Overview
Geothermal development is drilling-led and chemistry-blind. The oilfield has removed the drilling barrier — EGS, conversion of depleted hydrocarbon wells, dedicated geothermal rigs — but a second barrier remains: the chemistry of the water. Dissolved salts, silica and boron make produced hot water incompatible with district heating infrastructure, scaling pipes and heat exchangers and destroying reinjection-well injectivity.
ARBOK-GEYSER evaporates the whole stream at inlet temperature under deep vacuum, without membranes, filters, inhibitors, electrodes or consumables. It recovers near all of the water with no liquid tail, recuperates the large majority of the incoming heat, and retains every dissolved species as a dry, density-separable salt cake.
The economic consequence is the point. On a reference heating well the desalted-heat route yields approximately $960,000 per season against $40,000 of electricity cost, versus approximately $220,000 per year for the binary-cycle electricity route currently proposed for the same well — a four to fivefold difference before any mineral revenue. On metal-bearing brines the envelope rises to $5–10+ million per year.
Applications
District heating at typical network supply temperature; greenhouses at moderate warmth; drying and industrial process heat at lower temperature levels — outlet temperature is adjustable by design.
Oil and gas produced waters at 80–170 °C — already flowing in industrial volumes in the Permian and Marcellus basins and the Lower Indus trough, where the heat reaches surface and is discarded.
Critical-metal co-production from metal-bearing brines of Salton Sea type.
Geographic applicability: Hungary, Austria, Italy, Slovakia, Turkey, USA, Japan — the barrier is the same everywhere.
Underutilization illustrating the gap: Hungary has around 2,200 thermal springs and one of Europe's highest geothermal gradients, yet covers only 6–7 % of its heat market and around 11 % of district heating.
Operating Principle
Under deep vacuum the feed evaporates at a temperature equal to the inlet temperature — no heating, no boiling, no cooling. The vapour condenses as pure water; all dissolved species — salts, silica, boron and metals — remain as a dry cake or paste, subsequently separated by density into commercial mineral fractions.
Because the enthalpy of the vapour phase substantially exceeds that of the liquid, the process recuperates the large majority of the heat: purified water leaves at the temperature of the incoming stream. Adjusting the recuperation level gives direct control of outlet temperature — including raising it above the inlet value.
Reinjection strategy. Full withdrawal of formation water is hydrogeologically inadmissible — formation compaction and aquifer drawdown must be prevented. Water must be returned; the question is which water. Brine reinjection is precisely the failure mode of the incumbent approach. The appropriate candidate is the heating network's return flow — the same clean water after heat delivery. Injection volume is set by the reservoir's hydrogeological balance; salts remain at surface as separated mineral products; injectivity of clean water is stable, reducing pumping cost and extending field life.
Why membrane treatment fails on this feed — four compounding failures:
- Silica scaling. Silicic acid precipitates on membrane surfaces rapidly, limiting safe recovery and demanding heavy pretreatment.
- Boron passage. At neutral pH, RO rejects only about 50 % of boron; raising pH to 9–10 restores rejection but sharply increases chemical operating cost and corrosion.
- Thermal incompatibility. Polymeric RO membranes require feed cooling to approximately 25 °C — the treatment destroys the thermal product it is meant to enable, and the heat must be re-purchased downstream.
- Concentrate. Typical schemes reject 60–70 % of flow as brine with no legal surface discharge route. Reinjection energy is governed by wellhead pressure: at 10–30 bar specific energy is 0.4–1.1 kWh/m³; on wells with degraded injectivity, pressures reach approximately 80 bar and specific energy rises to approximately 3 kWh/m³. For one reference well that is 25–170 kW of continuous pumping — $35,000–120,000 per season in electricity alone, before chemicals and workovers.
