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Transcript
NOTICE CONCERNING COPYRIGHT RESTRICTIONS
This document may contain copyrighted materials. These materials have been made available for use in research, teaching, and private study, but may not be used for any commercial purpose. Users may not otherwise copy, reproduce, retransmit, distribute, publish, commercially exploit or otherwise transfer any material.
The copyright law of the United States (Title 17, United States Code) governs the making of photocopies or other reproductions of copyrighted material.
Under certain conditions specified in the law, libraries and archives are authorized to furnish a photocopy or other reproduction. One of these specific conditions is that the photocopy or reproduction is not to be "used for any purpose other than private study, scholarship, or research." If a user makes a request for, or later uses, a photocopy or reproduction for purposes in excess of "fair use," that user may be liable for copyright infringement.
This institution reserves the right to refuse to accept a copying order if, in its judgment, fulfillment of the order would involve violation of copyright law.
METHODS OF COMBATING LOST CIRCULATION DURING DRILLING
AND CASING CEMENTING
S. H. Shryock - D. K. Smith
H a l l i b u r t o n S e r v i c e s
ABSTRACT
The success or f a i l u r e of d r i l l i n g and complet- i n g geothermal w e l l s depends g r e a t l y on a v a i l - a b l e cementing processes. (Fig. 1) The cementing services which might be used require not only t h e selection of temperature stable competent m a t e r i a l s b u t also a complete under- s t and ing o f h o l e p r e p a r a t i o n , c a s i n g running procedures , mud displacement , los t c i r c u l a t i o n and t h e mixing-placing o f t h e cement s l u r r y . (Figs . 2-5).
Many steam f i e l d s are l o c a t e d where t h e forma- t i o n c o n t a i n s poor ly conso l ida t ed sedimentary d e p o s i t s , r u b b l i z e d s h a l e s and f r a c t u r e d vol- c a n i c rock. (F ig . 6 ) These formations a r e f r a g i l e i n t h a t some upheaval may have occurred d i s r u p t i n g t h e s t r u c t u r a l s t a b i l i t y , and, w i th l o w reservoir p r e s s u r e s , make them prime candi- d a t e s f o r l o s t c i r c u l a t i o n problems. Many of t h e geothermal w e l l s have to be d r i l l e d through and/or i n t o t h e s e f r a c t u r e d formations. Loss of d r i l l i n g mud or any other f luid p u t i n t o the ho le u s u a l l y occur s , c r e a t i n g problems which are expensive to e l i m i n a t e . This paper o f f e r s methods which have been demonstrated success- f u l i n combating l o s t c i r c u l a t i o n du r ing d r i l l i n g and c a s i n g cementing.
COMBATING LOST CIRCULATION DURING DRILLING
I f t h e h o l e is be ing d r i l l e d w i t h a 1.15 sp . . g r . mud and t h e rate o f r e t u r n becomes smaller and smaller u n t i l t h e mud loss approaches 100 bb l s per hour, t h e normal procedure i s to add l o s t c i r c u l a t i o n m a t e r i a l s to t h e mud and hope t h a t f u l l r e t u r n s can be achieved. t h i s is unsuccess fu l .
Quite o f t e n
It is decided a cementing s e r v i c e company should be c a l l e d and t h e problem d i scussed . The cement- i n g s e r v i c e company r e p r e s e n t a t i v e i s t o l d what has occur red , how deep t h e h o l e has been d r i l l e d , how long t h e r e has been l o s t c i r c u l a t i o n , and what the temperature o f t h e mud r e t u r n s have been p r i o r to l o s i n g c i r c u l a t i o n .
Normally, t h e w e l l owner is i n a hur ry and chooses to use cement because he b e l i e v e s i t can e l i m i n a t e t h e problem. I t is expected t h a t t he cementing service company w i l l b lend t h e proper materials f o r high temperatures and los t
c i r c u l a t i o n c o n d i t i o n s based on what has been t o l d them.
