A look at Well Designs in a Mature Basin
The following material is based on Chinook’s experience in the Western Canadian Sedimentary Basin, not on all wells drilled in Canada. While the image may be incomplete, Chinook’s exposure to well drilling in the basin is large enough to be a representative sample of general trends in the area.
Drilling wells in a mature basin evolves in a very dynamic fashion. Twenty years ago, most wells drilled in Canada were vertical. The pursuit of resource plays lead to a wide adoption of horizontal drilling in the maturing Western Canadian Sedimentary Basin. Horizontal wells became more common in the early 2000’s, and became prevalent by 2010. A large proportion of wells currently drilled in the basin are horizontal, drilled either for unconventional shale (developed with multi-stage fracking) or for thermal oil sands (stimulated with steam).
A smaller number of wells are drilled in conventional cold-flow oil reservoirs. It is in this space that well geometry has evolved dramatically over the last decade.
Back in the early 2000s, natural gas was driving the oil patch in Canada. Development included a large number of shallow gas wells, coal bed methane (CBM) developments and deeper carbonate gas wells. The Jean-Marie play in North-Eastern British Columbia was Encana‘s crown jewel at the time, and many technological advances were shaped in that play, starting with underbalanced drilling (paralleled by the evolution of managed pressure drilling systems) and ending with the use of natural gas produced while drilling to power drilling for said gas. In the late 2000s, Jean-Marie wells were drilled as 2 and 3-leg multilaterals (with one bit drilling all lateral sections and multiple MWD batteries packed in the drill string to avoid trips).
Lateral lengths ranged from 1,000 to 1,500 meters. The Jean-Marie is a relatively high permeability gas reservoir. Low drainage radius was not the reason for this design, but rather efficiency and lowering drilling costs drove the technology forward.
Dual legs were drilled in the Viking Formation at Redwater by Sure Energy as early as 2010 and Mancal was drilling 4-leg Viking wells by 2011 in the area North-East of Edmonton.
Many dual leg horizontal wells were drilled in the Bakken trend in South-East Saskatchewan by Petrobakken (now Ridgeback Resources) and Crescent Point, from 2009 onward.
Multilateral wells were widely used to blanket the Bluesky Formation in the Peace River oil sands. Open hole completions, low API oil and the drive to lower costs made this design one of the more effective ways to develop the play. Baytex, Murphy Oil and PennWest have used multilateral open hole wells to develop the heavy oil with cold flow methods since 2013 in the Seal and Walrus fields.
Multilateral wells emerged as an efficient way to develop Clearwater wells in the Marten Hills trend. Companies (including Spur Petroleum, Deltastream and to some degree Cenovus Energy) utilized the concept from 2016 onwards.
The lower Clearwater sand is 10-20 meters thick in this area, but the reservoir is relatively dirty (with low permeability due to clay content) and charged with low API oil. In order to increase recovery in the low-drainage-radius sand, wells are drilled at tight spacing. Four to eight legs are drilled from every build section in order to keep drilling cost down. Further lowering cost is the barefoot completion: no production casing is run, as the formation is competent enough to produce oil without collapsing. It would also be difficult and cost prohibitive to run liners in all the separate legs.
Similar multilateral wells are now routinely drilled in Mannville targets (Sparky, Cummings, Dina, McLaren, General Petroleum, Rex, Lloydminster) in East-Central Alberta, throughout fields from Provost to Lindbergh.
Multilateral wells were drilled by CNRL and Gear (developing Cummings Sand in Lindbergh); CNRL and Husky (developing Sparky in Wildmere) and West Lake (developing their Rex play in Swimming) with multilateral wells, with 4 to 8 legs each, since 2017.
Feather and fishbone designs
A precursor to fishbone and feather wells were collector multilaterals drilled between existing pads of Bluesky wells in the Peace River oil sands. A few wells drilled by PennWest in Walrus and Peace have 10 to 20 legs, and are drilled in a hybrid feather design, with a few long straight legs (acting as collectors) and a large number of short curved legs (extending to every un-drained area between previously drilled pads). One such well, 100/15-01-083-18W5/0, drilled in 2016, has 47 legs, for a total lateral length of over 25,000 meters.
Devon experimented and successfully implemented fishbone designs in their Wolf Lake property, to augment recovery in a play developed largely with slant wells (up to that point). The first fishbone multilateral was drilled in 2017 at 100/14-19-063-06W4/0. It would lead to the development of stacked fishbone multilaterals a year later.
Baytex replicated the design in their 100/08-33-062-09W4/0 well, drilled in 2018, side by side with a multilateral well.
CNRL and Gear are drilling Sparky feather design wells (short reach radial wells sidetracked from a main well) in Wildmere since 2018.
Another variant of the fishbone design was executed successfully by PetroChina Canada (Brion Energy at the time) in their McMurray SAGD property in MacKay, in 2019. Individual legs of producer wells were drilled upwards, to penetrate more layers of the McMurray formation.
Stacked wells are typically drilled one on top of another in thick formations such as the Montney in British Columbia and Alberta Deep Basin region, or in the Wolfcamp/Spraberry trend in the Permian Basin. These are unconventional wells stimulated with multi-stage fracking, where well geometry is optimized for fracking efficiency. That technological evolution is spectacular, but a subject for another post.
On the conventional spectrum, stacked multilateral wells offer potential for increased recovery and ROI, provided, among others factors, that the sandstone reservoirs are thick enough. The approach addresses challenges related to low permeability and viscous oil.
Spur Petroleum, and then Deltastream, deployed stacked multilaterals in Marten Hills. As mentioned before, the reservoir exhibits low permeability and the hydrocarbon contained within is heavy oil. Drainage radius is reduced, and in places at Marten Hills, reservoir thickness is significant, reaching upwards of 20 meters.
One approach, applied mostly by Deltastream, was to alternate placement of the legs of a multilateral well, one deeper, one shallower, creating a wine-rack geometry.
Another approach, applied often by Spur, was drilling sets of multilaterals on top of each other. In one instance (107/14-32-073-24W4/00), Spur drilled a third layer of laterals below two existing layers, resulting in a triple stack of holes, all placed within the Clearwater sand (the lower multilateral well is used for disposal/injection).
CNRL drilled stacked Sparky and General Petroleum multilateral wells in Wildmere, with each set of legs targeting separate channels (different formations).
Devon demonstrated the stacked well concept in their Wolf Lake property, where they stacked 3 layers of fishbone wells, one set placed in the Sparky and two sets in the General Petroleum Formation. One of the first stacked multilaterals was well 102/13-28-063-06W4/09, drilled in August of 2018. A series of similar wells were drilled in the region until 2019, when the asset was sold to CNRL.
Drilling stacked fishbone wells is largely an exercise in geosteering and data management, with learnings from one leg applied to the next.
Geosteering wells with complex directional designs
Chinook assists operators with services related to geological wellsite supervision and specialized geosteering deployed in the field and remotely. Chinook geologists have supervised over 10,000 wells in the Western Canadian Sedimentary Basin, with over 1,500 supervised using software driven geosteering methods.
In recent years we have developed workflows tailored to multilateral wells and complicated well designs, by leveraging software capabilities and in-depth knowledge of the target reservoirs.
Data analytics are deployed at well level and also at pool and field level, allowing for objective quantification and quantitative evaluation of parameters.
©2020, Chinook Consulting Services