Key Parameters
| Parameter | Value |
|—|—|
| Operating pressure | deep vacuum |
| Process temperature | equal to inlet temperature — no heating, boiling or cooling |
| Specific electric energy | very low, among the lowest reported for comparable produced-water handling |
| Water recovery | near-complete; no liquid tail |
| Heat recuperation | high-efficiency, substantially reducing net energy demand |
| Outlet temperature control | adjustable, including above inlet value |
| Outlet, district heating | matched to network supply requirements |
| Outlet, greenhouses | matched to greenhouse heating requirements |
| Outlet, drying and industry | matched to drying and industrial process-heat requirements |
| Residual solids | ordinary debris only (sand, calcites), usable in road base and construction |
| Consumables | none — no membranes, filters, inhibitors, electrodes |
| Form factor | containerized module, wellhead-mounted on asphalt or concrete |
| Reference capacity | scaled to a representative well's daily flow, illustrative — capacity scales by adding modules |
| Servicing | by standard oilfield crews |
Reference well and salt mass balance:
| Parameter | Value |
|—|—|
| Flow | 25 l/s (≈400 gpm, ≈13,600 bbl/day, ≈90 m³/h) |
| TDS | 3 g/l (3,000 ppm) |
| Heating season | 4,500 h |
| Salt transported per season | ≈1,200 t (≈6.5 t/day) |
| ΔT | 40 K |
| Thermal power | ≈4.18 MWt (≈14.3 MMBtu/h) |
| Seasonal heat | ≈18.8 GWht (≈64,000 MMBtu) |
| ARBOK electrical draw | modest, continuous — well within the range of comparable produced-water handling equipment |
| Coverage per well at peak | ~350–600 homes (peak household load 7–12 kW) |
Architecture and Components
Containerized module mounted at the wellhead on asphalt or concrete: deep-vacuum evaporation stage; vapour condensation to pure water; heat recuperation circuit returning water at inlet temperature with adjustable outlet control; dry cake collection with subsequent density separation into commercial mineral fractions; clean-water return path to the heating network and thence to reinjection.
Capacity is illustrated on a reference well's daily flow and scales by adding modules. Serviceable by standard oilfield crews — no specialist water-treatment personnel.
Advantages
Technical: no membranes, filters, inhibitors, electrodes or consumables; handles silica, boron and carbonates that defeat membrane systems; no cooling required, so thermal value is preserved rather than destroyed and re-purchased; outlet temperature controllable and can exceed inlet.
Water and waste: near-complete recovery with no liquid tail; zero waste discharge; residual solids limited to sand and calcites usable in construction.
Reinjection: clean return water gives stable injectivity, lower pumping cost and extended field life, instead of the brine reinjection that degrades the well.
Energy: specific energy consumption is very low — roughly one quarter of the specific energy required for high-pressure reverse injection of dirty concentrate.
Economic: minerals become a saleable stream rather than a disposal liability; on metal-bearing brines every dissolved metal is physically retained in the dry cake for selective recovery, with no raffinate stream to carry losses.
Commercial: leasing and BOOM structures require no capital investment from the well operator; produced waters shorten market entry because wells exist, water is already at surface, and infrastructure is amortized.
Integrations
ARBOK-Lithium · ARBOK-Rubidium · ARBOK-Cesium · ARBOK-VC (Vacuum Cracking) · ARBOK-CRYSTALLIZER · ARBOK LIGHT-SALT · ARBOK-Boron Separation (ASB)
Division of labour with the oil industry. The operator contributes drilling, stimulation, lifting and well inventory, and retains wells, heat offtake and energy revenue. ARBOK processes the stream and takes the mineral basket — bulk salts and, where present, lithium, rubidium, cesium and boron. Municipalities receive heat without fuel cost. The reservoir receives clean return water. The commercial interests divide without overlap.
Deployment & Operation
Wellhead-mounted containerized module, scaled to a representative well's flow, installed on asphalt or concrete and serviced by standard oilfield crews; capacity scales by adding modules. Return flow from the heating network is used as reinjection water, with injection volume set by the reservoir's hydrogeological balance.
Deployment models: leasing and build-own-operate-maintain (BOOM), requiring no capital investment from the operator. Produced-water sites offer the shortest market entry — wells and surface water already exist.