The d r i l l s t r i n g has been round-tr ipped t o remove the b i t and t h e cementing s e r v i c e company h a s t h e i r equipment ready t o mix and p l a c e t h e cement s l u r r y i n t h e ho le . The cement- i n g composi t ion s e l e c t e d f o r t h i s job is API Class G Cement, con ta in ing 40% sil ica f l o u r and 0.4% r e t a r d e r i n o r d e r to be able to d r i l l o u t i n 12 hours. The cement s l u r r y i s mixed a t a specific g r a v i t y of 1.86 and d i sp laced . Because it has n o t been p o s s i b l e t o f i l l the ho le , the displacement is c u t s h o r t to reduce the amount 'of mud contaminat ing t h e cement. The d r i l l pipe is t h e n p u l l e d high enough to be sure it i s above t h e cement and it is decided to w a i t 4 hours before t r y i n g t o f i l l the hole . a l l O w s t h e cement s l u r r y time t o t h i c k e n and become inore r e s i s t a n t t o flow when sub jec t ed t o a n i n c r e a s e d h y d r o s t a t i c head.
Th i s
A f t e r w a i t i n g 4 hours , an a t t empt is made to f i l l t h e h o l e ; pumping 15% more than r e q u i r e d wi thou t g e t t i n g r e t u r n s . made whether t o w a i t l onge r or do a. second job.
The d e c i s i o n t h e n has t o be
Normal practice i n geothermal w e l l los t c i r c u l a - t i o n cement p lug jobs is t o do a . s e c o n d j o b when unable t o f i l l the h o l e fol lowing t h e f i r s t job. Should t h e second j o b be done t h e same a s t h e first? L o g i s t i c s may s t r o n g l y i n f l u e n c e this d e c i s i o n as it depends g r e a t l y on what is a v a i l - able. The answer u s u a l l y is to do t h e second job i n a similar manner, only w a i t i n g longer f o r t h e cement t o set. E igh t hours fol lowing t h e second j o b , t h e h o l e i s f i l l e d and t h e d r i l l p i p e lowered t o t a g hard cement. The d r i l l p ipe is t r i p p e d o u t of t h e ho le to p i c k up t h e b i t and run t o b o t t o m . Once d r i l l i n g has resumed, it is l e a r n e d j u s t how t r eache rous lost c i r c u l a - t i o n i n geothermal w e l l s can be. r e t u r n s w i l l be los t wi th in 25 meters or l e s s ' o f where it had occur red before.
A l l too o f t e n
More and more, i t is being l ea rned t h a t l o s t - c i r c u l a t i o n i n a g e o t h e r m a l w e l l is caused by
d r i l l i n g i n t o f r a c t u r e d or broken rock. W e c a n ' t see t h e s e f r a c t u r e s and canno t p r e d i c t t h e i r size. I t is g e n e r a l l y accep ted t h a t if
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they a r e l a r g e enough to be adequa te ly s e a l e d w i t h cernent i t requires lots o f cement, and o f t e n m u l t i p l e j obs , each r e q u i r i n g 18-24 hours .
When cement has proven unsuccess fu l as a cu re €o r lost c i r c u l a t i o n du r ing d r i l l i n g or i t t akes more than one job, i t is t i m e to c o n s i d e r a new approach.
Th i s would invo lve pumping a n o t h e r material i n t o t h e ho le ahead o f t h e cement. One such m a t e r i a l i s H a l l i b u r t o n ' s Flo-Chekm chemical. The pro- cedure would then be to pump some water through t h e open-ended d r i l l pipe as n e a r t h e l o s t c i r c u l a t i o n zone as possible, fo l lowing it w i t h 25-50 b b l s o f Flo-Chekm chemical. A 5-10 bbl s p a c e r o f f r e s h wa te r shou ld fo l low t h e Flo-Chekm chemical, t hen 20-40 bbls of cement s l u r r y . Displace w i t h water u n t i l t h e Flo-Chek chemical has been d i s p l a c e d from t h e d r i l l pipe. If t h e h o l e i s on a vacuum reduce t h e pump rate, wa&ching t h e pump p r e s s u r e t o see whe-n any p res su re i n c r e a s e occurs. If a p r e s s u r e bu i ld - up occurs , pump enough water to f i n i s h dis- p l a c i n g then p u l l t h e d r i l l pipe above t h e cement and c i r c u l a t e a t a l o w p r e s s u r e to f i l l t h e hole . If r e t u r n s are ob ta ined , t h e cement needs 8-10 hours t o harden.
