1979 devonian shale.pdf

8/10/2019 1979 Devonian shale.pdf

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A WELL LOG METHOD FOR ,

EVALUATI NG THE DEVONI AN SHALES

I N THE APPALACHI AN BASI N

J ohn B. Cur t i s and W Geor ge Fi ngl eton

Sci ence Appl i cat i ons, I nc.

Pr epared f or t he

Uni t ed St at es Depart ment of Ener gy

Morgant own Energy Technol ogy Cent er

East ern GUS Shal es Proj ect

Under Cont r act No. EY- 78- C- 21- 8216 Task 09

J anuar y 8, 1979


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ABSTRACT

The Devoni an Shal e f ormati ons of t he Appal achi an, I l l i noi s, and M chi gan

Basi ns are bei ng st udi ed by t he Morgantown Energy Technol ogy Center

( U. S. Depart ment of Ener gy) and i ndust r y ( East ern Gas Shal es Pr oj ect )

i n order t o accel erate t he devel opment of t he natural gas pot ent i al

of t he shal es.

Tot al gas resour ce est i mates f or t he Appal achi an Basi n

al one r ange f r om 3 t o 2400 TCFG.

Al t hough r el ati vel y compl ete wel l l og sui t es have been r ecor ded i n

wel l s dri l l ed f or charact er i zati on and st i mul at i on resear ch experi ment s,

t he Devoni an Shal e i s an unconventi onal gas resource and t he reservoi r

i s not r eadi l y eval uated by convent i onal wel l l og anal ysi s. The

econom cs of shal e wel l s and the sensi t i vi t y of t he shal es t o dri l l i ng

muds r equi r e t hat an operat or be abl e t o eval uat e a wel l usi ng a m ni mum

of wel l l ogs, pr ef erabl y r ecor ded i n an empt y bor ehol e.

Log sui t es r ecor ded i n empt y and l i qui d- f i l l ed bor ehol es have been

anal yzed f rom a t ot al of seven wel l s i n t hr ee st ates i n t he Appal achi an

Basi n.

Several t echni ques were at t empt ed t o i dent i f y gas- and kerogen-

ri ch and nat ural l y f ractured i nterval s, i ncl udi ng constr ucti on of

resi sti vi t y and porosi t y overl ays, cal cul at i on of Producti on I ndi ces, ,

anal ysi s of t emperature,

bul k densi t y compensati on and Si bi l ati on,

curves.

The i nformati on ext r acted f r om t he l ogs was compared to

convent i onal core desor pt i on ( off gas) , f r acture and geochem cal

data as wel l as t o comput er- generated synergeti c l ogs. A sui t e of

empt y- borehol e l ogs has been def i ned whi ch wi l l yi el d maxi mum f ormati on

eval uat i on dat a at a m ni mum cost .

' Trademarks of Bi r dwel l


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OpenFi l eNo. 144

CONTENTS

Abstract

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

i

I nt roduct i on

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1

Obj ect i ves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1

Techni ques and Theory

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2

Di scussi on of Resul t s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Sunmary of Observat i ons

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

21

Recommendat i ons

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

21

Ref erences

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

23

Appendi x A

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

A- l


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. .

I NTRODUCTI ON

i

. I

Si nce t he i ni t i at i on of t he East er n Gas Shal es Proj ect ( EGSP) i n

1975, rel at i vel y compl ete r esearch sui t es of geophysi cal wel l l ogs

have been r ecorded i n EGSP- sponsor ed wel l s.

Anal ysi s of t he wel l l ogs i s extremel y di f f i cul t si nce t he

Devoni an Shal e r eservoi r i s an unconventi onal reservoi r and t he

r esponse of t he l oggi ng sondes t o t he kerogen, f r act ure syst ems and

encl osi ng shal e matr i x i s i nadequat el y underst ood. There are no

publ i shed chart s or nomogr ams avai l abl e f or i nt erpr etat i on of t he wel l

l og si gnatures, so l og anal ysi s must be conduct ed by compar i ng anomal ous

and/ or potenti al l y pr oduct i ve zones wi t h known pr oduct i on/ show, of f gas

and f r acture dat a.

The l og anal ysi s seeks t o i dent i f y f r act ures i n

conj unct i on wi t h gas- ri ch shal e zones.

