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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