Probably t h e b i g g e s t advantage to u s i n g Flo-Chekm chemical has been the r e d u c t i o n i n t h e number of jobs. Using Flo-Chek chemical and cement i s a new v a r i a t i o n on methods t o combat l o s t c i r c u l a t i o n du r ing d r i l l i n g , a l though it still requires t i m e and t r i p p i n g t h e d r i l l pipe.
A t h i r d method i s suggested, which h a s been used s e v e r a l times wi th good success .
Th i s method invo lves t h e use of l a r g e volumes of f r e s h water, 10% calcium c h l o r i d e b r i n e , and Flo-Chek= chemical. Again, assuming w e have t h e same c o n d i t i o n s as p r e v i o u s l y dis- cussed, t h e procedure would be to f l u s h through t h e d r i l l pipe, wi th t h e b i t n e a r t h e loss zone o r bottom of t h e ho le , u s ing f r e s h water. Con- t i n u e pumping through t h e d r i l l p ipe 10-20 b b l s of 10% CaCl2 b r i n e fol lowed by 5 b b l s of f r e s h water, 20-40 b b l s of Flo-Chek chemical , followed by 30-50 b b l s o f f r e s h water, then mud. Main- t a i n pumping u n t i l a volume l a r q e enough to f i l l t he ho le has been pumped. I f no r e t u r n s have su r faced , pump an a d d i t i o n a l 15% volume. I f you o b t a i n r e t u r n s , resume d r i l l i n g . I f no t , do a second j o b ? u s t l i k e t h e f i r s t . Some jobs have r e q u i r e d t w o or more sequences where t h e 10 b b l s o f 10% CaC12 b r i n e , 5 b b l s o f f r e s h water , 20 b b l s of Flo-Chek chemical and 30 b b l s of f r e s h wa te r a r e r epea ted 2 t o 3 t i m e s , one behind t h e o t h e r .
The major f e a t u r e of this method is to b r i n g t h e 10% CaCl2 b r i n e and Flo-Chek t o g e t h e r i n the lo s t c i r c u l a t i o n tone , e f f e c t i n g a permanent s e a l with- o u t having to t r i p t h e d r i l l pipe or w a i t on cement. O f prime importance to t h e success o f
t he job is t h e f l u s h i n g o f t he lost c i r c u l a t i o n zone w i t h f r e s h water, then the immediate place- ment o f t h e CaC12 b r i n e and Flo-Chekm chemical.
S ince t h e d i scove ry o f Plo-Chekm chemical , t h e r e have been many v a r i a t i o n s i n t h e methods o f c u r i n g los t c i r c u l a t i o n . Some choose to run 2-3 s t a g e s o f cement and Flo-Chek chemical. O the r s run 3-4 s t a g e s o f CaCIZ b r i n e and Flo-Chek chemical, t hen cap it w i t h cement. I t i s e v i d e n t t h e r e could be a tremendous cost s a v i n g s i f t r i p p i n g t h e d r i l l pipe and wa i t ing on cement t i m e cou ld be e l imina ted . (Figure 7)
WING CEMENTING OPERATIONS (Fig. 1)
I n cementing c a s i n g , t h e o b j e c t i v e is to provide a complete f i l l up of cement i n t h e c a s i n g h o l e annulus to resist s p e c i f i c environmental con- d i t i o n s and anchor t h e c a s i n g s f i r m l y to t h e ground and to each o t h e r . The hardened m a t e r i a l should be a homogeneous, dense, impermeable body and ma in ta in that c o n d i t i o n for t h e l i f e o f t h e w e l l . I n geothermal w e l l s , t h e cement s h e a t h must p r o t e c t t h e c a s i n g a g a i n s t p o s s i b l e corros- i o n by thermal b r i n e s and h e l p p r e v e n t the uncon- t r o l l e d f l o w of thermal water and steam o u t s i d e t h e cas ing .