Sporadi c anal yses of some of t he EGSP wel l s has been per f ormed

by Col umbi a Gas System Servi ce Cor porati on ( Sm t h, 1976) , Bi r dwel l

Di vi si on of Sei smogr aph Servi ce Corporat i on ( Myung, 1976) and

Schl umberger ( Hi l t on, 1977).

A nor t her n Ohi o and t wo Li ncol n County,

WV wel l s ar e t he onl y wel l s f or whi ch detai l ed l og anal yses are

avai l abl e, even t hough sever al years have el apsed si nce other wel l s

were dri l l ed and l ogged.

The anal yt i cal approaches t aken by t he t wo l oggi ng ser vi ce compani es

natural l y f avor t hei r respect i ve . propri et ar y l oggi ng tool s and t echni ques.

A pr act i cal l og sui t e must be def i ned f or t he Devoni an Shal es whi ch

opt i m zes t he amount of f ormati on eval uat i on i nf ormati on gai ned i n vi ew

of l oggi ng and r i g t i me costs.

EGSP r esearcher s of t en hear t he st atement

t hat onl y a gamma r ay, bul k densi t y,

resi st i vi t y, t emper at ure and a noi se

l og are requi r ed, but t here has been no pr evi ousl y publ i shed proof t o

ver i f y the st atement .

OBJ ECTI VES

Sci ence Appl i cat i ons,

I nc. ( SAI ) under t ook t hi s study wi t hi n t he

Appal achi an Basi n wi t h f i ve obj ecti ves i n m nd. The Appal achi an Basi n

was chosen si nce t he great est amount of dat a were avai l abl e.


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OpenFi l eNo, 144

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si m l ar l i t hol ogy, and t he neut r on and densi t y cur ves wi l l r espond i n

oppost t e di r ect&ns due t o t he f act t hat t he neut r on tool ~111 respond

' +?#W@ ng a f al se l ow porosi t y whi l e the bul k densi t y

c&s- hi gh porosi t y.

Temper ature l ogs r espond to gas l eaki ng f r om a f r actur e system i nt o

a borehol e by r ecor di ng a cool i ng eff ect on t he wel l ' s geot hermal

t emper atur e gr adi ent , near t he poi nt of gas ent r y. A more sophi st i cat ed

appr oach i nvol ves t he cal cul at i on, by comput er, of J oul e- Thompson

Coef f i ci ent s and r esul t ant pr edi ct i on of t he degr ee of natur al f r acturi ng,

by cal cul ati on of a f r actur e i ndex (Myung and Cal dwel l , 1977) . A

qual i t ati ve i ndi cati on of f r actur i ng i s der i ved t hr ough t he equati ons

and t echni ques i n t he ci t ed r efer ence.

Both t ypes of t emper at ure dat a

wer e avai l abl e f or st udy.

3. Si bi l at i on ( Dry- Hol e)

Si bi l at i on l oggi ng, as r ef err ed to i n t hi s report , i s a t rademark

of t he Bi r dwel l Di vi si on of Sei smogr aph Servi ce Corpor ati on.

The tool

r esponds t o several f r equency bands of "noi se" and i s abl e to l ocat e,

by sound detect i on, t he escape of gas f r om a f r actur e i nt o a borehol e.

I t i s i mpor t ant t o r eal i ze t hat bot h Si bi l ati on and t emperature l oggi ng

wi l l i ndi cate t he pr esence of f r actures onl y i f gas i s pr esent i n t he

f r act ur e and t he f r act ur e communi cat es wi t h t he borehol e.

4. Resi st i vi t y Cur ve Over l ays ( Dr y and Net- Hol e)

I n a si m l ar f ashi on to t he por osi t y t ool s, t he cur ves r ecor ded

by r esi st i vi t y devi ces wer e over l ai d and anal yzed. The r esi st i vi t y

t ool s empl oyed have di f f er ent dept hs of i nvest i gati on, i . e. a t ool may

r ead onl y t he r esi st i vi t y of t he mudcake, or t he f ormati on i mmedi atel y

adj acent t o t he borehol e, or i t may r ead var yi ng di st ances i nt o t he

f or mati on.

