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OilfieldTechnology
February
2014
Then, followedby6868gal. tail slurry
(Sp.Gr. =1.88) for cementing theannulus
zone frombottomhole to thedepthof
18701ft.
In thepast threeyears, the same
technologyhasbeenused indozens
of similarwells inHalahatangand
LunnanBlocks in theTarimBasinand
all cementing resultswerewell received
byCNPC. This technology improves the
integrityof casing stringgreatlyand
eliminates thepotential casing leaking
causedby the failureof stagecollar’s soft
sealsduringproductionperiod.
Hightemperatureandnarrowannulusliner
cementinginhorizontalwell
Well No. HA7‑XXH: For thiswell, the staticBHT is 338˚F. CNPC
drilled thehorizontalwell’s sectionbyusing thepolysulfonate
mud systemwithhigh content of chlorine, so thereare challenges
for this cementing job inannulusbetween5 in. liner and6
⅝
in.
hole:
Ì
Ì
Very high temperature, narrow annulus and irregular hole.
This jobwas finishedwell and the cementing zone is
from thebottomhole to the liner hanger’s position (depthof
20 754 ft) with the cement slurry’s Sp. Gr. of 1.50.
Hightemperaturecementingpluginsidethehorizontalliner
Well No. HA7‑XXH: After perforation and testing of HA7‑XXH,
CNPCdecided toplug theperforation zone temporarily for
futureproduction. The challenge is as follows:
Ì
Ì
Very high temperature at the cementingplugposition: 338˚F.
This jobwasalso successful andwas thefirst timeacementing
plug jobwas completedat suchhigh temperature inChina.
Conclusions
The ITACA series of cementingadditives canbeapplied toalmost
all kinds of conventional and challenging cementing jobswith
high levels of stability. Suchas: superHPHTwell cementing,
super deepwell cementing, super lone zone/one
stage cementing, super highand super lowgravity slurry
cementing. Inaddition, theseadditives are convenient toapply
becauseof the followingproperties: high salt resistanceandno
specialwater restrictions, no special restrictions to the class of
cement, only low concentrations of additives are required for
better results, they showagood linear relationshipbetween
thickening timeand thedosageof GT‑20L retarders. Furthermore,
theyareeasily formulated, showgood repeatabilityand canbe
pumped safely; theyareenvironmentally friendly, adaptableand
workwellwithother special additives.
of Gucheng X. This cementing jobwas
successfully carriedout in June of 2013
and thedesignedSp.Gr. of the cement
slurrywas 1.88. Because thewell’s depth is
23 999 ft, the static BHT is 412˚F and it is a
highpressure gaswell, so the cementing is
themost challenging job.
Characteristics
In addition to the listedCNPC required
features above, ITACA alsohas the following
characteristics:
Ì
Ì
Generic to almost all kinds of
cementing jobs.
Ì
Ì
High temperature resistance to 464˚F.
Ì
Ì
Suitability for cementing jobswith the
cement slurry’s Sp.Gr. from 0.9 to 3.0.
Ì
Ì
Low concentrations of additives allow for better cementing
results. The rheological property, fluid loss control, free
water content and compressive strength testing results are
all better than API specifications.
Ì
Ì
Excellent early strength at the bottom and top of the cement
for super lone zone cementing.
Ì
Ì
Perfect linear relationship between the thickening time and
the dosage of GT‑20L retarders.
Ì
Ì
Great stability in salt‑saturatedwater.
Ì
Ì
No special restrictions to the class of cement.
Ì
Ì
Adaptable and friendly to other special additives.
Ì
Ì
Stable performance and good repeatability, allowing for easy
formulation and laboratory evaluation.
Casestudies
Lowspecificgravityslurry,longzoneonestagecementing.
RepuXXwell inTarimBasin: For thiswell, the10
3
/
4
in. surface
casing stringwas run toadepthof 4921ft. Fromadepthof 4921ft
to22100ft, the7
⅞
in. productioncasing stringwasexposed to
the9
½
in. hole. Thusensuring thegood integrityof 7
⅞
in. casing
stringduringcomingyears’ production, CNPC requiredone stage
cementingof theannulusbetween7
⅞
incasing stringand9
½
hole,
and thecementing zone shouldbeall theway from thebottomhole
to theground. Thechallenges for this jobwereas following:
Ì
Ì
One stage cementing lengthof 22100 ft.
Ì
Ì
The staticBHT is 264˚F, so the cementingadditivesmust be
suitable forwide rangeof temperaturedifferences.
Ì
Ì
Lowgravity slurry (Sp.Gr. =1.3).
Thecement slurry’spumping sequence isas follows:
First, pumpingof 39626gal. leading slurry (Sp.Gr. =1.3) for
cementing theannulus zone fromadepthof 18701ft to theground
followedwitha small quantityof transitionary slurry.
Table2. Formulaof solidcement (446˚F)
Component
Liquidadditives’spercentage (weightof
additive/total solidphase’sweight)
Weightof cementandotheradditives (lb)
Total solid
phase’s
weight (lb)
GT‑10L GT‑20L GT‑30L GT‑66L GlassG
cement
Silica
fume
GT‑70S
GT‑600S Micro‑silicon
Figure4, 446.18˚F (230.1˚C)/
20233psi (139.5Mpa)
7.00
11.00
2.00
0.10
100
30
30
20
5
185
Figure1.
Chineseoilandgasbasins.
(Source:Energy InformantionAdministration.)