The main c o n s i d e r a t i o n i n des ign ing a c a s i n g program f o r steam wells i s for t h e c a s i n g to resist l o n g i t u d i n a l , t e n s i l e , and compressive f o r c e s and t h e collapse and b u r s t i n g forces t o which they may be sub jec t ed . I t was no ted i n e a r l y w e l l s that collapse or t e n s i o n f a i l u r e s o f t e n occurred 'when the c a s i n g w a s n o t properly cemented i n t h e h o l e and to t h e s u r f a c e . (Fig 81
I t appeared that c o l l a p s e f a i l u r e was caused by h e a t expansion of und i sp laced d r i l l i n g f l u i d , o r f r e e water t h a t had separated from the cement s l u r r y . a n d become confined i n pockets i n t h e annu la r space between c a s i n g s . I n more r e c e n t w e l l s , fewer f a i l u r e s have been r e p o r t e d i n a completely cemented w e l l b r e where special care has been t a k e n to e l i m i n a t e free water.
FIELD STUDIES
After r e p e a t e d l y having (I) a loss o f r e t u r n s , and ( 2 ) subsequent c a s i n g o r l i n e r f a i l u r e s , two geothermal operators examined records o f p rev ious jobs i n an a t t empt to i d e n t i f y what might be caus ing t h e s e problems. The most s i g n i f i c a n t and o u t s t a n d i n g i t e m found i n these s t u d i e s was t h e i n d i c a t i o n o f a n i n c r e a s e i n pump p r e s s u r e a t t h e cementing u n i t d u r i n g t h e displacement o f t h e cement. A f t e r f i n d i n g this on a number of p r e s s u r e c h a r t s recorded du r ing t h e cementing jobs , i t w a s dec ided t o obse rve some a c t u a l jobs to t r y and determine what might be t h e reason f o r t h e s e p r e s s u r e i n c r e a s e s and subsequent loss of re t u r n s .
On t h e l i n e r j obs , t h e i n c r e a s e u s u a l l y occurred about t h e t i m e t h e cement s l u r r y reached t h e l i n e r l a p or shoe of t h e l a s t cemented c a s i n g . Whenever
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t h e p re s su re exceeded 1.5-2 t i m e s t h e mud c i r c u l a t i n g p r e s s u r e , los t c i r c u l a t i o n oc- cu r red . On c a s i n g jobs , the i n c r e a s e might occur anytime a f t e r t h e cement s l u r r y reached t h e shoe. Observing t h e r e t u r n s where cement r e t u r n s to the s u r f a c e occur red , i t w a s no t i ced t ha t some marble s i z e c u t t i n g s were coning w i t h a f a i r l y l a r g e volume of thickened mud or mud contaminated cement. On one job, i n t h e Imperial Val ley of Ca l i - f o r n i a , the mud r e t u r n s were so t h i c k t h e y would n o t f low o u t of t h e p i t c h i n g n i p p l e t o t h e p i t . through t h e rotary table, having t h e appearance o f tree bark.
The r e t u r n s came r i g h t up
The r e s u l t s of t h e s e s t u d i e s convinced the w e l l owners t h a t t h e fo l lowing i t e m s be given e x t r a special a t t e n t i o n :
Hole Condit ions: W a s there slough- i n g , l o s t c i r c u l a t i o n , h i g h temp- e r a t u r e anomalies, caverns, h igh p r e s s u r e gas or water, s t u c k pipe, wash o u t s , etc.? What d e p t h d i d t h e s e occur? What corrective measures were taken? How much t i m e w a s s p e n t i n c l e a n i n g c u t t i n g s o u t of the hole af ter r each ing T.D.?
Casing Running Procedures: When running cas ing , do n o t exceed 400 meters per hour. a t t a c h a head t o the c a s i n g a l r e a d y i n the h o l e , and circulate for 15 minutes. This is t o clean the mud and w a l l cake away from the collars and c e n t r a l i z e r s . After the c a s i n g has reached b o t t o m , c i r c u l a t e and reciprocate a t least two ho le , vol- umes prior t o cementing.
