H Y D R O T H E R M A L P R O D U C T S F O R M E D F R O M M O N T M O R I L L O N I T E C L A Y S Y S T E M S 1

by

STANLEY B. ~r 2

Sun Oil Company, Richardson, Texas

A B S T R A C T

An investigation of the behavior of clay systems in drilling fluids was begun in 1958 to determine the cause of gelation in lime-treated muds with increased temperatures incurred during drilling operations. Mud systems were evaluated by physical property measurements, cation exchange data, X-ray diffraction analysis, and electron microscopy before and after hydrothermal treatment. Selected samples were rerun after two years' storage at laboratory temperatures.

High-temperature gelation of lime-caustic muds is caused by the synthesis of calcium silicate hydrates, hereafter referred to as CSH, in general and tobermorite (XCaO, Si02, H20 } specifically. These materials are considered the principal cementing agents of Portland cement. Spheroidal poorly crystallized tobermorite was produced from interlayered illite- montmorillonite muds. Laths and needles of crystalline tobermorite (11.3-11.6 ~ type) were synthesized from the pure montmorillonite systems. Zeolite minerals were synthesized concurrently and were the dominant alteration product when Ca(OH)2 was not added to the system.

Synthesized aged (2 years) mud systems were studied after 8 weeks of dialysis with dis- tilled water. Corundum was observed in samples where tobermorite formed, and was the domi- nant insoluble residue after HC1 treatment, l~Iueh sharper diffraction maxima were obtained of the CSH compounds after dia]ysis or glycerine washing.

"Al-ehlorite," "Al-vermiculite," and "Al-micas" were synthesized when treatments in- cluded aluminum ions. The products formed were of varying stabilities after washing with distilled water and HC1. Glycerol expanded the montmorillonite which had not reacted, but no expansion from the 10 -~ or 14/~ d(001) spacing of the new product oceurrred.

I N T R O D U C T I O N

T h e so l id i f ica t ion o r ge l a t i on of l i m e - t r e a t e d d r i l l i ng m u d s is a p r o b l e m in

t h e d e e p e r bo reho le s in t h e Gulf Coas t a r e a w h e n t e m p e r a t u r e s e x c e e d

121 ~ These l i m e muds , in w h i c h b e n t o n i t e ( m o n t m o r i l l o n i t e ) is t h e bas ic

ing red ien t , were t r e a t e d w i t h caust ic , l ime, a n d o rgan i c t h i n n e r s to p roduce

t h e phys i ca l p rope r t i e s cons i s t en t w i t h d e p t h , t y p e of f o r m a t i o n , a n d o t h e r

fac tors . E x c e l l e n t r ev i ews of t h e c h e m i c a l t r e a t m e n t of d r i l l i ng f luids

1 Published by permission of Sun Oil Company. Sun Oil Company, Production Research Laboratory.

276

HYDROTHERM.AL PRODUCTS FORMED 277

(Chaney, Oxford and Chisholm, 1942) and of the use of clay in drilling fluids (Larsen, 1955) are available. Early studies of the problem (Gray, Neznayko and Gilkeson, 1952) concluded that the observed thickening process was not due to gelation of the type commonly found in bentonite- water systems. It was also concluded that pressure was not a major factor in high-temperature gelation of lime muds. Laboratory studies were begun by many investigators to interpret the mechanism involved in the hardening or solidification process observed in the lime-treated muds at high tempera- tures. A preliminary study was initiated in 1956 by Sun Oil Company. The X-ray diffraction work reported here was begun in 1958 and involved the samples prepared in the initial study and those subsequently prepared.

Hydrothermally treated simple-system muds were selected for investi- gation because of the complexity of field muds with added formational material, weighting material, and lost circulation material. Previous work by R. E. Grim and W. F. Bradley for the Baroid Sales Division (Gray, Neznayko, and Gilkeson, 1952) indicated the synthesis of analeime and some poorly crystalline hydrated calcium silicate from bentonite slurries and geological formations. The CSH compound formed was tentatively identified as xonotlite by Bradley.