The net r esul t i s t hat some shal l ow- r eadi ng r esi st i vi t y

devi ces ( Laterol og, , Fl i crol aterol og, ) . wi l l respond to vert i cal , mud- f i l l ed

f r actur es, whi l e deeper- r eadi ng i nduct i on t ool s wi l l not r espond and

wi l l read a hi gher val ue of resi sti vi t y. I deal l y, t he cur ve separati on

wi l l be apparent i n a f r actur ed i nt erval , whi l e the cur ves wi l l not

separat e as much and wi l l t r ack each other i n a non- f r actur ed i nt erval . .

Thi s t echni que i s a "qui ck- l ook" method and must be used wi t h car e and

i n conj unct i on wi t h other t echni ques.

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1

Tr ademar ks of Schl umberger


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5.

Pr oduct i on I ndi ces ( Dr y Hol e)

Product i on I ndi ces ( PI ) as ref er red t o i n t hi s paper are a devel op-

ment of Dr . J ohn I . Myung of Bi r dwel l Di vi si on of SSC. ( Myung, 1976) .

Potenti al pay zones and f r act ur i ng may be i ndi cated by an i ncr ease

i n gamna- r ay i nt ensi t y and resi st i vi t y due t o t he pr esence of kerogen,

other organi c matt er, and gas- f i l l ed f r actures and an accompanyi ng decr ease

i n bul k densi t y due to the l ower bul k densi t y of ker ogen and/ or t he

pr esence of f r actures whi ch woul d appear as i ncreased porosi t y.

Thi s r el ati onshi p, t he Pr oduct i on I ndex, may be expr essed mathe-

mati cal l y as

Pr oduct i on I ndex ( P. I . ) = G_ + R

1

"b

Where: G = API uni t s f r om qamma r ay l og

Aver age API uni t s of Shal e

. I

t

R=

1

Resi st i vi ty fr om i nducti on l og

Average Resi st i vi t y of Shal e

Db

= The bul k densi t y val ue f r om a Densi t y Log

The aver age val ues must be chosen f or each wel l . Pr oduct i on I ndi ces

f or thi s st udy were cal cul ated on t wo f oot i nt erval s. The P. I . may be

pr oport i onal l y r el ated to t he number of gas pr oduct i ve f r actures i n a

shal e formati on ( Myung, 1976) .

Pr oduct i on I ndi ces were cal cul ated f or f i ve of "t he seven wel l s. The

r emai ni ng t wo wel l s had t he I ndi ces pr evi ousl y cal cul ated by Bi r dwel l

on t hei r Cor n- Pr o Log2.

6. Del t a Rho ( Dr y Hol e)

The f i nal t echni que empl oyed i n t hi s st udy was to anal yze t he del t a

r ho or bul k densi t y compensat i on curve to l ocate zones wher e t he

compensat i on i ncreased whi l e t he cal i per showed a uni f orm borehol e. The

i ncr ease i n compensat i on may be due t o t he ef f ect s of f r acturi ng

communi cat i ng wi t h t he borehol e.

I f t he cal i per i ndi cates a washed out

borehol e and t he compensat i on i ncr eases, a f r act ur e syst em may be pr esent .

and the borehol e may be washed out as a r esul t of t he f r act ure.

Because

of t hi s ambi gui t y,

t he del t a r ho t echni que i s a "qui ck- l ook" method and

2

Trademark of Bi r dwel l Di vi si on of Sei smogr aph Servi ce Corpor ati on

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Open Fi l e No. 144

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not a f i rm i ndi cator of f ractur i ng.

/

.

Al l si x of t hese techni ques were appl i ed t o al l of t he st udy wel l s,

i f t he l ogs had been recor ded.

As pr &i ousl y st ated, t he l og anal ysi s of t he Devoni an Shal es must

compare l og data to knownf r actur e, pr oduct i on and of f gas data i n

order t o i dent i f y the l og si gnatur e f or f ract ured, gas- ri ch zones.

Thi s st udy empl oyed data f r om Col umbi a Gas Servi ce Tr ansm ssi on

Corpor ati on ( Ranost aj , et al , 1976), t he cont i nui ng mont hl y and quart erl y

r eport s of data gener at ed by Bat t el l e Col umbus Laboratory and Mound

Faci l i t y, r epor t s compi l ed by DOE/ METC ( Byrer, et al , 1976; Komar, et al ,

1978) and SAI ( Kucuk, et al , 1978) and f r actur e dat a generat ed by C. S.

Dean and B. Kul ander ( Dean, 1979) .