I f the mud .v i scos i ty and t empera tu re has n o t s t a b i l i z e d , c i r c u l a t e some more.
S top eve ry 2 h r s . ,
-
F i n a l Prognosis : P r i o r t o mixing and pumping the cement s l u r r y , determine the maximum pump p r e s s u r e and do n o t exceed same. Although the d e n s i t y of t h e cement is always g r e a t e r t han t h a t o f t h e mud, t h e pump p res su re . necessary t o c i r c u l a t e t h e ho le w i t h mud can h e l p e s t a b l i s h and determine what t h e m a x i m u m p r e s s - u r e should be du r ing t h e job. If t h e h o l e w i l l c i r c u l a t e w i t h mud a t 6-10 BPM a t 800 psi , t hen i t should c i r c u - l a te w i t h cement a t a m a x i m u m p r e s s u r e o f 1200-1600 p s i w i t h a 1000 meter column.
There are many f a c t o r s a f f e c t i n g cas ing cement- i n g success . The basic o p e r a t i o n invo lves a t l e a s t t w o parties, and most o f t e n t h r e e . The s e r v i c e company p rov ides t h e pumping equipment and bulk cementing m a t e r i a l s , The w e l l owner
p rov ides t h e h o l e i n t h e e a r t h known as t he w e l l , he wants c a s i n g p rope r ly cemented i n . A d r i l l i n g c o n t r a c t o r cus tomar i ly has in - s t r u c t i o n s provided by t h e w e l l owner on what is to be done. P r i o r t o performing t h e cementing job , it i s s t r o n g l y recommended t h a t the t h r e e parties meet and d i s c u s s t h e cementing j o b and what shou ld be done by whom.
CEMENT AND ADDITIVES
The basic composition c u r r e n t l y a v a i l a b l e f o r cementing c a s i n g where temperatures i n excess o f 100°C e x i s t is API C l a s s G , ASTM Type 11, or a n e q u i v a l e n t p o r t l a n d cement with 30-80% silica f l o u r . Formulations are p repa red from ,
t h i s . b a s i c stock to meet requirements d i c t a t e d by w e l l cond i t ions , There are some 15 d i f f e r e n t t ypes o f a d d i t i v e s such as a c c e l e r a t o r s , r e t a r d e r s , d i s p e r s a n t s , f l u i d loss and b r idg ing a g e n t s commonly used i n geothermal well cement- ing. (Table 1) a d d i t i v e s t o add t o t h e b a s i c composition, it must be decided what is though t necessary to accomplish t h e job s u c c e s s f u l l y .
To de tenn ine which of t hese
The first basic need is s u f f i c i e n t f l u i d l i f e , which i s d e s c r i b e d as th i cken ing t i m e , t o p l a c e t h e cement s l u r r y i n h o l e or casing-hole annulus . Remember, this cementing composi t ion is mixed a t atmospheric c o n d i t i o n s and t h e n subjected t o h i g h e r temperatures and p r e s s u r e s i n - t h e hole . To o b t a i n t h e d e s i r e d th i cken ing time a t these h igh b o t t o m h o l e c i r c u l a t i n g temperatures , it requires a retarder be dry blended w i t h t h e cement.
It is o f t e n necessa ry t o u s e a low d e n s i t y cement s l u r r y con ta in ing b r i d g i n g agen t s to c o n t r o l l o s t c i r c u l a t i o n . S l u r r y d e n s i t y r educ t ion normally i s accomplished by adding more water . r a t i n g o u t of t h e s l u r r y , b e n t o n i t e (ge l ) is inc luded i n t h e composition.
