V V~_A_/PIPELINEs®

Volume 11 Number 05- May 2011

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Jim Tolly, Farwest Corrosion Control Company, USA,explains how directional drilling can be performedsafely and efffectively, even in difficult conditions.

I n the pipeline industry, a common method used to install a section of new

pipe is via a directional drill. This is done when it is either impractical orimpossible to dig an open trench, such as under a highway, body of water,railroad, environmentally sensitive area, or in a heavily congested residential or

commercial area. Directional drilling technology has improved to the point that thismethod of pipeline installation is now regularly, safely, and effectively undertakenworldwide.

The basic process consists of drilling a pilot hole, reaming it a number of timesto the appropriate size, attaching the new pipeline to the end of the drill pipe,and pulling the new section of pipe back through the bore. However, in the sameway that all construction projects encounter unexpected surprises, directionaldrilling projects seem to encounter more than their fair share. For example, adrilling contractor may have an excellent idea of what to expect once drilling hascommenced based on previous projects in the area and geological surveys. Thereality is that drilling into an unforeseen hard rock formation can lead to moreexpense, work, and frustration, and require significantly more time to complete theproject.

How do you take this already difficult process, which is fraught with challenges,and make it even more challenging? One way would be to ream the bore to a

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CONQUERINGCHALLENGES

c~Figure 1. Pipelines pulled through the bore of a directional drillare subjected to stresses that can very easily damage or destroytheir protective coatings.

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diameter of 54 in., and instead of pulling one new pipesection through it, you pull 10 bundled casings, totallingnearly 2100 ft in length. This was the task facing a projectowner, group of engineers, pipeline and drilling contractorand crews, and sales and technical representatives.

In September 2009, an engineering firm in charge ofthe design for this directional drilling project contacted JimTolly of the Corrosion Control Products Company divisionof Farwest Corrosion Control Company, for assistance.Their project consisted of 10 bundled casings, including3-l4in.,2-l2in.,2-lOin.,1 -6in.,and2-4in.pipecasings, which were to be installed under a network of newrailroad tracks in an area being dramatically redevelopedto transport freight. The engineering firm was interested infield-applied coating options for the girth welds on each ofthe casings.

When deciding on which field-applied girth weld coatingto approve for use, the engineering firm had to ensure thatthe coating: (a) had to be designed for use in a directionaldrilling application; (b) had to be compatible with the plantapplied coating; (c) had to offer the same corrosion andmechanical protection as the plant-applied coating; and (d)had to have a proven track record of successful use.

Pipelines pulled through the bore of a directional drill aresubjected to stresses that can very easily damage or destroytheir protective coatings. Rock, shale, and gravel can cutthrough or abrade coatings all the way to the pipe surface.Consequently, coatings used in directional drilling projects aretypically sturdier and more abrasion resistant than those usedin direct bury applications. Additionally, girth weld coatingsare sometimes viewed as being the weak link in the pipelinecoating chain, adding to the importance of choosing the rightproduct for the job.

There are a multitude of field-applied girth weld coatingsavailable for use in directional drilling projects: field-applieddual layer fusion bonded epoxy, liquid epoxies, cold-appliedtapes covered with a fibreglass protective outer wrap, and2-layer and 3-layer heat shrink sleeve systems, etc. There arenumerous coating options that will complement plant appliedcoating systems and also provide effective corrosion andmechanical protection.

When the goal is a successful field-applied coating system,a number of equally important components are required:

Coating choice. Choosing the right product for eachproject is critically important. The decision is usuallymade based on the pipeline operating temperature,compatibility with the plant applied coating, and themethod of pipeline installation.Contractor and inspector training. Regardless ofprevious experience, at the start of each project, thepipeline contractor’s coating installation crew and thecoating inspector should be trained to apply the coatingbased on the manufacturer’s requirements.Proper pipe surface preparation. To what degree doesthe pipe need to be cleaned? This will be specified bythe coating manufacturer, and its primary purpose is topromote maximum coating life.

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Figure 2. Coatings used in directional drilling projects are typicallysturdier and more abrasion resistant than those used in directbury applications.

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Figure 3. Rock, shale, and gravel can cut through or abradecoatings all the way to the pipe surface.

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Figure 6. There are numerous coating options that willcomplement plant-applied coating systems and also provideeffective corrosion and mechanical protection.

