best practices emerging for erd wells

8/11/2019 Best Practices Emerging for Erd Wells

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Once again, experience proves to bethe best teacher as operators find suc-cess at the end of a long string.

By DICK GHISELIN, Senior Editor

Progress in extended reach

drilling (ERD) continues toamaze. The industry has broken

the 40,000-ft (12,200-m) barrier and ishungry for more.

Recently, BP announced a contractwith Parker Drilling Co. to build a newland drilling rig on BPs Endicott fielddrilling pads on Alaskas North Slope.The rig design will incorporateParkers extensive ERD experience but

will be owned by BP. Drilling isexpected to begin in 2010. The target BPs Liberty offshore discovery in

Foggy Island Bay lies about 20 miles(32 km) east of the Prudhoe Bay com-plex. According to the company,Liberty development will require ERD

wells stretching as far as 8.3 miles (13.3km) from the surface location to tap areservoir around 11,000 ft (3,354 m)deep. This ambitious goal tops the cur-rent North Slope record for ERD by24,175 ft (7,370 m).

The confidence to attempt such adrilling feat comes from two sources:personnel competency and drilling

technology. Parker combines a strongreputation for designing and manufac-turing purpose-built extreme-capabil-ity drilling units with arctic ERD wellconstruction experience on RussiasSakhalin Island, where a land-basedrig drills ERD wells under the Sea ofOkhotsk.

Successful ERDTheres more to drilling a successfulERD well than building a giant rig.The current world record ERD well

was drilled under the Persian Gulf by

Transoceans GSF 127 jackup, a fairlystandard drilling unit.

Delving into the best practices cup-board for ERD, one finds several itemsthat have nothing to do with the rig.Prior planning and geomechanical

modeling of the rock to be drilled areevery bit as important to success as thechoice of rig and equipment.Drillstring and bottomhole assembly(BHA) designs must be a perfectmatch with the intended wellbore tra-

jectory to minimize torque and drag.Drilling fluid design must be optimumto control the well while providingmaximum lubricity and cuttings trans-port qualities, as well as minimizingformation damage. Logging-while-drilling (LWD) data must provide

high-quality relevant information to

support steering decisions. Andtelemetry and control systems must beable to maintain reliable communica-tion with the BHA to deliver timelydrilling parameters and formationevaluation data to surface as well as

the downlinking capability to executesteering decisions.Intense attention to detail starts

from the beginning. Experience hasshown that taking care to drill a gun-barrel straight vertical section pays offhandsomely when building the curveand lateral sections. Using rotary steer-able systems eliminates slide drillingand optimizes penetration rates whileensuring that the drill string is alwaysturning while drilling. Augmentingrotary speed by including a mud motor

in the BHA allows higher bit rotational

Multilateral /Extended Reach

Best practices emerging for ERD wells

www.EPmag.com September 2009 | E&P

Figure 1. The worldwide ERD database will take on a new profile if BP is successfulstepping out 8.3 miles (13.3 km) on its Liberty field development project.

As seen in theSeptember

2009 issue of


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speeds without overtaxing the topdrive and facilitates penetration rate,especially in the far reaches whereweight-on-bit is limited.

Precise geosteering in ERD wells isnot a luxury. It is a necessity. Even onemisstep that causes the drillers to pullback and sidetrack can prevent an ERD

well from reaching its planned totaldepth (TD). For this reason, LWDstrings must be designed to include

measurements that allow directionaldrillers to identify bed boundaries,faults, fluid contacts, and other drillinghazards in time to steer away fromthem. Fortunately, several excellentboundary mapping tools exist that canhelp guide the directional drillers.

If successful, the BP ERD wells atLiberty field will take their placeamong other record-setters, starting

with the BP Wytch Farm development,Totals Austral field wells in Argentina,and ExxonMobils wells at Sakhalin

Island (Figure 1). These wells weresimilar in that they were all drilledfrom land drillsites. The current recordbelongs to Maersk Oil Qatar in the AlShaheen field and is the only onedrilled from an offshore rig.

Interestingly, according to a Maerskspokesman, the company was not try-ing to set a record. It had planned todrill through the Kharaib B andShuaiba carbonates and the extremely

thin Nahr Umr sandstone and, oncethat goal was achieved, continue todrill to maximize reservoir contact. Inso doing, it made history.

The Maersk well provides a perfectexample where the application of bestpractices pays off. Had the company notemployed best practices for ERD drillingfrom the outset, it is highly unlikely arecord would have been set. Advanceplanning and attention to detail duringthe course of well construction set thestage for a record performance.