The eval uati on of t he ut i l i t y of each of t he si x pr evi ousl y ment i oned

t echni ques was determ ned by anal ysi s of wel l l ogs f r om t he f ol l owi ng

wel l s:

Col umbi a Gas #20337, Mar t i n County, KY

Col umbi a Gas #20338, W se County, VA

Col umbi a Gas #20401, Li ncol n County, WV

Col umbi a Gas #20402, Li ncol n Count y, WV

Consol i dat ed Gas #11940, J ackson County, WV

Consol i dat ed Gas #12041, J ackson County, WV

I

Reel Energy D/ K Farm # 3, Mason Count y, WV

A di scussi on of each techni que' s uti l i ty f ol l ows.


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OpenFi l eNo. 144

DI SCUSSI ON OF RESULTS

Each of t he si x anal yti cal t echni ques are di scussed separatel y.

The uni f or m t y or non- uni f orm t y of the resul t of each t echni que i s .

compar ed among t he st udy wel l s. Each t echni que i s compar ed to

pr oduct i on, core f r act ur e, of f gassi ng, and carbon cont ent data wher e

i t i s avai l abl e.

Support i ng f i gur es are pr esented f or each t echni que.

These f i gur es are i ntended t o demonst r ate what t he expect ed cur ve

r esponses shoul d be i n a gas- f i l l ed f r acture system and what r esponses

were act ual l y observed i n t he st udy.

Exampl es f r om t he st udy wel l s were chosen f or di scussi on of each

t echni que. The wel l l og anal ysi s r esul t s for al l t he st udy wel l s are

pr esent ed i n Appendi x A.

Porosi t y Cur ve Over l ays

Thi s t echni que i nvol ved t he compari son of acoust i c, neut r on porosi t y,

and bul k densi t y curves.

Thi s anal ysi s was perf or med to determ ne i f

secondary por osi t y ( f r actures) and gas accumul ati on coul d be i dent i f i ed

i n t he shal es. Secondary por osi t y m ght be i ndi cated by a const ant

acoust i c por osi t y r eadi ng t hr ough an i nt erval whi l e t he neut r on and bul k

densi t y curves i ndi cat e hi gher por osi t y val ues through that i nt erval .

Gas accumul at i on may be i ndi cat ed by an anomal ous curve def l ect i on t oward

l ower porosi t i es i n t he neut r on cur ve and a def l ecti on t oward hi gher

porosi t y i n t he bul k densi t y and acoust i c curves. Fi gur e 1 i s an

exampl e of t he "gas ef f ect " on t hese curves i n a sand- si l t i nt erval .

The anal ysi s f or secondary porosi t y was per f ormed on t hr ee of t he

seven wel l s ( DK#3, #20402, and #20401) .

These t hree wel l s were t he onl y

wel l s wi t h a compl ete sui t e of acoust i c,

neut r on, and bul k densi t y curves.

No zones were f ound i n whi ch t he acoust i c curve r emai ned const ant and

t he neut r on/ bul k densi t y cur ves i ndi cated hi gher por osi t i es. For exampl e,

natural f r actures were i dent i f i ed t hr ough core exam nati on of t he D/ K 83

wel l i n t he i nt erval 2859- 2875 f eet . ( Dean, 1979) . Through thi s i nt erval ,

t he t hr ee porosi t y curves show no r esponse t hat woul d i ndi cate secondary .

porosi ty ( f ractures).

Fi gure 2 shows t hi s i nter val and t he r esponse of

t he cur ves.

The absence of curve si gnat ur es i ndi cat i ng the pr esence of

f r actures was t ypi cal t hr oughout t he D/ K#3 wel l and t he other t wo wel l s.

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GAMMA RAY

OpenFi l eNo. 144

NEUTRON

DEPTH

-

2160

-

2170

-

2180

-

2190

-

2260

-

2210

-

2220

-

2230

-

2240

;-

2250

-

2260

Fi gur e 1.

Wel l #20337 showi ng a t ypi cal exampl e of curve

def l ecti on ( "gas ef f ect" ) on t he neut r on and

bul k densi t y curves i n a sand- si l t zone.

7

_ _.--.

.~._ ___ __ ._-.--.~---- .---


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OpenFi l eNo. 144

GAMMA RAY

y_l

DEPTH

2840

2850

2 860

2870

2880

2890

2900

NEUTRON

ACOUSTI C

BULK

POROSI TY

At

DENSI TY .

