Plug and Abandonment

Plug and Abandonment ± Producing Well  Differ Different ent from from dril drilliling ng P&A P&A opera operati tions ons..  Speci Specific fic regu regulat lation ions s set by gov gover ernin ning g bodie bodies. s.  This This prese presenta ntatio tion n cov cover ers s the ³inte ³intent nt´´ of P&A: P&A:  ± Isolate Isolate and and protect protect all all fresh and near near fresh fresh water water zones; zones;  ± Isolate Isolate and protect protect all ³commercial´ ³commercial´ producing producing horizon horizons s for future development;  ± Preven Preventt leaks leaks from from or or into into the the well; well;  ± Remove surface equipment equipment and and cut and plug plug pipe pipe below below ground ground level or, depending on requirements, mark the surface location so identification can be made at any time after abandonment.

 P&A respo responsi nsibil bilit ity y does does not not usual usually ly end end wit with h the P&A P&A activities. activities. If itit leaks, you you will likely likely have to repair repair and remediate the well and the site.  Do it right the first time.

 Abandonment Types: TA and P&A  TA ± tempo mporarily aband andoned:  ± During During a long long shut-do shut-down wn..  ± Waiting Waiting on a workov workover. er.  ± Waiting on field field developme development nt or  redevelopment. et plugs to prevent cross flow and production. Isolate all flow and protect from pressures. Monitor.

S

 Abandonment Types  P&A ± plugged an and ab abandoned:  ± End of cur curre rent nt econom economic ic opera operatio tions. ns.  ± Well problem that cannot be economically economically repaired. repaired.  ± Moving Moving the bottom bottom hole location location ± P&A the bottom bottom and reuse the top part of the well. S

et cement and mechanical mechanica l plugs to prevent cross flow and production. production. Isolate all flow and protect from pressures. pressures. Follow governing body regulations.

P&A Costs  On Shor Shore: e: noth nothing ing to low expen expense se..  ± Well equipme equipment nt recovered recovered often offsets offsets cost of P&A.

 Of Offf-Sh Shor ore: e: $10 $100k 0k to to mill millio ions ns..  ± Depends Depends on whether whether isolated isolated wells wells or whole whole campaign to decommission a platform.  ± Increased Increased by platform platform damage. damage.

Well

damage increases the P&A cost sharply ± 100k to 10¶s 10¶s of millions

Pipe damage may necessitate pulling operations not in the original plans. Cement plugs generally generally need to be circulated into place ± a functional tubing tubing string is required. Special Conditions and considerations: 1. Collapsed Collapsed or burst pipe - repair 

Legislative

Drivers

 Safe Safe Wate Waterr Dri Drink nkiing Acts cts  Numbe Numbers rs of aban abando done ned d well wells s (>3m (>3mm m in in US since 1859) and reliability of the abandonment seals.  Chan Changi ging ng reg regul ulat atio ions ns on fre fresh sh and and nea nearr fresh fresh waters.  Protec Protectio tion n of reso resource urces s for for the the futu future re (fie (fields lds are often abandoned with 60 to 80% of oil and 10 to 20% of of the gas gas still still in place) ± waiting waiting on technology development.

Main Targets  Isolation: ± open pen hol hole e,  ± separ separate ate pay zones zones,,  ± perf perfor orat atio ions ns,,  ± line linerr top tops, s,  ± surface locations (3¶ or 1m on land land to 10 to 15¶ or 3 to 5m, below ML offshore)  ± damaged sections (wear points, milling, milling, perfs, etc.),  ± multimulti-la later terals als,,  ± corrosive corrosive zones zones (highly (highly corrosive corrosive salt salt water?) water?) ,  ± special cases (clearing (clearing sea floor, rigs to reefs, reefs, geothermal, etc.).

Requirements  Plug th thickness.  Pressure te tests.  Well Well Iden Identi tifi fica cati tion on(? (?). ).  Lost radio active source tools.

Threats From Improperly  Abandoned Wells  Cont Contami amina nate ted d sur surfa face ce wate waterr entr entry y (minerals, bacteria, waste, etc.).  Surf Surface ace leaka leakage ge from from shal shallow low zones zones through well or leaking cement sheath.  Leakage form an aquifer to surface.  Leakage from surface to an aquifer.  Dang Danger er of ope open n well well to to surf surfac ace e egre egress ss (falling down the well).

Materials Used in Abandonment Abandonment      

Cemen ment slur lurries ies. Gelle Gelled d pill pills s (be (bent nton onite ite and and othe others rs). ). Spac Spacer ers s to to pro prote tect ct ceme cement nt slurr slurries ies.. Mechan Mechanical ical plugs plugs (incl. (incl. cement cement retaine retainers) rs).. Inflat latable plug lugs. Sand Sand plugs plugs (as (as bas base e for for cemen cement) t)..

