. Eng. Atanasiu designed the crossings on the Kulata – Kresna looping and the Vardar River crossing, led Lot 3 of the Vertical Corridor as chief project engineer and was project manager of the geological and geophysical study for Kozloduy Units 7 and 8.
CONPET S.A. rated the company "very good" for design and field studies in recommendation no. 34670 of 02.11.2020. We have been an associate member of DCA Europe since 2023, at the invitation of the association's vice-president.