INCREASiNG

ll$REASING

INCREAS l_NG

---

Fi gure 2.

Wel l D/ K#3 showi ng an exampl e of how por osi t y

curve over l ays do not r espond to i ndi cat e a

zone of known f r act ur es.

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Open Fi l e No. 144

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Si x of t he seven st udy wel l s were anal yzed f or the ef f ect of gas

on t he neutr on and bul k densi t y cur ves. Wel l # 12041 di d not have a

neut r on perasi t y survey r un so i t coul d not be i ncl uded i n t he anal ysi s.

Wel l s #2n33f and t 11940 were t he onl y t wo wel l s wher e t he anomal ous

r *. r

def l ecti on ( gas eff ect) of t he por osi t y cur ves was observed i n t he shal es.

I n Wel l 620337 thr ee zones ( 2530- 2610 f eet, 2758- 2904 f eet, and 3094- 3267

f eet) and i n Wel l #11940 t wo zones ( 3426- 28 f eet and 3450 f eet) were

i dent i f i ed as exhi bi t i ng t he anomal ous def l ect i on.

Fi gur e 3 i s an

exampl e of thi s def l ect i on i n Wel l #20337. The i nt erval 3094- 3267 f eet

i n Wel l #20337 was st i mul ated, but t he af t er st i mul ati on data was not

avai l abl e.

110 ot her i nt er val s di spl ayi ng t hi s ef f ect wer e st i mul at ed.

Exam nati on of t he core f r om Wel l #11940 f ound one f r acture i n or near'

each of t he t wo zones showi ng the "gas ef f ect " on t he curves.

No cor e

was t aken i n Wel l 820337.

I f t he anomal ous def l ecti on of t he por osi t y cur ves observed i n

Wel l s #20337 and #11940 i s real l y t he resul t of gas accumul ati on i n

f ractures, i t i s di f f i cul t t o expl ai n why thi s ef f ect was not observed

i n any of t he ot her wel l s.

Thi s probl em cert ai nl y warr ant s f urt her

consi derat i on.

Temperat ure Curves

Temperat ure surveys ar e uti l i zed t o i dent i f y zones where t he

l i berat i on of gas i nt o t he borehol e resul t s i n a cool i ng eff ect

( t emperat ure ki cks) . I t i s general l y bel i eved that t he gas i s rel eased

t hr ough f r actur es t hat ar e i n communi cat i on wi t h the borehol e.

Anal ysi s of t emperat ure curves was perf ormed on al l seven st udy wel l s.

Two of t hese wel l s ( #20337 and #20402) had comput er gener at ed J oul e- Thompson

Coef f i ci ent s t hat were used t o deri ve a t hermal f r acture i ndex. Thi s

i ndex i s used as a r el ati ve i ndi cator of f r acture si ze based on t he degr ee

of cool i ng of t he gas ent eri ng t he borehol e.

I t i s obvi ous t hat i nspecti on of t he t emperature cur ve can gi ve t he

qui ckest i ndi cati on of gas accumul ati on i f i t i s i n communi cati on wi t h t he

bor ehol e.

I n many cases, a "c ool i ng ki ck" on t he t emperature curve was

t he onl y cri t er i a used f or sti mul ati ng an i nt er val . I n Wel l #20337, t he

zone f rom 3526 t o 3574 f eet was i nvest i gat ed. Anal ysi s of al l avai l abl e

l ogs and appl i cati on of t he t echni ques of t hi s st udy over t hi s zone

showed i ndi cat i ons of gas accumul ati on and f r actur i ng as evi denced by a

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GpenFUeHo. 144

i .

GAMMA RAY

I

[ API UNI TS1

I NCREASI NG

1

:

-4

: Z,

.

.

3

,

.

DEPTH

Fr 2520

-/1 2530

32

2630

NEUTRON

BULK

POROSITY

DENSITY

J 4CREASI NG .

I NCREASI NG

- -

Fi gure 3. Wel l #20337 showi ng an exampl e of cur ve def l ect i on

.

( possi bl e "gas ef f ect" ) on t he neut r on and bul k

densi t y curves i n a shal e zone.

10

-.._

_-...- .


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Open File I-JO.44

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j

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" cool i ng ki ck" on t he t emperature cur ve.

