PETE 411 Well

Drilling

Lesson 6 Drilling Structures

1

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

2

Homework 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/

3

Standard Derrick - Engines close to derrick - Mechanical Transmission 4

COMPOUND 700 hp ENGINE 700 hp ENGINE 700 hp ENGINE 5

Drilling Structures:

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

6

Pile-founded steel jacket platform

Mud Line Cost increases rapidly with depth Bending moments Natural Frequency 7

~100 sec nat.frequency

(waves ~ 6-10 sec) Pivot at bottom (problem) Buoyed tower concept of 1970 8

1983 1,000 ft of water FAIRLEAD 200 TON CLUMP WEIGHTS Principal features of the Lena guyed tower 9

High ice forces Weak soild Shallow water ~1,000 ft dia.

Arctic drilling structure - Ice Island 10

11

12

Spar Platform in Transit

13

Spar Platform Installed

14

Rule 36 - TRC

 Protection of the General Public from the Effects of H 2 S  Applicable if H 2 S Concentration > 100 ppm Point of Escape Radius of Exposure  Operator must determine the H 2 S  and the Potential Flow Rate Concentration

15

H

2

S

 Determination of Radius of Exposure  The 100 ppm radius of exposure (in ft) R 100  [ 1 .

589 ( Mole fract ion H 2 in gas mi xture) Q] 0 .

6258 R 100 = dist. from source where H 2 S conc. = 100 ppm Q = source strength = open flow potential, SCFD

16

H

2

S

 Determination of Radius of Exposure  The 500 ppm radius of exposure (in ft) R 500  [ 0 .

4546 ( M ole Fraction H 2 S) Q] 0 .

6258 R 500 = dist. from source where H 2 S conc. = 500 ppm Q = source strength = open flow potential, SCFD  These are the Pasquill - Gifford Equations

17

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 H 2 S mole fraction gas mixture will be 0.1

. in the Calculate the radius of exposure to H 2 S concentrations of 500 ppm and 100 ppm .

18

Example

R 500  [ 0 .

4546 ( Mole Fract ion H 2 S) Q] 0.6258

 [ 0 .

4546 ( 0 .

1 )( 5 * 10 6 )] 0 .

6258 = 2,250 ft

19

Example

R 100  [ 1 .

589 ( Mole Fract ion H 2 S ) Q ] 0 .

6258  [ 1 .

589 ( 0 .

1 ) 5 * 10 6 ] 0 .

6258 = 4,924 ft

ppm 500 100 R 500 R 100 20

To Determine Q

 Use open flow potential  Where insufficient data exist for calculating R 100 (100 ppm radius):  Assume R 100 = 3,000 ft

21

Storage Tanks for Production

 If H 2 S conc. > 500 ppm (i) Post warning sign within 50’ facility of (ii) Fencing is required in populated area

22

Storage Tanks for Production

 In general, If R 500 > 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

23

Need Contingency Plan if:

(i) R 100 > 50 ft • and includes public area other than public road 100 ppm can cause throat irritation in < 1 hr (ii) or R 500 > 50 ft • and includes public road 500 ppm can cause unconsciousness in < 2 min death in ~1/2 hr (iii) or R 100 > 3,000 ft {600 ppm can cause death after a few minutes}

24

The Contingency Plan

 Must provide for action of alerting and protecting the public following accidental release of a potentially hazardous volume of H 2 S .

 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

25

Drilling Provision:

R 100  3 , 000 ft (i) Maintain protective breathing equipment at the well site (ii) Install and maintain automatic H 2 S detection and alarm equipment (iii) Provide means for flaring the gas

26

Drilling Provision

(iv) Provide remote control of BOP and choke equipment - at safe distance (v) DST of H 2 S zones only during daylight (vi) Notify railroad commission prior to performing such DST etc.

27

If R 100  3 , 000 ft • 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

28

If R 100  3 , 000 ft  of Altered conditions may require submittal amended certificate  Certificates are non-transferable  Completion reports for new wells must include the H 2 S conc. of the gas if in excess of 100 ppm

29

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.

30

The End

31