The hydrothermal and analytical work on the "mild treatments" was done at the Sun Oil Company Production Laboratory at Beaumont, Texas, under the direction of B. G. Chesser. His help in the preparation and characterization of the mud systems has been invaluable and his aid is gratefully acknowledged. The electron micrographs were made by L. G. Bostwick of the Sun Oil Company Marcus Hook R. & D. Laboratories and his assistance is also acknowledged.

E X P E R I M E N T A L M A T E R I A L S AND M E T H O D S

The centrifuged Wyoming bentonite used in most of the reported experi- ments was furnished by the Baroid Sales Division of the National Lead Company and was a montmorillonite of high purity. The illite clay was obtained from the Illinois Clay Products Company and was an inter- layered illite-montmorillonite. API Project no.49 clay minerals were obtained from Ward's Natural Science Establishment, and included API no. 34 hectorite (Hector, California) API no. 11 montmorillonite (Santa Rita, New Mexico); API no. 27 bentonite (Belie Fourchc, South Dakota); and API no. 41 metabentonite (Tazeweil, Virginia).

Homoionic clays of the centrifuged bentonite and illite were made for starting materials in the 1956 series. The calcium, barium, and magnesium clays were made by washing with 1 N salt solutions, filtration, resuspension, and washing through four cycles. The sodium clay was made using exchange- resin techniques employing several runs with fresh Na-resins. Exchange

278 NINTH NATIONAL CONFERENCE ON CLAYS AND CLAY MINERALS

and X-ray diffraction da ta are given for these mater ia ls in Tables 1 and 2. API s tandard clay minerals were purified by centr i fugat ion-dispersion techniques and were sodium saturated. All repeated exper iments in 1958 were duplicates of the 1956 series.

TABLE 1.--EXChAnGE DATA AND pH VALUES FOR STARTING I~IOMOIO~-IC CLAY SYSTEMS

Clay Treatment C.E.C. Meq of pit (meq/100 g) Cation

Na-bentonite 1 Ca-bentonite Mg-bentonite Ba -bentonite Na-illite ~ Ca-illite Mg-illite Ba-illite

89.8 88.2 91.0 85.3 23.9 19.8 21.4 20.1

108.0 90.9 94.5 93.8 22.2 16.9 14.9 16.4

9.0 8.6 8.5 8.4 8.6 7.1 7.0 6.6

1 Original bentonite: C.E.C. 90.9, Na 82.5, Ca 32.4, Mg 14.8 meq. 2 Original illite: C.E.C. 21.7, Na 1.7, Ca 13.9, Mg 13.2 meq.

TABLE 2.--DIFFRACTION DATA FOR HOMOIONIC STARTING CLAYS

Bentonite Illite

Treatment Na Ca Mg A1 Na (A) (A) (A) (A) (A)

Oriented Slide Glycerol

550 ~

Kembreak

12.6-11.8 18

9.9

14.9

15.7 15 .4-14 .9 18.0-17.7 18 18 18

10 l0 9.9

10.8-10.3 18 10 10.1 ll.1

Methods

Exchange data.-Cation exchange capacities were de termined by succes- sive shakings with increments of 1 N a m m o n i u m acetate followed by Solox washing (Graham and Sull ivan, 1938, p. 176) and de terminat ions of nitro- gen by Kje ldahl disti l lation. Exchangeable cations were de termined from the decantate by s tandard gravimetr ic and photometr ic procedures.

X-ray di/[raction.--Random powder moun t s and oriented films of dis- persed clay or slurries were run for all samples before and after hydro- thermal t r ea tmen t and after washing each with distil led water to remove

HYDROTHERMALPRODUCTS FORMED 279

excess salts. X-ray diffraction patterns were made using a Philips dif- fractometer with nickel filtered copper radiation. Special treatments (gly- cerol solvation, differential heat, cation saturation treatments, dialysis) were used as required for identification of clays and acid-soluble ma- terials. Concentration and purification of samples were accomplished b y glycerol washing, dialysis, acid solubility, water washing, and centri- fugation.

Hydrothermal procedure.--Treatment chemicals were added as solids to the various clay suspensions and stirred with a Hamilton-Beach mixer. The samples were aged overnight and restirred. One-half of the stirred sample was removed for room-temperature storage and the remaining one-half was used for hydrothermal treatment. Treated muds were heated for 168 hr at 176 ~ (350 ~ in Baroid steel bombs. At this temperature the water vapor pressure would be approximately 135 psi. The bombs were cooled to room temperature and physical measurements (not reported here) were recorded on the undisturbed mud. Aliquots were removed from both halves of the original sample and stored in polyethylene bottles for X-ray diffraction and electron micrographic studies.

