A Taranaki shed­die invents a unique drilling aid for the oil and gas in­dus­try


The Shed - - Contents - By Ray Cleaver Pho­to­graphs: Rob Tucker

ATaranaki farm boy has come up with an in­ven­tion that could save the geo­ther­mal and oil and gas in­dus­try mil­lions of dol­lars — in his shed.

Well, Mark Hor­well is no longer a boy, though he was raised on a farm. In fact he has a de­gree in en­gi­neer­ing, his shed has some high-tech equip­ment, and the con­cept and de­vel­op­ment of his in­ven­tion have in­volved more than a dash of Kiwi in­ge­nu­ity. Mark has come up with a de­vice called a ‘Switch­float’, which en­ables drillers to work on prob­lems thou­sands of me­tres un­der­ground.

The Switch­float is ba­si­cally a non­re­turn valve that can be opened down­hole to al­low wire­line tools to be con­veyed down the well.


The Switch­float sys­tem pro­vides drilling op­er­a­tions with float-valve func­tion­al­ity while also al­low­ing the valves to be locked open when re­quired. All Switch­float valves are able to be locked open by either pump­ing a ball or us­ing a sim­ple wire­line tool. A clear path is cre­ated through the valve so that tools can be con­veyed safely within the drill string. Fol­low­ing this, the valves may then be closed to re­in­state float-valve func­tion­al­ity.

The ma­jor ben­e­fit of Switch­float is when the drill pipe be­comes stuck, it en­ables tools to be con­veyed down the drill pipe to find out where it is stuck, and cut the drill pipe off. Switch­float also al­lows sur­veys in the drill pipe with­out the re­moval of drill-string float valves.

“This re­duced trip­ping saves rig time, and wear and tear, and the de­vice al­lows

im­me­di­ate wire­line ac­cess in stuck pipe sce­nar­ios,” said Mark.

“It re­duces make and break cy­cles on drill-string-threaded con­nec­tions and there’s safety ben­e­fits as­so­ci­ated with re­duced drill-string move­ments.

“It also pro­vides the abil­ity to re­verse cir­cu­late through a drill string con­tain­ing float valves. The Switch­float sys­tem is a patented tech­nol­ogy and it has been suc­cess­fully uti­lized in geo­ther­mal air-drilling op­er­a­tions with well tem­per­a­tures ex­ceed­ing 300°C.”

The idea

Geo­ther­mal wells in New Zealand are of­ten drilled to around 3000m un­der­ground. High-pres­sure air and wa­ter are pumped down the drill pipe and re­turn up the an­nu­lus (out­side of the drill pipe) to lift the drilled rock out of the bore hole.

One-way non-re­turn valves are of­ten spaced about 150m apart down the string. This con­tains the pres­sure within the drill pipe and re­duces the time taken

The con­cept and de­vel­op­ment of his in­ven­tion has in­volved more than a dash of Kiwi in­ge­nu­ity

when adding ad­di­tional lengths of pipe to the drill string. How­ever, prior to the in­ven­tion of the Switch­float, if the drill pipe got stuck or any­thing went wrong, spe­cial­ist tools could not be low­ered through the valves to di­ag­nose or rec­tify the prob­lem.

Mark’s in­ven­tion changes all that. “To run a geo­ther­mal drilling op­er­a­tion can cost $100K a day,” Mark said.

“Pre­vi­ously, rec­ti­fy­ing a stuck drill string could be a hit-and-miss op­er­a­tion, sim­ply turn­ing the drill pipe back­wards and hop­ing it un­screws some­where good.

“This could mean long de­lays in the drilling pro­gramme, or pos­si­bly los­ing the en­tire well.”

Mark worked on geo­ther­mal rigs near Taupo putting di­ag­nos­tic and func­tional tools in the well and even set­ting off ex­plo­sive charges down the well to shoot holes into and cut the pipe if nec­es­sary.

“I thought there must be a bet­ter way to ac­cess the prob­lems and six years ago I came up with the Switch­float idea. I did the ba­sic de­signs and started the patent process to pro­tect the idea. I went to Con­tact En­ergy with the con­cept and they were pre­pared to run the pro­to­type.

“You can’t af­ford for these things to break down in a $20M well, so the valve bod­ies are man­u­fac­tured from 4145H high-ten­sile steel.”

The first Switch­float was as­sem­bled in Mark’s fa­ther’s trac­tor shed on the farm and the 250kg de­vice was shifted round with the farm trac­tor, a trusty Ford 3000. A big­ger shed was needed and Mark pur­chased a 6m ship­ping con­tainer and set it up on the farm, and a sec­ond con­tainer fol­lowed as Mark got more or­ders. The con­tain­ers were carted to the well sites then back to the farm.

“The Switch­floats are pretty heavy and I moved up from us­ing the farm trac­tor and chain blocks to buy­ing a fork­lift. That was a great in­vest­ment.”

Fully equipped work­shop

Two years ago Mark, his wife Lucy, and two boys aged three and one, bought a ru­ral prop­erty near Lep­per­ton in Taranaki and Mark con­verted the farm shed into a fully equipped work­shop.

“Hav­ing a good-size shed changed my life. It’s a bit iso­lat­ing some­times work­ing for my­self, but the boys like to watch the ac­tion and check things out,” he told us.

Mark out­sources most man­u­fac­tur­ing of parts to sup­pli­ers in New Zealand and the US, and he as­sem­bles the fi­nal prod­uct him­self.

He makes some of spe­cial­ized parts of the tools him­self and for this he pur­chased an elec­tri­cal discharge ma­chine (EDM), which is a wire cut­ter de­signed to ac­cu­rately cut very hard ma­te­rial with high-cur­rent pulses of elec­tric­ity. They are mainly used for tool and die mak­ing, etc.

“It’s quite a tool. It’s like a real fancy band­saw. It cuts with a .25mm brass wire and the cool­ing wa­ter is de-ionised so it won’t con­duct elec­tric­ity,” said Mark. The ma­chine was pre-dig­i­tal and an in­ter­face board was added to al­low the ma­chine to be com­puter con­trolled.

Mark has just pur­chased a milling ma­chine and is get­ting a metal lathe and told us that he is at present work­ing on an­other new tool de­sign for the oil and gas in­dus­try.

“I re­ally need a big­ger shed al­ready,” he said.

Check out his web­site switch­float.com.

The first Switch­float was as­sem­bled in Mark’s fa­ther’s trac­tor shed on the farm

Right: The patented valveopen­ing de­vice in the Switch­float Be­low: The non-re­turn valve on the Switch­float

Above: Mark Hor­well and his Taranaki work­shop Far left: The con­trol panel for the EDMLeft: The EDM cuts high­t­en­sile steel with elec­tri­cal pulsesBe­low: Mark’s ru­ral shed, where it all hap­pens

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