Baker TAML Level 6 design opened door to intelligent junctions
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By John Murphy, Houston
In 1998, Baker Oil Tools ran the world's first TAML level 6 multilateral well completion in a field trial in Bakersfield, California. TAML (Technology Advancement of MultiLaterals) is a semi-formal group of completion experts who have defined multilateral wells by how and to what extent the laterals and main bore are isolated from each other. They run from the simplest level 1, a simple open hole sidetrack, to higher levels with lateral casing liners and mechanical isolation to the highest level 6 which offers total hydraulic isolation and a cased lateral.
A level 6 multilateral junction that permits two branches to be drilled from the original wellbore is deformed at the surface and run through the standard main casing. Once in place, it is then swedged open to full size creating a steel fork in the wellbore. The result is a fully open, hydraulically sealed junction that accomplishes hydraulic isolation.
The Baker design field success is significant for several reasons. Though to date none have been commercially installed, the tests proved a method by which the completion, that is the junction and the lateral casing, could be placed into the well without milling the original main casing. That eliminated the steel millings left in the milled window that had made it nearly impossible to reliably achieve a good seal while maintaining a full opening at the junction.
The feat also created hydraulic isolation via casing, a definitive technological leap forward from the kind of isolation garnered by the cement sheath as in earlier versions. And while it has been reported current versions of the level 6 are not offering as much pressure integrity as had been hoped, that is equal to the main casing rating, it does offer considerably more than its predecessors.
But more importantly, the Baker level 6 design opened the door to the possibilities of intelligent junctions, the ability to affect operations at the junction remotely through wireless, electrical, or hydraulic conduit. And, say multilateral experts, once that technology is fully in place operators will make multilateral completions as common as horizontal wells.
"Now there is split between trying to do it wirelessly, which sometimes works and sometimes doesn't, or hydraulically, which works yet is clumsy," said one ML industry insider who, by virtue of having been involved in multilaterals since the late-1980s qualifies as a pioneer in a relatively young business. "That is really the cutting edge right now. It is limited to expensive wells and needs now to be expanded to the deep waters."
State-owned companies, Brazil's Petrobras and Norway's Statoil are considered leaders in the search for intelligent multilaterals. And, as with its predecessor, intelligent completions, the focus tends to be on flow control, essentially variable chokes. Halliburton is reported to have run one hydraulically controlled, indexing-type choke, meaning it can be set to specific openings and Schlumberger has run an infinitely adjustable, fully electric choke.
"They are going through a lot of designs right now," said one completions engineer. "Another feature companies are moving towards is measuring temperature and pressure in realtime with permanent downhole gauges. The ultimate goal is to be able to shut off the lateral with the shut off control about ten to 20 ft inside the lateral from the junction."
At the moment it is no trick close or regulate flow from the lateral. The challenge, and one which operators will certainly insist on overcoming, is to place the pressure, temperature, and flow control hardware in the lateral itself. Currently it must be placed in the main wellbore where operators fear it can become a flow restriction. To date, the technique has eluded the major multilateral companies including Baker, Schlumberger, Halliburton, and to a lesser degree, Weatherford.
"The main wellbore is cased first before the level 6 lateral liner can be installed," said one industry participant. "So the question is how do you then install the equipment and the hydraulic or electrical lines into the lateral. Just trying to do a level 5 or better is hard enough. No one has been able to figure it out yet but they are working on it."
The other service companies' Holy Grail is the ability to place level 6 completions from smaller main wellbores to accommodate the seven inch casings common in most deep and offshore wells, while leaving a reasonably large production liner in the lateral.
At present, Level 6 completions can be done only through 13 3/8-in casing with 9 5/8-in lateral liners, an unlikely production casing design in any but the shallowest wells. The Baker field test itself was done through a small main casing size but the lateral had to be cased with a 4 ½-in slotted liner – much too small to accommodate the kind of production necessary just to justify the expense of such an exotic completion.
One service contractor is rumored to be about to announce a successful 9 5/8-in version of the level 6 installation with two, 7-in laterals, but a company spokesperson has denied the design is close to field-test ready and reportedly relies on complex deforming and reforming operations.
Multilaterals enjoyed a great deal of industry interest in the mid-1990s but as one service company representative put it, "sort of fell from the radar screen in 1999." But in 2000 the market was rejuvenated when heavy oil producers in the Baja region of Venezuela installed more than 100 dual and triple laterals in high-angle wells. "Venezuela has done for multilaterals what the [Austin] Chalk [formation in Texas] did for horizontal drilling. They always knew they could drill [horizontal wells], in the Chalk if they learned how to complete them," said one TAML representative and advocate of multilateral drilling. "Now instead of explaining why you did a horizontal the boss wants to know why you didn't."
Comparing the multilateral well market future to that of the horizontal market's past is heard regularly from ML advocates. In the deepwater, where rig dayrates are exceeding US$250,000, they say, once the well is to depth more than one "straw" will be needed to drain the reservoir and multilaterals will be very cost effective.
For the moment, operators have replied that the high cost and lack of precedent make multilateral installations bad bets in these very expensive, high profile wells. And the cause was not helped when it was reported that Petrobras suffered the loss of a $40 million investment in late 2000 when a deepwater well was lost during an attempt to run a multilateral completion. And even ML suppliers admit current costs are prohibitive.
"It's a real interesting period right now," said one. "The industry has pretty well accepted the level 3, pretty well accepted level 4, no level 6 is imminent, and [the industry] is now moving on to the next thing which is controlling the individual laterals from the surface. We still have to get the price down, but that will come.
In the big picture, in these deepwater wells, the initial cost is not that much compared to what it gets you."
Once operators see it that way and as deepwater rig rates continue to climb, an explosion in the multilateral market does indeed seem likely.