PETE 411 Well Drilling

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PETE 411 Well Drilling

• Lesson 6
• Drilling Structures

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Types of Drilling Structures

• Conventional Rotary Rig for drilling on Land
• Alternate Drilling Structures
• Structures for deep Water or Arctic Drilling
• Hydrogen Sulfide and RULE 36

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Read
Homework

• Applied Drilling Engineering, Ch.5 (bits)
• HW 3 Posted (due Sept. 18, 2002)
• Find HW 3 and Lessons at
• http//pumpjack.tamu.edu/juvkam-wold/

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Standard Derrick - Engines close to derrick -
Mechanical Transmission
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700 hp ENGINE
COMPOUND
700 hp ENGINE
700 hp ENGINE
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Drilling Structures

• Conventional Land Rig
• Jack-up Rig
• Drillship
• Semisubmersible
• Jacket Platform
• Gravel Island
• Ice Island
• Guyed Tower
• Tension Leg Platform
• Spar Platform

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Pile-founded steel jacket platform
Cost increases rapidly with depth
Bending moments
Natural Frequency
Mud Line
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100 sec nat.frequency (waves 6-10 sec)
Pivot at bottom (problem)
Buoyed tower concept of 1970
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1983 1,000 ft of water
FAIRLEAD
200 TON CLUMP WEIGHTS
Principal features of the Lena guyed tower
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High ice forces Weak soild Shallow water
1,000 ft dia.
Arctic drilling structure - Ice Island
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Spar Platform in Transit
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Spar Platform Installed
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Rule 36 - TRC

• Protection of the General Public from the
  Effects of H2S
• Applicable if H2S Concentration gt 100 ppm
• Operator must determine the H2S Concentration
• and the Potential Flow Rate

Point of Escape
Radius of Exposure
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H2S

• Determination of Radius of Exposure
• The 100 ppm radius of exposure (in ft)

R100 dist. from source where H2S conc. 100
ppm Q source strength open flow potential,
SCFD
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H2S

• Determination of Radius of Exposure

• The 500 ppm radius of exposure (in ft)

R500 dist. from source where H2S conc. 500
ppm Q source strength open flow potential,
SCFD

• These are the Pasquill - Gifford Equations

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Example

• A well that is about to be drilled is estimated
  to have an open flow potential of 5 million SCFD.
  Based on other wells in the field it is
  estimated that the H2S mole fraction in the gas
  mixture will be 0.1.
• Calculate the radius of exposure to H2S
  concentrations of 500 ppm and 100 ppm.

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Example
2,250 ft
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Example

• 4,924 ft

ppm 500 100
R500 R100
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To Determine Q

• Use open flow potential
• Where insufficient data exist for
  calculating
• R100 (100 ppm radius)
• Assume R100 3,000 ft

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Storage Tanks for Production

• If H2S conc. gt 500 ppm
• (i) Post warning sign within 50 of facility
• (ii) Fencing is required in populated area

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Storage Tanks for Production

• In general, If R500 gt 50 ft
• (i) Post warning signs on access roads
• (ii) Post marker signs at public crossing
• e.g. Poison Gas and Caution
• in Black and Yellow colors

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Need Contingency Plan if

• (i) R100 gt 50 ft
• and includes public area other than public road
• 100 ppm can cause throat irritation in lt 1 hr
• (ii) or R500 gt 50 ft
• and includes public road
• 500 ppm can cause unconsciousness in lt 2
  min death in 1/2 hr
• (iii) or R100 gt 3,000 ft
• 600 ppm can cause death after a few
  minutes

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The Contingency Plan

• Must provide for action of alerting and
  protecting the public following accidental
  release of a potentially hazardous volume of
  H2S.
• Plan must include (names and) phone numbers
  of people to be notifiede.g.
• Supervisor
• Hospital and Fire Dept./ Sheriff or Police
• District Railroad Commission etc.
• Local Residents

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Drilling Provision
If we also need to
(i) Maintain protective breathing equipment at
the well site (ii) Install and maintain
automatic H2S detection and alarm
equipment (iii) Provide means for flaring the
gas
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Drilling Provision

• (iv) Provide remote control of BOP and choke
  equipment - at safe distance
• (v) DST of H2S zones only during daylight
• (vi) Notify railroad commission prior to
  performing such DST
• etc.

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• Provide training for personnel
• Submit certificate of compliance (with all
  the rules)
• 30 days prior to commencement of drilling or
  WO

• Certificate must be approved before commencing
  activities

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• Altered conditions may require submittal of
  amended certificate
• Certificates are non-transferable
• Completion reports for new wells must include
  the H2S conc. of the gas if in excess of 100
  ppm

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What is Buoyancy?

• Buoyancy is the net effect of all the pressure
  forces acting on a submerged body.
• The buoyancy force is equal to the weight of
  fluid displaced.
• For example, a one-cubic-ft rock submerged in a
  tank containing water would experience a
  buoyancy force equal to the weight of 1 cu. ft
  of water, i.e., 62.4 lbf.

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The End