E X P E R I M E N T A L R E S U L T S

The exchange and p i t data for the clay minerals used in these studies are summarized in Table 1. Variations in exchangeable cations and ex- change capacities are within the range normally observed for the methods used. The p i t by clay species and saturating cation is in accord with expected behavior.

Table 2 gives the d(001) spacings of the Wyoming bentonite and the illite with various cation saturations and preparations. Variations in the spacings are due to hydration effects for bentonite and to interlayering effects for the illite (mixed-layered lattice with montmorillonite). The standard procedure was to prepare oriented clay films on glass slides which were dried for 48 hr over CaC12 prior to scanning the 14 ~ to 2 ~ angle (2 0). The data in Tables 1 and 2 are given for comparison with the results of hydrothermal treatment reported in the next sections.

Illite Systems

Very little change was observed in the interlayered illite-montmorillonite system when treated with hydroxides of sodium, potassium, calcium, and aluminum prepared as shown in Table 3. A 27.34 percent Na-illite sdspension was used to give viscosities and exchange concentrations com- parable with the montmorillonite systems. The room-temperature treat- ments showed no exchange except for gibbsite (A1203 �9 3H20 ) produced in

280 NINTH NATIONAL CONFERENCE ON CLAYS AND CLAY MINERALS

the a luminum t rea tment and some calcite product ion in the caust ic- l ime-Kembreak 1 t reatment . Hydro the rma l reaction produced slight changes in all systems except the one t rea ted with N a O H ; nephelite ( 3 N a ~ 0 - K 2 0 . 4 A 1 2 0 s. 9Si02) in the K 0 H t rea tment ; traces of tober- morite with Ca(0H)2 with decreased in tensi ty of the d(001) of mont- morillonite; and conversion of the gibbsite to boehmite (AI~O a �9 H20 ) in the a luminum treatment .

TABLE 3.--ILLITE TREATMENTS BEFORE AND At~ER HYDROTHERMAL REACTIOI~

Treatment1 At Room Hydrothermal Reaction Temperature

10.23 g NaOH 16.23 g K0K 9.26 g Ca(OH)2 6.5 g A|(OH)3

1.0 g NaOI-I 9.26 g Ca(OH)2 3 g Kembreak

No change No change No change No change Gibbsite

No change Calcite

No change Nephelite Tobermorite (tr) Calcite No change Boehmite

Tobermorite (11.3 t~) Loss 14/~ d(001) 10 ~ Illite

1 Starting material 350 ml 27.34 percent Na-illite suspension.

Tobermori te was formed in much greater concentrat ions in the l ime- caus t ic -Kembreak illite system than in any of the single hydroxide treat- ments. Plate 1 B shows the morphology of the poorly crystallized tober- morite as compared to the room temperature sample in Plate 1A. The 14 • d(001) and the 10.3-10.8 A spacing of the room-tempera ture diffracto- gram are not present in the hydro thermal ly reacted sample, thus indicating almost complete destruction of the montmori l loni te component of the mixed-layer structure. The 11.3/~ tobermori te spacing was somewhat broadened and was removed by HC1 t r ea tmen t leaving a sharp 10/~ d (001) reflection. Similar behavior was observed for all t rea tments t ha t included Ca(OH)~-illite systems. The powder pat terns obtained on material f rom hydrothermal ly reacted i l l i te-montmoril lonite-Ca(OH)2 are identical t6 published tobermori te data (Heller and Taylor, 1956, p. 36).

1 Kembreak--a calcium lignosulfonate recovered from waste sulfite liquor obtained from the pulping of coniferous trees (I~I.W. 1000-20,000). Each monomer of the polymer is con- sidered to have 5 benzene rings with C 3 side chains, 1 methoxy group, 1/5-1/2 sulfonie acid group, and 1/6--1/3 phenol group.

PLATE 1.--Electron micrographs of room temperature illite (A) and illite treated hydrothermally with lime-caustic (B).