P & A Concerns

Knowledge Knowledge of the the well ± where are plugs plugs needed?

Placement accuracy and efficiency of  plugs.

Reliability of the cement sheath. Reliability of the plugging system. Reliability of the uncemented casing sections.

Cement Plugs  Ceme Cemen nt slur slurry ry desi design gn..  ± Cement Cement type type and additiv additives. es.  API cl class  Extenders, Extenders, shrinkage, shrinkage, gas gas control control,, fluid fluid loss loss control, control, formation and pipe adherence, spacers.  Volu Volumes mes and and exces excesse ses. s.

 Placemen ment met method.  ± Location identification,  ± Dept Depth h con contr trol ol,,  ± Spotting method (bailer, (bailer, circulat circulation, ion, etc.),  ± Conta Contamin minat ation ion contr control, ol,  ± Testi Testing ng requi require remen ments ts..

Cement Plug Placement      

Balan lanced met method. Modif odifie ied d bal balan ance ced d met metho hod. d. Disp Displa lace ceme ment nt from from sur surfa face ce.. Two Two plu plug g cir circu cula lati tion on.. Grouting ± various. Mecha echani nica call assi assist stan ance ce..

Setting a cement plug  Position  Setting in mu mud  Effe Effect ct of fluid fluid loss loss and and cros cross s flow flow

Setting Cement Plugs  A near near 100 100% % relia reliable ble syste system m if cro cross ss flow flow can be stopped.  Most ceme cement nt plugs plugs fail fail becau because se of cross cross flow, density and viscosity mismatch, misma tch, or  failure to ³break´ the fluid momentum.  Full Full plug plug metho method d desc descri ribe bed d and and fiel field d tested in SPE 11415 (published in SPE JPT Nov 1984, pp 1897-1904) and SPE 7589.

Cement Plug Failure Many cement plugs fail for the same 4 reasons: 1. Cross Cross flow flow cuts cuts channe channels ls into into the plug plug.. 2. Cement Cement is is higher higher dens density ity that that the mud. mud. 3. The mud is is much lower lower viscosi viscosity ty than than the the cement slurry. 4. The open open ended ended tubing tubing produc produces es a high high momentum energy condition that the mud cannot stop. The result of the last three is that the cement is spread out along the hole and a plug is never  formed.

How? 1. Use a simple simple tubing tubing end plug with circulatio circulation n to the the side and upward but not downward. 2.

Spot

a heavily gelled bentonite pill below the cement plug depth. depth. Pill Pill thickne thickness ss of 500- 800 ft (152- 244 m). m).

3. Use a custom spacer spacer to separa separate te the pill and the the cement slurry. 4. Use a viscous, viscous, thixotrop thixotropic ic cement cement with with settin setting g time equal to the job time plus ½ hr. Plug thickness of 300 to 600 ft (91 to 183 m) 5. Rotate the central centralized ized tubing tubing (do not not recipro reciprocate) cate) during placement and gently withdraw at the end of  the pumping. 6.

WOC

= 4 hrs for every 1 hour of pump time.

Full details and field tests in

SPE

11415.

Diverter Plug on End of Tubing A simplified simplified diverter tool can be made by plugging the end of tubing and drilling 8 holes  ± the bottom bottom four straight straight out and and the top four  angled up at 45 o. Holes are 0.75 to 1´ (2 to 2.5 cm) diameter. diameter.

Cement Squeezes  Type Types s (so (some me name names s any anyw way) ay)  ± Bloc Block k sque squeeze eze  ± Cemen Cementt Pack Packer  er   ± Suic Suicid ide e squee squeeze ze  ± Breakd Breakdow own n sque squeeze eze  ± Running Running and Walking Walking squeezes squeezes  ± Hesitation squeeze

 Abandonment Gun Systems for  Large Casing 

Desi Design gned ed to shoo shoott thro throug ugh h one one very large diameter casing string without hitting the outer  casing string.

 ± 11.8 11.875 75´´  ± 13.3 13.375 75´´ ± 16´ 

Key Key desi design gn fact factor or:: Inex Inexpe pens nsiv ive e way to put charges near casing wall

From Phil Snider

Laying

Sand Plugs

 Shut Shut-i -in n well well for for sever several al hou hours rs to to preve prevent nt crossflow disruption of plug.  Don¶t bury th the BH A with dumped sand  Tag Tag fre frequ quen ently tly to avoid avoid overover-fil filll  Use Use a gell gell spa spacer cer in fro front nt of of sand sand to prevent sand roping or falling down the hole. Rapid sand fall out can cause bridge off inside the CT.