Coating application or installation. Coatings must beinstalled according to the manufacturer’s guidelines.Coating inspection, both visual and with a holidaydetector; and when necessary, coating repair.The plant-applied coating on the casings was a

three-layer polypropylene system. Tolly worked with theengineering firm to specify Canusa-CPS TBK-PP-65heat shrinkable three-layer directional drilling kitsfor the girth welds, which were previously used ondirectional drills in the project area and have a longhistory of successful use. Each kit comprises: (a) a100% solids, liquid epoxy primer, which becomes theprimary anti-corrosion layer; (b) a heat shrink sleevewith a polypropylene backing and a high shear, hot-meltadhesive. This heat shrink sleeve also provides corrosionprotection to the girth weld and mechanical protectionagainst the stresses encountered when the new pipeis pulled through the bore; and (c) a secondary heatshrinkable sleeve is included in each kit and functions asa sacrificial wear cone.

In January 2010, the pipeline contractor started workon the project and by early February was ready to begincoating the girth welds. Farwest’s Corrosion ControlProducts Company division supplied the contractorwith Canusa-CPS TBK kits. Along with Scott Smith andSteve Anderson from Canusa-CPS, Tolly provided onsitepipeline contractor and inspector training.

In order for the end result to be a high qualityproduct, the pipeline contractor’s installation personneland the pipeline owner’s quality control representativeswere trained per the manufacturer’s recommendations.Training included proper pipe surface preparation andthe directional drill kit installation, inspection, andrepair.

The installation procedure for Canusa-CPSTBK-PP-65 heat shrinkable three-layer directional drillingkits consisted of:

Ensuring the girth weld area was clean by wipingdown the adjacent plant-applied coating and the baresteel with a solvent-soaked rag in order to removegrease, oils, and other surface contamination.Abrasive blast cleaning the bare steel girth weld to aminimum of a NACE 2/SSPC-SP1 0 near white metalfinish, with 2 - 4 mils of anchor profile. The adjacentplant applied coating was lightly abraded with60 grit sandpaper. The plant applied coating edgeshad already been chamfered to less than 30 by thecoating plant.The bare steel girth weld was preheated with ashrink sleeve torch in order to raise the temperatureto 105 - 120 F This was done in order to dry anymoisture in the steel and to allow the liquid epoxyprimer to better flow into the anchor profile.The 100% solids, liquid epoxy primer was thoroughlymixed and then painted on the bare steel to anaverage thickness of 6 mm.

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Figure 4. There are a multitude of field-applied girth weld coatingsavailable for use in directional drilling projects.

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Figure 5. Pulling bundled casings.

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The liquid epoxy primer was force cured with the shrinksleeve torch, and the girth weld and the adjacent plantapplied polypropylene coating temperatures were raisedto 195 F Silicone heat bands were placed over theadjacent plant-applied coating in order to keep the torchflame from damaging the polypropylene.The primary heat shrink sleevewas centred over the girthweld, loosely wrapped aroundthe pipe, and shrunk downfrom the centre to each edgewith the shrink sleeve torch.Once the shrinking of theprimary sleeve was completed,and while its polypropylenebacking was still hot and soft,a hand roller was used toremove any entrapped air.The sacrificial shrink sleevewas centred on the leadingedge of the primary heatshrink sleeve, looselywrapped around the pipe,and also shrunk with thetorch. Hand rolling followed.Once the primary heat shrinksleeve and the sacrificialshrink sleeve had cooleddown to 120 F, additionalliquid epoxy was paintedaround the leading edge ofthe sacrificial sleeve.

After installation, theTBK-PP-65 kits were visuallyinspected for coating damageand then high voltage holidaytested.

Eventually, all of the girthwelds on each of the casingshad been coated. The separatecasings were then bundledtogether on top of custom-madepipe rollers. On one end of thecasing bundle, a pulling headwas fabricated. Its purpose wasto allow the casing bundle to beattached to the end of the drillpipe where it exited the bore.

Finally, the drilling of the pilothole was completed and the borewas reamed a number of timesto the appropriate size. The endof the drill string was attachedto the pulling head on the endof the casing bundle and pipepullback began. After only a fewhours, the entire casing bundlewas pulled into the bore.

The good news: challenges led to solutions thatbrought successful results. The casings are in place andwill allow the enclosed pipelines to transport oil, water,gas, electrical and instrumentation cables from theirsources to their destinations.

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DRIVING INNOVATIONTRANSFORMING CONSTRUCTION

Michels Corporation is one of the leading utility contractors in North Americaand ranked as the 45th largest contractor on ENR’s lop 400 Contractors. Ourteam of 5,000 employees and 9,000 pieces of equipment provides engineeringand construction services in the energy, transportation, communications andutility industries.

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