The job is not doneuntil the oil flowsDrilling a record-setting ERD well isone thing. Casing and completing it isanother. Best practices combined withinnovative equipment and experiencedpersonnel are also essential ingredientsfor a successful completion.

An example comes from SakhalinEnergy, a consortium of Gazprom,Shell, Mitsui, and Diamond Gas

Division of Mitsubishi, where attentionto small details paid off while casingseveral 3-D directional wells in thePiltun-Astokhskoye project onSakhalin Island.

Hitting casing points accurately is amajor factor in successful directional

well construction. A key enabler is theability to rotate casing to bottom and

while cementing to achieve uniformcement distribution around the casingand ensure hydraulic isolation.

While running a 7-in. liner to 12,464

E&P | September 2009 www.EPmag.com


Figure 2. Rotational torque calculations in both oil-based mud (blue) and cement slurry (green) compare favorably with actualmeasured torque on bottom when special low-friction centralizers are used.


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ft (3,800 m), torque and drag loomedas potential problem areas (Figure 2).

The solution in that case was installingspecial casing centralizers provided byDownhole Products PLC. The central-izers were installed at every liner jointfor more than 3,280 ft (1,000 m).Characterized by a Teflon inner linerthat makes rotation less difficult andTeflon-studded spiral blades that helpthe liner slide along inside the 958-in.intermediate casing,the centralizers effectively reducedboth torque and drag and helped theoperator land the liner at TD (Figure

3). Once on bottom, the inner sleevesallowed the liner to be rotated easily

while pumping cement and during pre-cementing hole cleaning operations.

According to Kees Frederiks, seniorwell engineer, The reduced frictionpermitted the liner string to rotate atTD while cementing, greatly improv-ing the resulting cement bond quality.Effective zonal isolation is a very criti-cal success factor toward the satisfac-tory delivery of our wells, especiallythose of our smart water injectors.

Cement uniformity and bond quality

were confirmed by ultrasonic imagingtools, cement bond, and variable den-

sity logs.

Additional challengestest engineering ingenuityThe ability to construct successfullyERD wells has spurred the adaptationof other technologies to exploit thenew opportunities presented by thesewells. At Alaskas West Sak develop-ment, ConocoPhillips, together withBaker Hughes and M-I Swaco, has suc-cessfully designed, built, and installedTAML (technical advancement of mul-

tilaterals) Level 4 completions togetherwith sand management media in itsERDs.

The West Sak field lies within theKuparuk River Unit and containsbetween 7 and 9 Bbbl of oil in place.The average production rate of WestSak wells did not justify their cost, soalternative drilling and completiontechniques were implemented.Extended-reach dual-lateral wells withsand-exclusion screens were con-structed and equipped with electrical

submersible pumps (ESP). In this

application, extended reach wasdefined by the wells unwrapped bore-

hole lengths, not by the actual straight-line distance between the surface

wellheads and TD.The ability to produce two or more

reservoirs from a single mother boreusing dual lateral well constructionproved economical, and several wellshave been subsequently completedusing this technology.

In Saudi Arabias Ghawar field, SaudiAramco, Welltec, and Schlumbergerteamed up to successfully acid-stimu-late an extended-reach well using

coiled tubing (CT). One of the chal-lenges inherent with CT is lockup thatlimits its ability to reach out laterally.By applying a powerful well tractor topull the natural helical spiral profileout of the coil, engineers were able tosuccessfully negotiate 8,922 ft (2,720m) of horizontal exposed reservoir for-mation with a maximum inclination of93. While not a recent example, thiscase illustrates how complementarytechnology can overcome challengespresented by ERD well construction.

The advantages of ERD are wellknown. Constructing multiple wells todrain a large area from a single sur-face location makes economic as wellas environmental sense. The ability toreach under surface areas like cities,frozen seas, or environmentally sensi-tive areas opens valuable reservoirprospects. In fact, if it ever comes topass that the oil and gas industry ispermitted to develop the ArcticNational Wildlife Refuge, ERD will bethe technique that enables maximum

reservoir contact with minimum sur-face disturbance. Best practices willenable this work to be conductedsafely and with best results.


Figure 3. BladeRunner casing centraliz-ers use Teflon-studded blades and linersto minimize sliding and rotational fric-tion in ERD completions. (Image cour-tesy of Varel)

Copyright, Hart Energy Publishing, 1616 S.Voss, Ste. 1000, Houston, TX 77057 USA (713)260-6400, Fax (713) 840-8585


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best practices emerging for erd wells

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