1 PETE 411 Well Drilling Lesson 6 Drilling Structures

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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:

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/

Homework

4Standard 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 RigJack-up RigDrillshipSemisubmersibleJacket PlatformGravel Island Ice IslandGuyed TowerTension Leg PlatformSpar Platform

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Pile-founded steel jacket platform

Cost increases rapidly with depth

Bending moments

Natural Frequency

Mud Line

8 Buoyed tower concept of 1970

~100 sec nat.frequency(waves ~ 6-10 sec)

Pivot at bottom(problem)

9Principal features of the Lena guyed tower

200 TON CLUMP WEIGHTS

FAIRLEAD

19831,000 ftof water

10Arctic drilling structure - Ice Island

High ice forcesWeak soildShallow water

~1,000 ft dia.

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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 > 100 ppm

Operator must determine the H2S Concentration and the Potential Flow Rate

Radius of ExposurePoint of Escape

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H2S

Determination of Radius of Exposure

The 100 ppm radius of exposure (in ft)

6258.02100 xture) Q] in gas miion HMole fract( 589.1[R

R100= dist. from source where H2S conc. = 100 ppm

Q = source strength = open flow potential, SCFD

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H2S

6258.02500 S) Q]HFraction oleM( 4546.0[R

These are the Pasquill - Gifford Equations

The 500 ppm radius of exposure (in ft)

Determination of Radius of Exposure

R500= dist. from source where H2S conc. = 500 ppm

Q = source strength = open flow potential, SCFD

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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

0.62582500 Q]S) ion HMole Fract( 4546.0[R

6258.06 )]10*5)(1.0(4546.0[

= 2,250 ft

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Example

= 4,924 ft

6258.02100 ]Q)Sion HMole Fract( 589.1[R

6258.06 ]10*5)1.0(589.1[

ppm 500

100R500 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. > 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 > 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 > 50 ft

• and includes public area other than public road

100 ppm can cause throat irritation in < 1 hr

(ii) or R500 > 50 ft

• and includes public road 500 ppm can cause unconsciousness in < 2

min death in ~1/2 hr

(iii) or R100 > 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 notified…e.g.

• Supervisor • Hospital and Fire Dept./ Sheriff or Police• District Railroad Commission etc.• Local Residents

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Drilling Provision:

,ft000,3R100 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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Certificate must be approved before commencing activities

ft000,3R If 100

• Provide training for personnel

• Submit certificate of compliance (with all the rules)

30 days prior to commencement of drilling or WO

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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

ft000,3R If 100

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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.

What is Buoyancy?

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The End