HYDROTHER~IAL PRODUCTS FORMED 281

Wyoming Bentonite Systems

T h e 1956 b e n t o n i t e t r e a t m e n t s , a f t e r t w o y e a r s of ag ing , a re g i v e n i n

T a b l e 4. Al l t r e a t m e n t s we re d o n e o n 350 m l of a 5 p e r c e n t b e n t o n i t e s u s p e n -

s ion w i t h s a l t s as i n d i c a t e d i n t h e t a b l e a n d d i s c u s s e d be low.

TABLE 4.--BENTONITE TREAT~EI~TS (AGED) BEFORE AI~D AFTER HYDROTHER/s REACTION

At Room Treatment1 Temperature Hydrothermal Reaction

10.23 g NaOH

16.23 g KOK

9.26 g Ca(OH) 2

40.68 g Ba(OH)~

7.29 g ~r 2

6.5 g AI(OH)a

25.42 g MgCI~

1 g NaOH 4.63 g Ca(OH)~

4.63 g Ca(OH)2 3.64 g Mg(OH)~

1 g NaOH 9.26 g Ca(OH)2 3 g Quebracho S

1 g NaOH 9.26 g Ca(OH) 2 3 g Kembreak

Analcime (tr) Na~CO a

Phillipsite

Calcite

BaCO 3 Brucite

Vermiculite-Chlorite

Gibbsite

No change

Portlandite Calcite Gibbsite Tobermorite (tr)

No change

Tobermorite (tr)

Tobermorite (tr) Gibbsite Gyrolite Truscottite

Analcime MontmoriUonite (15 percent)

Mixed layer (11.1 and 10.0) Phillipsite Corundum

Tobermorite Calcite Osannite (?)

Ba-zeolite?

Mg-vermiculite

Saponite?

Gibbsite

Corundum

Mont. Al-mica

No change Corundum

Tobermorite Thompsonite Analcime Xonotlite

Montmorillonlte Vermiculite Tobermorite

Tobermorite Analcime Calcite Ettringite Montmorillonite (tr)

Tobermorlte Analcime Corundum Calcite 4 CaO. Al~O a �9 x H~O

1 Starting material was 350 ml of 5 percent Na-bentonite suspension. ~r morillonite not shown except where a change in concentration noted.

cc.~ 19

282 NINTH I~ATIONAL CONFERENCE ON CLAYS AND CLAY MINERALS

NaOH.-The room-temperature sample contained sodium carbonate and a trace of analcime (NaAISi~Oe �9 H~O) in addition to the original montmoril- lonite. After heating, approximately 85 percent of the montmorillonite was converted to analcime.

KOH.--At room temperature a small amount of phillipsite [(Ca, K2)A12Si4012.4.5H20 ] was formed, and the sample remained prin- cipally montmorillonite. Hydrothermal reaction produced a mixed-layer montmorillonite-illite (11.1 • and 10.0 J~), phillipsite, and corundum (A12Oa).

Ca(OH)2.-At room temperature, portlandite [Ca(OH)2], calcite, and Ca-montmorillonite were formed. After hydrothermal treatment there remained a 15.7 J~ and a 12.8 A montmorillonite, tobermorite, calcite and probably some ossanite (Na-amphibole).

Ba(OH)~.--The barium ion adsorption and coating gave the appearance of an amorphous material both before and after heating. Washed samples showed the presence of BaCO a and Ba-montmorillonite in the room-tem- perature sample. An unknown mineral, probably a barium zeolite, was formed hydrothermally.

Mg(OH)~.-At room temperature the principal products were Mg-mont- morillonite and brucite [Mg(0H)~] along with small amounts of a vermi- culite-chloritelike mineral. A~ter hydrothermal treatment the dominant mineral was still montmorillonite with some Mg-vermiculite. Saponite probably formed in small amounts, but its presence could not be definitely substantiated.

Al(OH)a.-Gibbsite and a 12.9~ montmorillonite developed during room-temperature storage. Hydrothermal treatment produced gibbsite, corundum, interlayered montmorillonite-"Al-mica" and unreacted mont- morillonite. There was some evidence that even at room temperature some interlayered material was produced. Powder patterns gave diffuse peaks at 11.2, 11.7, and 13.6 A, all of which sharpened to 12.0-12.6 J~ after HC1 digestion.