To keep t h i s water from sepa-
Bridging a g e n t s used i n geothermal cementing compositions are e i t h e r perlites or high s t r e n g t h micro spheres . The per l i te product i s normally used a t a c o n c e n t r a t i o n o f 1 cubic f o o t per sack o f cement. The b a s i c p e r l i t e cement mix for geothermal w e l l s i n c l u d e s :
94 # 1 sack
8-10#
38X 40%
2 . 8 # 3%
0.5-1.0# 0.5-1.00
0-1 .O% 0-1.08
1 cub ic f t .
Th i s s l u r r y is mixed t o have
Cement
P e r l i t e
S i l i c a Flour
Ben ton i t e
CFR-2 Dispersant
Re ta rde r
a downhole d e n s i t y o f 1.7 kg/l . t o e a s i l y p a s s through t h e mixing-pumping equipment, y e t w i l l b r idge most formation rock f r a c t u r e s .
The perli te particles a r e s i z e d
I t i s imperative t h i s s l u r r y be mixed
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with t h e c o r r e c t q u a n t i t y o f mixing wa te r , 1 .3 cubic f e e t per 94# sack o f cement. P e r l i t e s adso rb wa te r under p r e s s u r e and, i f i n s u f f i c i e n t amounts of water a r e used, t h e s l u r r y may become too t h i c k to pump p r i o r to f i n i s h i n g the job. Using too much water can cause problems, n o t d u r i n g t h e j o b b u t once t h e w e l l has been completed and on product ion. Water which s e p a r a t e s away from t h e cement s l u r r y i s called " f r e e water." Th i s f r e e water may become t r apped and, as i t h e a t s u p , d e v e l o p s p r e s s u r e as a r e s u l t o f expansion a t t h e rate of 90 psi p e r deg ree C.
Casing and l i n e r collapse f a i l u r e s though t to have been caused from t h e presence of f r e e water t h a t e x i s t s i n s e v e r a l geothermal w e l l s i n t h e world. The newest, and p o s s i b l y t h e b e s t , cementing composi t ion to be developed f o r geothermal w e l l c a s i n g and l i n e r cementing uses what is d e s c r i b e d as h i g h s t r e n g t h micro- spheres (HSMS). I t h a s been very s u c c e s s f u l l y used i n t h e Cerro P r i e t o F i e l d s and i n o t h e r f i e l d s f u r t h e r no r th . Los t c i r c u l a t i o n and t h e n e c e s s i t y for e x c e s s cement has been g r e a t l y reduced. Cement bond l o g s have i n d i c a t e d improved bonding o v e r most o f t hese i n t e r v a l s which once caused so much d i f f i c u l t y . These f i e l d r e s u l t s s u p p o r t t h e l a b o r a t o r y o b s e r v a t i o n t h a t t h e s e type s l u r r i e s possess a n i n h e r e n t a b i l i t y to combat l o s t c i r c u l a t i o n problems by forming an e f f i c i e n t , i m o b i l e , f i l t e r cake that is r e s i s t a n t t o flow when p l a c e d a c r o s s a permeable ma t r ix . T h i s a b i l i t y , coupled w i t h good compressive s t r e n g t h development, forms a low-density s l u r r y having e x c e l l e n t thennal i n s u l a t i o n properties (D0.172 BTU/ hr-ft-OF).
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The HSMS Geothermal S l u r r y inc ludes :
94 # 1 sack Cement
38# 40% S i l i c a F lou r
3.8# 4 % Benton i t e (Gel)
Si)# HSMS Bridging Agent
5#
1.0# CFR-2 Dispe r san t
L i m e ----
0.5# H a S a e 2 2 A F l u i d Loss Addi t ive
0-1.0# HR-7 Re ta rde r
This s l u r r y is mixed to have a downhole d e n s i t y of 1.38 kg / l .
S e t t l i n g of t h e s l u r r y from t h e s u r f a c e o r having f r e e water break o u t nea r t h e s u r f a c e may al low t h e t i eback s t r i n g , which u l t i m a t e l y becomes the product ion s t r i n g , to move around a s it may be loose and unsupported f o r 10-50 meters.