Based on t he t emper at ure ki ck

and possi bl e Si bi l ati on ki ck,

t he zone was st i mul ated ( Fi gure 4) . Bef ore

st i mul at i on pr oduct i on was zero MCFG/ day and af t er st i mul at i on was 133

bt CFG/ day.

.

T

The' t emperature cur ve i s a good tool f or t he anal ysi s of t he shal es

. r as l ong as t he nat ural f r act ur es ar e i n communi cat i on wi t h t he borehol e.

. a

: +J

=-

I n one st udy wel l , #20338, i nspect i on of t he t emper ature curve showed

,.::j

o obvi ous " cool i ng ki cks" yet t wo zones were s t i mul ated ( 4890- 4910 f eet

i .

.l

7

and 5450- 5480 f eet ) .

Bef ore st i mul ati on resul t s were zer o MCFG/ day f or

bot h zones and af t er st i mul at i on r esul t s were 40 MCFG/ day and 107 MCFG/ day

'

respecti vel y.

The absence of " cool i ng ki cks" t hrough these two zones

. :

may be t he r esul t of t he borehol e not encount eri ng a f r actur e

4

system but t he f r acture system coul d be penetr ated and enl arged through

sti mul at i on.

Fract ur e dat a fr om cor e anal ysi s were not avai l abl e t o

determ ne i f f r actures were encount ered i n t he wel l i n t he t wo st i mul ated

zones.

Si bi l at i on Curves

As di scussed above, t he Si bi l ati on survey i s r un t o "l i st en" f or gas

bei ng l i berated i nt o t he borehol e.

Typi cal l y, the Si bi l at i on survey i s

r un i n conj unct i on wi t h the t emperat ur e sur vey.

I t shoul d be expected

t hat wi t h a "cool i ng ki ck" on t he t emperat ur e curve t here shoul d be a

corr espondi ng "noi se ki ck" on t he Si bi l ati on cur ve, t hus pr ovi di ng an

i

1

2

,

.

d

,

addi t i onal t ool f or l ocati ng gas accumul ati on and f r acture syst ems.

Si x of t he seven study wel l s had Si bi l at i on curves avai l abl e f or

anal ysi s.

A t ypi cal exampl e of t he Si bi l ati on/ t emperature r esponse t o

gas l i berati on i nt o t he borehol e i s shown i n Fi gur e 5. Thi s exampl e

was t aken f r om Wel l #20402 and i ncl udes t he i nt erval f r om 3340 t o 3420 f eet .

The l aboratory anal ysi s of t he core fr om thi s i nterval i ndi cates off gassi ng

of appr oxi matel y 1. 2 cu. f t . gas/ cu. f t . shal e and or gani c car bon cont ent

i r qngi ng f r om appr oxi matel y 3. 5 t o 4. 8 percent . Exam nati on of t he core

i ndi cates open f r actures t hr ough t hi s i nt erval . These f r actures may have

been i nduced dur i ng t he cori ng operati ons. Bef or e st i mul ati on t est data .

was zero MCFG/ day and af t er st i mul at i on dat a was 112 MCFG/ day. I n Wel l

D/ K#3, several zones were i dent i f i ed as pot ent i al l y gas pr oduct i ve based

on "noi se ki cks" i n t he Si bi l ati on cur ve but t he cor respondi ng "cool i ng ki ck"

11


15/36

,F . . __-- ; . . -a .

1_a..

_- _. _.

_

;

^

1

- ,

i

GAMMA RAY

SISILATION

TEMPERATURE

Q

I NCREASI NG

DEPTH

+-Sibilation

Temperaturb-

Normal Tern p.

Gradient 7

' 3490

Fi gur e 4. Wel l #20337 showi ng an exampl e of t emper at ure

curve def l ecti on ( "cool i ng ef f ect" ) wi th

possi bl e Si bi l ati on curve ki ck t hr ough a

zone whi ch t ested 133 MCFG/ day af t er st i mul at i on.

12


16/36

C.

1.. . .

.;

ig?.

GAMMA RAY

[ API UNI TS1

I NCREASI NG

L7

DEPTH

3340

3350

3360

3410

3 420

SIBiLATION

TEMPERATURE

openFI l eNo. 144

I NCREASI NG

I NCREASI NG

*

Temperature

I

Normal Temp.

Gradhnt /

Normal Temp.

Fi gur e 5.