MgCl~. - N o change was observed except the formation of some corundum which indicates minor hydrothermal destruction of montmorillonite.

NaOH-Ca(OH)~. - Calcite, gibbsite, portlandite, Ca-montmorillonite and a trace of tobcrmorite were formed under room-temperature con- ditions. Hydrothermal reactions produced tobermorite, thompsonite (NaaCagAl~lSil~Os0.24H20), analcime, and xonotlite [Ca6Si6OI~(OH)2 ] while about 50 percent unreacted montmorillonite remained.

Ca(OH)~-Mg(OH)~.-No change was observed in the unheated material. After hydrothcrmal treatment, a 12.9/~ montmorillonite, a 14.7 A vermi- culite, and a 11.7 ~ tobermorite were observed. Glycerol solvation gave an 18/~ montmorillonite and a 14.7.4 vermiculite, both of which collapsed to 10 A with 500 ~ heat treatment. The tobermorite was dissolved b y HC1 and dehydrated to the 9 A tobermorite with heat.

HYDI~OTHEI~M~J~ PRODUCTS FOI~MED 283

NaOH-Ca(OH)~-Quebrachol.-There was no change after storage a t room temperature except for minor production of tobermorite. Hydro- thermal t reatment destroyed almost all the montmorillonite and formed tobermorite, analcime, calcite, and ettringit~ (6CaO �9 Al~O a �9 3S0 a �9 3H20 ).

NaOH-Ca(OH)~-Kembrea]c.-Traces of tobermoritc, gibbsite, gyrolitc (2CaO �9 3SiO 2. 2H20), and truscotti te (CaO. 2SiO 2. 1/2H~O) were formed in the room-temperature storage sample. Tobermorite, analcime, corundum, calcite, and calcium aluminate (4CaO. A120 a �9 xH~O) were formed hydrothermally.

Table 5 gives selected data for 5-percent montmorillonite suspensions immediately after t rea tment was completed. Two samples with iron sub- stituted for aluminum, and one with magnesium substituted for calcium are also included. In general, the higher the calcium hydroxide concen- tration the more completely the montmorillonite was destroyed, with subsequent formation of new products.

In the room-temperature experiments traces of tobermorite were formed at the highest [9.26 g Ca(OH)s ] calcium concentrations and traces of wairaikite (CaO. Al~O a �9 4SiO~) at the lowest (2.5 g) calcium hydroxide concentrations. Portlandite and calcite were also produced. The hydro- thermal experiments in this series show a stepwise effect with the amount of calcium hydroxide present on the degree of conversion of montmoril- lonite to tobermorite, thompsonite, and analcime. The data are listed in order of the amount present.

Montmorillonite systems treated with decreasing concentrations of cal- cium and aluminum are also given in Table 5. In the room-temperature controls no change is apparent. The hydrothermally t reated samples show quite different products as a function of changing concentrations of calcium hydroxide. Tobermorite occurs only as traces in the fresh material, whereas it is the dominant mineral in the aged material. Foshagite (5 CaO. 3 Si02.3 H20), thaumasite (CaSO 4 �9 CaCO a �9 CaSiO a 14H20), thompsonite, ettrin- gite, gibbsite, calcite and traces of tobermorite are present at the highest calcium hydroxide concentrations with almost no residual montmorillonite. Decreasing the calcium content by almost one-half leaves about one-half or more of the montmorillonite unreacted and causes the formation of an "Al-chlorite-Al-vermiculite" compound with tobermorite and thaumasite. With the lowest Ca-A1 concentrations a trace of tobermorite is formed at room temperature; and analcime, gibbsite, montmorillonite, and tober- morite are observed in tha t order in the hydrothermally treated sample. Acid t reatment of the hydrothermal end products show gibbsite, mont- morillonite, and colloidal silica as the acid-insohible residue.