The t i eback cas ing cement most popu la r ly used i n c l u d e s :
94 n 1 sack Cement
38# 40% S i l i c a F l o u r
2.8# 3% Ben ton i t e (Gel) 0.7#
0-1.0# 1% HR-7 Retarder
CFR-2 (Di spe r san t ) 0.75%
This s l u r r y i s mixed to a d e n s i t y of 1.94 kg/ l .
CONCLUSIONS
The s u c c e s s o f u s ing other methods rather than cement p lug back jobs t o combat l o s t c i r c u l a - t i o n d u r i n g d r i l l i n g cannot be overlooked. s av ings by n o t having t o round t r i p t h e d r i l l p i p e and w a i t i n g on cement time can be s e v e r a l thousand d o l l a r s .
The
Each area which has t r i e d t h e Flo-Chek@ Serv ice for l o s t c i r c u l a t i o n c o n t r o l and improving pri- mary c a s i n g cementing has followed t h e b a s i c method g iven i n this paper.
A review o f t h e primary c a s i n g or l i n e r cement- i n g s t e p s inc lude :
The h o l e has to be i n t h e best possible c o n d i t i o n prior t o running casing.
The cas ing m u s t be run s l o w enough t o h e l p p reven t f r a c t u r i n g t h e exposed formations. .
It is necessary t o s t a g e , c i r c u l a t e , and r e c i p r o c a t e w h i l e running c a s i n g f o r 15 minutes eve ry 2 hours to c l e a n t h e d e b r i s and mud cake away from t h e c e n t r a l i z e r s , collars and s c r a t c h e r s .
Once t h e cas ing is i n p o s i t i o n t o cement, c i r c u l a t e a t least t w o ( 2 ) ho le volumes while r e c i p r o c a t i n g t h e cas ing to c l e a n t h e h o l e f u r t h e r and t o cond i t ion t h e mud.
Check t o be s u r e you have t h e c o r r e c t amount of materials, equipment, and manpower t o perform the job.
B e s u r e t h e r e i s an adequate volume of s u i t a b l e cement mixing wa te r a c c e s s i b l e to the cement mixing- pumping u n i t s .
E s t a b l i s h a maximum pump p r e s s u r e n o t t o be exceeded. --- Mix and pump t h e f l u s h , s p a c e r , Flo-Chek'" chemical, cement s l u r r y , p lugs , and displacement f l u i d s i n
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t h e i r correct sequence a t the m a x i m u m rate p o s s i b l e wi thou t exceeding the predetermined maximum pump p r e s s u r e .
(9 ) Once the p lug h a s bumped, check the floats. If they are n o t ho ld ing , close i n t h e head b u t monitor t h e i n s i d e cas ing p r e s s u r e and bleed it off whenever it b u i l d s up t o more t h a n 200 psi ove r t h e equali- z a t i o n p res su re .
(10) W a i t a t least 20 hours for t h e cement t o harden prior t o d i s t u r b i n g it.
REFERENCES
1. Messenger, Joseph U. : "Lost C i r c u l a t i o n , 'I PennWell Books, Tulsa, OK.
2.' Smith, Dwight K.: SPE Monograph.
3. Howard, G. C., and P. P. S c o t t , Jr.: "An Analys i s and t h e Con t ro l of Lost Circu- l a t i o n , " Trans. AIME, 1951, p. 171.
4 . Lummus, J. L. : "A New Look a t Lost C i r c u l a t i o n , 'I Petroleum Engineer, (Nov. 19671, pp. 69-70, 72-3.
5. Goins, W. C. Jr. : "How t o Combat C i r c u l a t i o n Loss," O i l & G a s Jou rna l (June 9 , 1952) pp. 71-92.
6. Ga l lus , J. P., Pyle , D. E., and Watters, L. T.: "Performance of O i l W e l l Cement- i n g Compositions i n Geothermal Wells," SPE 7591 p resen ted a t t h e 53rd Annual F a l l Meeting i n Houston, TX.
7. Ga l lus , J. P., Pyle, D. E . , and Moran, L. K.: "Phys ica l and Chemical Proper- t i e s of Cement Exposed t o Geothermal Dry Steam," SPE 7876 p resen ted a t t h e 1979 SPE Meeting i n Houston, TX.