TRL
TRL 8. Reference-case techno-economics have been developed and published as a preprint (DOI 10.5281/zenodo.21380385), establishing the technical and economic basis validated for deployment planning.
Market Potential
The global geothermal market reached $6.99 billion in 2026. The first public offering of an EGS developer raised $1.9 billion. Four western US states formed a consortium targeting gigawatt-scale geothermal deployment, and US Department of Energy programmes support conversion of horizontal shale wells into geothermal systems. In 2026 major oilfield service companies announced dedicated geothermal-capable land rigs.
Regional scaling. A gigawatt of electric capacity by the binary-cycle route corresponds to roughly 2,500 wells of the 0.4 MWe class, with aggregate revenue of approximately $550 million per year. The same 2,500 wells through the desalted-heat route deliver about 10.5 GWt — peak heating for 0.9–1.5 million dwellings — worth approximately $2.5 billion per year, plus around 3 million tonnes of separated salts per season. The regional difference is on the order of $2 billion per year.
Mineral price bands: technical NaCl/KCl $35–115/t; CaCO₃ $25–70/t; precipitated silica $230–570/t; boric acid $800–1,400/t.
Typical Project Economics
One average well — heat route versus electricity route:
| Item | Value |
|—|—|
| Avoided fuel cost (gas boilers at 90 %, $46/MWh) | ≈$960,000 per season |
| ARBOK electricity cost (modest, continuous draw) | ≈$40,000 per season |
| Mineral revenue from 1,200 t separated salts | $50,000–200,000 |
| Total, desalted-heat route | ≈$1.0–1.1 million per season |
| Binary-cycle electricity route, same well | ≈$220,000 per year |
| Difference | 4–5× (+≈400 %) |
Binary-cycle reference: at resource temperatures of 120–150 °C net conversion efficiency is around 10 %, yielding about 0.4 MWe and 3.2 GWh per year; at a representative geothermal PPA of $70/MWh that is approximately $220,000 annually — before anti-scaling chemistry and full-flow reverse injection.
Metal-bearing brines — co-production scenario. For Salton Sea-type chemistry (Li 202 mg/l, Rb 110 mg/l, Cs 19.8 mg/l) the same hydraulics — 25 l/s, 405,000 m³ per season — transport approximately 82 t of lithium (≈435 t LCE), 45 t of rubidium and 8 t of cesium through the module per season. At 70 % recovery and the lower price band ($10,000–20,000/t Li₂CO₃, July 2026), lithium alone contributes $3–6 million per season — three to six times the entire heat effect. Cesium, at several thousand dollars per kilogram in a thin market requiring disciplined offtake, adds potential revenue in the tens of millions.
Monetization ladder of a single well: electricity ≈$0.22 million → desalted heat ≈$1.0–1.1 million → heat plus metals where present $5–10+ million per year, on the same water, wells and crews.
Risk Factors
Four assumptions bound the published analysis, stated by the authors:
- Binary-cycle net efficiency (~10 %) and PPA level ($70/MWh) are literature-typical, not project-specific.
- The 2,500-well regional model is illustrative — 1 GWe ÷ 0.4 MWe — not a stated consortium plan.
- Salt price bands are wholesale indications; merchantability depends on fraction purity and local logistics.
- The 70 % metal-recovery assumption for the selective stage requires pilot validation on each specific feed. Whole-stream retention in the dry cake is architectural, but finished-product yield is feed-dependent.
Additionally, heat revenue is seasonal at 4,500 hours while the electricity comparison is annualized — a conservatism in favour of the incumbent route.
Metal concentrations vary between wells by orders of magnitude and are excluded from the base case for that reason.
Related Technologies
ARBOK-Lithium · ARBOK-Rubidium · ARBOK-Cesium · ARBOK-VC (Vacuum Cracking) · ARBOK-CRYSTALLIZER · ARBOK LIGHT-SALT · ARBOK-Boron Separation (ASB) · TRISTONE (TEG-Electroliser)