1 Quebracho-a hot water extract of the Quebracho tree (60-70 percent tannin). 19"

284 NINT~ NATIONAL CONFERENCE O1~ CLAYS AND CLAY MINERALS

TABLE 5.--BENTONITE SYSTEMS IMMEDIATELY AFTER HYDROTHERMAL TREATMENT

Treatment1 At Room Temperature Hydrothermal Reaction

1 g NaOH + 3 g Kembreak

9.26 g Ca(OH)2

5.0 g Ca(OH)2

2.5 g Ca(OHh

Calcite Tobermorite (tr)

Por tlandite

Calcite Portlandite Wairakite (tr)

I g NaOH + 3 g Kembreak + 6.5 g Al(OH)a 9.26 g Ca(0H)2 Gibbsite

Portlandito Calcite

5.0 g Ca(0H)2 Gibbsite

1 g Na0H -t- 2.5 g Ca(OH)2 Gibbsite 3 g Kembreak + 1.76 g 33(0H)3 Tobermorite (tr)

1 g NaOH, 3 g Kerabreak + 5.0 g Ca(OH)2 11.12 g A1CI a 33-mont. (18 J~)

33-mica (10.1/~) A1C1 S NaCI

13.1 g F%0 a Hematite Fe-vermieulite

Halite 13.54 g FeC13 �9 6H~O

No change 1 g Na0H + 3 g Kembreak 7.29 g Mg(OH)2

Tobermorite Analcime Thompsonite Ca.lcite (tr), Mont. (tr) Tobermorite Analcime Montmorillonite Thaumasite (?) Montmorillonite Analcime Tobermorite Calcite

•oshagite Thaumasite Thompsonite Ettringite Calcite Tobermorite (tr) Gibbsite (tr) Montmorillonite Al-ehlorite-Al-vermiculite Tobermorite Thaumasite Analcime Gibbsite Montmorillonite Tobermorite

Al-chlorite (14.2, 7.11, 3.54A) Gibbsite NaC1 Gypsum Hematite Analcime Tobermorite Pyrophyll~te ? Montmorillonite Halite Goethite

Montmorillonite-Vermiculite Montmorillonite

1 Starting material was 350 ml of 5 percent Wyoming bentonite to which additives tested below were made as dry powders.

HYDROTHERMALPRODUCTS FORMED 285

When A1C13 was substituted for AI(OH)s to give an acid medium, A1- montmorillonite (18 •) and "M-mica" (10.1 J~) were produced at room temperature and "Al-chlorite" (1412, 7.11, and 3.54 :~) hydrothermally. The chlorite spacings are retained after heating to 550 ~ but they are destroyed by 10 percent HC1 digestion.

Substitution of Fe203 (hematite) for AI(OH)s in the system produced unreaeted montmorillonite, hematite, and "Fe-vermiculite" (14.2-14.7 J~ for glyeerol-solvated sample; 9.6 A when heated to 500 ~ Hydrothermal treatment formed analcime, tobermorite and pyrophyllite (?) and retained residual hematite and montmorillonite. When FeC13 �9 6H20 was sub- stituted for the oxide, no change was observed other than some production of goethite hydrothermally.

The substitution of Mg(OH), for Ca(0H)2 produced no change at room temperature and formed a random interlayered montmorillonite-vermi- culite clay hydrothcrmally.

A P I Project no. 49 Clay Minerals

Standard clays were submitted to the same treatment as the lime- caustic-Kembreak bentonite systems to determine the changes with different lattice charges and ionic substitutions.

A P I no. 34 hectorite. --The room temperature samples showed no change, but the hydrothermal treatment developed 10.3., 9.8, and 9.4 A d(001) spacings with some calcite and hydromagnesite (SMgO. 4C0~. 5H20 ) production. Heat collapsed the lattice to 9.8 ~ and HCl-treated material gave only a colloidal silica type pattern.

A P I n o . l l montmori l loni te . - -No changes were observed in the room- temperature treatment. The hydrothermal treatment caused the synthesis of tobermorite, but some montmorillonite was unreacted. Some mont- morillonite-illite interlayering was observed in the original sample and was retained in the acid-treated and glycerol-treated slides.

A P I no. 27 ben ton i t e . -No change was apparent from the room-tempera- ture treatment of this sample. The hydrothermally treated sample was almost completely converted to tobermorite. Heat treatments of the reacted material indicated that some montmorillonite-tobermorite mixed layer lattice mineral had been formed. The glycerol-treated oriented slide gave only a 11.6 A spacing. A small amount of analcime was formed during the hydrothermal reaction.