Sand fall rates in various fluids 10/20 mesh sand 20/40 mesh sand Fluid

ft/min

m/min

ft/min

m/min

WF220

7.5

2.3

2.2

0.67

WF240

2.05

0.62

0.49

0.15

WF260

0.49

0.15

0.11

0.03

Diesel

21.9

6.7

10.2

3.1

Water

21.9

6.7

12.6

3.8

10/20 mesh Bauxite Bauxite 20/40 mesh Bauxite Bauxite Flu id

ft/min

m/min

ft/min

m/min

WF 2 2 0

1 4 .4

4 .4

4 .1

1 .2

WF 2 4 0

4 .1

1 .2

1

0 .3

WF 2 6 0

1

0 .3

0 .2 4

0 .0 7

Die s e l

3 3 .7

1 0 .3

1 6 .9

5 .2

Wa te r

3 3 .7

1 0 .3

20

6 .1

Source ± D/S Field Field Book 

Reasons for Cement Plug Failures  Cont Contami amina natio tion n of of the the cemen cementt slurr slurry y with with drilling mud during or immediately imm ediately after  placement.  Failu Failure re to plac place e a viscou viscous s pill pill to stop stop downward movement of cement cem ent slurry.  Inac Inaccur curat ate e know knowled ledge ge of volume volumes s required.

General Requirements  Onsho nshorre ± 10 ft (3 (3 m) m) plu plug g on on top top of the the well and casing cut 3 ft (1m) below the ground surface.  Mud betw betwee een n plug plugs s (9. (9.5 5 lb/ lb/ga gal). l).  Plug Plug thic thickne kness ss minimu minimum m of 100 100 ft, ft, plus plus 10% for each 1000 ft of zone.

Procedures  Remov Remove e salva salvage geab able le equi equipme pment nt..  ± NORM NORM scale scale prese present nt? ? Leave the pipe in the well?  ± What pipe is needed needed for a barrie barrier? r? How effective?

 Set, Set, at at minimu minimum, m, plugs plugs requ require ired d by regula regulatio tions. ns. Don¶t hesitate to go beyond requirements.  Test est to to lilimits mits requ requiired. red.  Cap Cap and and iden identi tify fy as spe speci cifi fied ed..

Isolation of Open

Hole

 Cemen Cementt Plug Plug 100f 100ftt (30 (30m) m) above above and below lower-most shoe in open hole.  Cemen Cementt ret retain ainer er 50 50 to 100 100 ft (15 (15 to 30m) 30m) above the shoe. Cement 100 ft (30m) below shoe and 50 ft (15m) of cement on top.  Test Tested ed to 15, 15,000 000 lbs load load or or 100 1000 0 psi. psi.

Isolation of Perforations  Cemen Cementt Plug Plug 100f 100ftt (30 (30m) m) above above and below perfs (or to next plug).  Cemen Cementt ret retain ainer er 50 50 to 100 100 ft (15 (15 to 30m) 30m) above the perfs. Cement 100 ft (30m) below shoe and 50 ft (15m) of cement on top.  Perm Perman anen entt bridg bridge e plug plug with within in 150 150 ft (45 (45m) m) of perfs with 50 ft (15m) of cement on top.

Isolation of lap joints or liner tops.  Cemen Cementt Plug Plug 100f 100ftt (30 (30m) m) above above and below liner top (or to next plug).  Cemen Cementt ret retain ainer er or or perm perman anen entt bridg bridge e plug plug 50 ft (15m) above the liner with 50 ft (15m) of cement on top.  Cemen Cementt plug plug 200 200 ft (60m) (60m) long long wit within hin 100 100 ft (30m) of liner.

Surface Plug  On-S On-Sho hore re ± depe depend nds s on on loc local al regu regula lati tion ons. s.  Of Offs fsho hore re ± ceme cement nt plug plug 150 150 ft ft (45 (45m) m) long long within 150 ft (45m) of mud line. Placed in the smallest string of casing that extends to the mud line.

Testing of Plugs 

Location

of the first plug below the surface plug shall be verified.  ± Pipe weight weight of 15,000 15,000 lbs on on cement plug, cement retainer, or bridge plug.  ± Pump pressure pressure of 1,000 1,000 psi with with maximum maximum 10% drop in 15 minutes.

Fluid Left in the

Hole

 Fluid Fluid fill fill bet betw ween plug plugs s must must exer exertt a fluid fluid density at least higher than the greatest formation pressure in the intervals between the plugs at the time of  abandonment.