8. C la rk , C. R., and Carter, L. G . : "Mud Displacement wi th Cement S l u r r i e s , J. Pe t . Tech. ( Ju ly 1973) 775-783.
9 . Haut, R. C . , and Cook, R. J.: "Primary Cementing, The Mud Displacement P rocess , " SPE 8253, 1979 F a l l Meeting i n L a s Vegas, Nevada.
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TYPICAL PRIMARY CEMENTING JOB
1-Plug container-,. :.
2 - B u I k rn a t e r la I &'stOia g e: u n It ._ . .'!- ' . .
From Advancement in Cementation Techniqges in the Italian Geothermal Wells by Cigni, Ugo, Fabbri, Fulio, Grovannoni. Anselmo - Larderello. Italy
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imperial Valley Wel ls Current
Surface Casing
16" - 20" hole Set to -c 100 feet
Intermediate Casing
I 33/8" - I ~ ' / z ' ' hole Set = 1200 feet
Production Casing
95.8" - 1 21/4'f hole Set 2 8000 feet or deeper
6HST"F 450" - 550°F
G Cement Flour
API Class G Cement 1 cu f t Perlite 3% Ben~onite Friction Reducer Fluid Loss Agent Retarder
Stage Cement Tool (2-3 stages) location based on fracture gradient
API Class G Cement 1 cu f t Perlite 3*20 Bentonite 40% Silica Flour Friction Reducer Fluid Loss Agent Retarder (8asic ce~en t ing co~posit ion used on both stages of production st ring)
Note - All slurries should be mixed with 0% free water.
FIGURE 3
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Conductor Casing 20" - 26" hole Set at 100-150 feet
Surface Casing
133/~'f - 17W' hole Buttress thread Set at 2000 - 2500 ft K-55 - 61 ppf
Production Liner
9%" - 12%" hole Buttress thread
Set at 5000 - 5800 ft 36-40ppf .
Open Hole
8 3 i 4 to 7000 - 10,000 feet BHST 450-525°F
Northern California G e y s e r s Area
Intermediate
API Class G Cement 35% Silica Flour 1 cu ft Perlite 3% Bentonite Friction Reducer .
7
Liner - Lead Slurry
API Class G Cement 40% Silica Flour 1 cu ft Perlite 3% Bentonite Friction Reducer Retarder
Tail In Slurry
API Class G Cement 40°/0 Silica Flour Friction Reducer Retarder
Note - Liner top sometimes squeezed tie back string usually 10V4". All slurries mixed with 0% free water. Preflushes used on all strings.
Fitler Additive Friction Reducer ~ e n ~ o n i ~ e Fluid Loss Agent
I
Friction Reducer Fluid Loss Agent Retarder
API Class G Cement 40% Silica Flour Fitter Additive Friction Reducer Bentonite Fluid Loss Agent
Note - Flushes ahead of cement slurry on surface and intermediate strings.
FIGURE 5
80-
I \ -
F I G U R E 6
TYPES
Natura l f r a c t u r e s and f a u l t s So lu t ion c a v i t i e s and caverns Extended vugs - honeycomb Unconsolidated sand and g rave l s Highly permeable formations Pressure s e n s i t i v e bedding planes F rac tu res induced by pressure surges
SOLUTION
Locate i n t e r v a l Apply c o r r e c t i v e measures
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Hot water, steam
FXGUFE 8
CASING BUCKLING OF UNSUPPORTED PIPE W I T H HEATING
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TABLE 1 S ~ ~ ~ A R Y OF OILWELL C E ~ E ~ T ~ ~ G A~DIYIVES'
Use Chemical Comoosition Benelit T V D ~ of Cement Type 31 Additive Accelerators
~-
Reducing WOC time Setting surface pipe Setting cement plugs Comba~ing lost circula~ion
Accelerated setting High early strength
Ail APl Classes Pozzolans Diacel systems
Calcium chloride Sodium chloride Gypsum Sodium silicate Dispersants Sea water
Retarders Increasing thickening time for placement
