Petroleum engineering (drilling) project 2

Drilling Engineering

Class 7

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Extended Reach Drilling

• What is extended reach drilling (ERD)?

• Pertains to deviated wells

• Typically looks at the ratio of TVD vs Vertical Section

• In this class we will consider a TVD ratio of at least 2:1 as ERD • Ex: TVD= 8,000’; VS= 16,000’ or greater

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Extended Reach Drilling • 1978-1980

• Esso Australia on Mackerel Project • Wells were about 18,000’ MD • Took up to one year to drill with numerous stuck BHA’s

• 1988 • Industry started exploring ERD after rise in oil prices

• 1996 • BP successfully drills Wytch Farm well at 26,000’

• 1999 • Total drills Tierra del Fuego CN-1 at +33,000’ lateral

• First well to reach TVD ratio of 5:1 • Unocal drills offshore California C30 at 4872’ lateral (963’ TVD)

• Current record is Maersk Oil Qatar’s BD04A • 37,956’ lateral (3,500 TVD)

• Northeast Onshore Record • Utica well in OH (Eclipse Resources 2016) • 18,544’ Lateral (27,031’ MD, ~9,000 TVD)

• North American Land Record • North Slope Alaska (Conoco Phillips 2018) • 21,478’ Lateral (7,900’ TVD) • Included 2 laterals from a single wellbore

• 34,211’ combined Lateral Length • 42,993’ combined total footage

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ERD Planning

• Target formation/interval

• Point target or formation exposure?

• Well trajectory to minimize risks

• Hole Size

• Casing Plan

• Rig

• Is a bigger rig always better?

• Typically hydraulics is the limiting component

• Electrical power (top drive TQ limits, mud pump requirements)

• Solids control

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ERD Friction Factor

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Hole Cleaning

• Transporting the cuttings is extremely difficult in high angle wellbores.

• Gravity pulls downward and creates downward direction for slip velocity on the cuttings

• The mud is the carrying force on the cuttings

• In horizontal wells the mud travels horizontally in the direction of the lateral

• The cuttings will continue to fall from the top of the wellbore to the bottom

• Mud flow is not uniform throughout the cross section of the wellbore

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Hole Cleaning

• Laminar flow profile in the wellbore cross section

• There is a dead zone on the low side of the well

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Hole Cleaning

• Rotation is the key factor in hole cleaning efficiency for high angle holes

• The active flow are is at the top of the hole

• Pipe and cuttings lay at the bottom in the dead zone

• Agitation is required to “throw” the cuttings up into the fluid flow zone

• Viscous Coupling- the fluid in tension around the pipe that rotates with the drill string creating movement of cuttings to the active flow area

• Required rotary is dependent on hole size, pipe size, and ROP

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Hole Cleaning

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Hole Cleaning

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Hole Cleaning • Annular velocities create laminar flow

• Cleaning efficiencies depend greatly on geometry

• Pipe-Hole Area Ratio PHAR

• 𝑟ℎ 2 ÷ 𝑟𝑃

2 = 𝑃𝐻𝐴𝑅;

if < 3.25: small hole rules; if > 3.25: large hole rules

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Hole Cleaning

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Hole Cleaning

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