An Enhanced Geothermal System Uses Oil And Gas Technology To Mine Low-Carbon Energy. Part 2.

Clara D. Flaherty


The US Division of Energy (DOE) has funded a challenge identified as FORGE in which incredibly hot granite rock will be drilled and fracked using the finest oil and fuel technological know-how. An all round aim is to see if drinking water pumped down a single well can be circulated by means of the granite and heated before pumped up a 2nd effectively to generate turbines that crank out electric power.

John McLennan, Department of Chemical Engineering, University of Utah, is the co-principal investigator for this DOE job. A webinar presentation on this subject was sponsored by NSI on April 6, 2022: Frontier Observatory for Study in Geothermal Power (FORGE): An Update and Lookahead

Aspect 1 tackled these concerns to John McLennan:

Q1. Can you offer a brief heritage of geothermal vitality?

Q2. What are improved geothermal systems, and where by is fracking used?

Q3. Inform us about the internet site of the FORGE task in Utah and why it was picked.

This writeup is Element 2, which addresses 3 further inquiries down below:

Q4. What is the primary structure of the injection and creation wells?

Six wells have been drilled to date. 5 of these wells are vertically drilled monitoring wells, which is regular with the technique of currently being a discipline laboratory. Fiber optic cables and geophones in the checking wells can map the chronologic progress of hydraulic fractures interconnecting an injection properly, which has been drilled, and an forthcoming generation well.

The injection nicely was drilled to a calculated depth of 10,987 ft (a real vertical depth of 8520 ft± beneath floor stage). This entailed drilling vertically and then setting up a curved portion at 5°/100 ft drilled, and last but not least retaining a lateral at 65° to the vertical, for about 4,300 toes in an azimuth just south of east (N105E). This course favors subsequent hydraulic fractures currently being orthogonal to the very well.

Just after drilling, all but the bottommost 200 ft of the nicely was cased (greater diameter 7-inch casing was utilized to transfer considerable quantities of drinking water with restricted friction and parasitic pumping losses) and cemented to the floor (to hydraulically isolate the annular space).

Q5. Could you summarize the three frac treatment options in the injection properly and their benefits?

In April 2022, three hydraulic fractures had been pumped around the decreased extremities (the toe) of the injection well. Geophones in 3 wells, surface instrumentation, and downhole fiber optic sensors deliver a look at of the evolving fracture geometries through pumping. Centered on the interpretation of these fracture geometries, the manufacturing properly will up coming be drilled to intersect these clouds of microseismicity.

A few fracture phases had been consecutively pumped. The initial focused the total openhole duration of the well (the decrease 200 toes that had not been cased). That remedy was slickwater (friction-lowered water). 4,261 bbl (~179,000 gal) were being pumped at premiums up to 50 bpm (2100 gpm). Soon after shutting in briefly, the very well was flowed back again at temperatures of about 220°F.

The future phase involved pumping slickwater at prices up to 35 bpm as a result of a 20-ft prolonged area of casing that experienced been perforated with 120 shaped rates to offer accessibility to the formation via the casing and the cement sheath. 2,777 bbl of slickwater were being pumped and then the nicely was flowed back.

The final phase entailed 3,016 bbl of crosslinked (viscosified) fluid pumped through perforated casing at premiums up to 35 bpm. Microproppant was pumped. In the foreseeable future, evaluations will be made to assess the requirement and viability of propping fractures to make certain conductivity of the developed fractures.

Preliminary processing of the third phase implies pseudo-radial fracture development, all around the perfectly at the centre. This favors a separation amongst the present injector and the upcoming producer on the purchase of 300 ft. A commercial scenario might demand increased offset than this however, this experimental application demands to 1st establish the capability to interconnect two adjacent wells with hydraulic fracturing.

Q6. What is the opportunity for commercial software?

In a business location, a multiplicity of hydraulic fractures would be developed to interconnect wells. At the FORGE field laboratory, the length of the lateral will be devoted to testing out new systems. These include things like approaches for deciding reservoir features, hydraulic fracturing and perforating techniques, conformance – nominally equal circulation by way of each and every hydraulic fracture, and the qualities of circulating by way of these fracture networks and the amount at which thermal depletion is expert. Analysis contracts are enable to other events (universities, countrywide laboratories, industrial entities) to create these technologies and take a look at them out at FORGE.

In a industrial EGS environment, chilly drinking water would be injected and pass via the array of hydraulically-created fractures, getting heat in the process. The hot h2o would be made to area by way of the generation effectively. At the surface area, standard geothermal technologies would be carried out for energy era (an organic Rankine cycle (ORC) plant, using a secondary organic and natural doing the job fluid that is flashed to vapor to drive a turbine/generator or, immediate flashing to steam). The generated water, just after warmth has been taken out, is recirculated.

The FORGE website will not be a energy producer. It is intended to be applied to take a look at and develop technologies that will endorse the commercialization of this kind of geothermal energy. Accomplishment facilities all over technological know-how improvement. Currently, sizeable innovations have been produced by advertising the application of polycrystalline diamond compact bits (PDC) that empower dramatic will increase in the rates of penetration. Analysis protocols of subsurface measurements and schooling of all rig internet site staff have enhanced the drilling economics of this geothermal project.

It appears that hydraulic fracturing can be properly carried out – but the legitimate test lies in circulation efficiency and warmth recovery after the generation well is drilled.

EGS achievement right here may perhaps be used somewhere else. Take into consideration employing hydraulic fracturing for hybrid EGS apps where by common purposes have encountered the geothermal equivalent of a dry gap – normal fractures have been not encountered throughout drilling but could be intersected by fracturing.

Achievement at FORGE means screening systems that would not in any other case be viewed as, passing feasible technologies to private business, and encouraging geothermal advancement overall.


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