Wel l #20402 showi ng an exampl e of Si bi l at i on

and t emper at ure cur ve r esponse t o gas

ent eri ng t he borehol e.

13


17/36

.

\

-.

OpenFi l eNo. 144

I

.

i .

on t he t emperat ur e curve was not apparent ( Fi gur e 6). Al so, i n Wel l D/ K#3,

I

I

a very

good

"cool i ng ki ck" was apparent t hr ough a zone f r om 2730 t o

: , : .

2820 f eet

but

on t he Si bi l ati on curve there was onl y a margi nal or no.

_ _ . .

:

appar ent r esponse t hr ough t he zone (Fi gure 7) . Thi s pr obl em

was

al so

.

> L

:

f ound i n Wel l #20337 t hrough t he zone 3526 t o 3574 f eet . I t shoul d be not ed

. , ' II I 1 t hat i n Wel l 820337, t he zone 3526 t o 3574 f eet was st i mul ated and af t er

s4

- v'

- 1

st i mul at i on resul t s show a 133 MCFG/ day gas potent i al . Corr espondi ng

?

Si bi l ati on and t emperat ur e ki cks on t he l ogs are cer t ai nl y good evi dence

.

f or gas accumul at i on and f r act ures but zones where ei t her one of t he two

. . i

4

cur ves do not r espond st i l l warr ant f ur t her eval uati on.

Resi st i vi t y Cur ve Over l ays

- _

The pur pose of t hi s t echni que i s t o i dent i f y zones of i ncr eased

por osi t y ( f r actures) as i ndi cated by separati on of a shal l ow i nvest i gati on

resi sti vi ty curve f rom a deep i nvesti gati on r esi sti vi ty curve or curves.

i

Thr ee of t he seven st udy wel l s have t he appr opr i ate l ogs avai l abl e f or

t hi s. anal ysi s ( #20402, D/ K#3, and 20401). Wel l #20402 was t he onl y wel l

where separati on of t he r esi st i vi t y cur ves was apparent . I n t hi s wel l ,

t hese zones are l ocated at 3370 t o 3381 f eet and 3392 to 3400 f eet

( Fi gur e 8) . These zones were al so charact eri zed by Si bi l ati on and

t emperatur e ki cks.

Exam nati on of t he core i ndi cates open f r actur es t hr ough

t he t wo zones.

Of f gassi ng val ues of 1. 2 cu. f t . gas/ cu. f t . shal e and

r el ati vel y hi gh organi c carbon cont ent r ange f r om 3. 5 t o 4. 8 percent were

deter m ned f or t he t wo zones.

Bef or e st i mul ati on testi ng i ndi cated zero

jI

MCFG/ day and af t er st i mul at i on 112 MCFG/ day.

Exam nati on of t he D/ K#3 wel l cor e I ndi cates sever al zones of f r acturi ng,

yet t he r esi st i vi t y curves show no apparent separat i on.

Based on t he l i m t ed number of wel l s avai l abl e f or t he r esi st i vi t y

t ool overl ay anal ysi s,

i t appears t hat thi s t echni que gi ves very l i m t ed

i ndi cati ons f or the l ocati on of f ractures.

Addi t i onal wel l s wi t h the

appr opr i ate r esi st i vi t y l ogs and cores ar e needed f or a more concl usi ve

anal ysi s of t hi s techni que.

Pr oduct i on I ndex

Pr oduct i on I ndi ces were cal cul ated or pr evi ousl y comput er generat ed

f or al l seven study wel l s.

The f ut ur e val ue of usi ng Pr oduct i on I ndi ces

as a r el ati ve i ndi cator of potent i al gas pr oduct i on wi l l r equi r e many more

14


18/36

Open File No. 144

GAMMA RAY

I

[API UNITS1

INCREASING

: I

DEPTH

3220

3230

3240

3250

3260

3270

3280

3290

SIBILATION TEMPERATURE

INCREASING,

INCREASING .

l

t-Temperature

Fi gure 6.

Wel l D/ K#3 showi ng Si bi l at i on cur ve r esponse and

no cor r espondi ng t emper ature curve r esponse to

gas possi bl y ent eri ng the bor ehol e.

15

.

__ __ _. .___ .


19/36

Open File No. 144

GAMMA RAY

[API UNITS]

INCREASING

I

1979 devonian shale.pdf

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