A P I no. 41 me taben ton i t e . -The original Tazewell sample had a dominant 10.6 J~ d(001) spacing and showed traces of kaolinite. The room-tempera- ture treatment gave a sharp 10.5 A peak with an 11.2 A shoulder and an 11.7/~ shoulder. Heat and glycerol solvation confirmed the mixed-layer type of crystallization and indicated no change from the original material. After hydrothermal treatment the mineral aggregate was illite, mont-

286 NINTH I~ATIOIqAL CONFERENCE ON CLAYS AND CLAY MINERALS

morilionite, and mixed-layer clay. Acid digestion resulted in a colloidal silica-type pattern indicating much change during hydrothermal treatment. I t is suggested that a scawtite (4 CaO. 3 C02 .3 SiO~)-tobermorite type of intergrowth is present here, but so poorly crystallized as to be unidenti- fiable specifically.

Dialyzed Aged Hydrothermal Mud

Samples of the l ime-caustie-Kembreak types of mud, which approximate the types of drilling mud actually used, were purified by dialysis for 8 weeks to determine the identity of the CSH compounds and the distribution of ions after dialysis. The data obtained in the internal and external solutions at the completion of the dialysis through a cellulose membrane are recorded in Table 6. The external solution was distilled-water changed weekly. The

TABLE 6.--CHEMICAL ANALYSES OF DIALYSIS COMPONENTS

OF AGED HYDROTHERMAL LIME--CAUSTIC--KEMBREAK-- BENTONITE SYSTEM

External Internal Constituent Solution Solution

(mg/100 ml) (mg/100 ml)

A1 Fe Ca Mg S04 SiO~ Na

7.2 0

296.0 3.2

45.2 31.5 62.0

0 0 tr tr

16.8 0 2.8

internal solution was obtained by washing and centrifugation at the end of the dialysis period. Only small quantities of sulfate (from the Kern- break) and sodium were present in the internal solution. The external solu- tion was dark brown from the organic thinner (Kembreak).

X-ray diffraction analyses of two size fractions of the suspended material, 2-0.2 g and less than 0.2 ~t, gave excellent oriented patterns for tobermorite. The d(001) spacing of 11.6 • is due to the incomplete AI replacement by Ca ion in "oetahcdral" coordination (Kalousek, 1957). The solid material at the bottom of the membrane bag contained tobermorite as the dominant mineral, and smaller amounts of hillebrandite (2CaO �9 Si02. H,O), thomp- sonite, analcime, and residual montmorillonite. Glycerol solvation produced a low intensity 18 A d(001) and a very strong 11.6 A peak; acid treatment (l N HC1) produced a colloidal silica-type pattern with incipient ~-tri- dymite peaks, corundum, and a weak montmorillonite pattern. There was some indication of traces of foshagite, gyrollte, and truscottite. Repetition

I~YDROTHERMAL PRODUCTS FORMED 287

of these experiments with newly made hydrothermally reacted material produced analeime, tobermorite, and unreaeted montmorillonite. Increased background of the X-ray patterns before dialysis and increases an alu- minum in the external solution are indicative of the amorphous aluminum compounds without aging.

Summary o/Experimental Results

Figs. 1 and 2 summarize the results of experiments before and after hydrothermal treatments. The original ionic concentrations of Al, Ca, and

IO0%AL + + +

DCo-Silicale Hydrate / ~

oSulfote /

/~Tho . . . . ire /

~7 Sillirn anite / ,~'~. ] \ Numbers indicate ,/-,~.."~ .~.,.." ~ A n a I o ~' e )k

IO0%No+/ [ po% ~, tx~ , / ~ 2' ~100 I ondl5

%Co ++

FIGUI~E 1.--Bentonite clay treatments (Table 7) after room temperature storage.

Na used in the various concentration ranges are computed in Table 7. All aluminum compounds were assumed to be completely soluble, even though the AI(OH)a is insoluble at room temperature. Ions structurally bonded in the montmorillonite were not considered in the original ionic concentrations. All additions were calculated from analyses and the values are summations exclusive of concentration of bonded lattice ions in the clay. The AI ion concentration ranged from 0-488 meq; the Ca from 70-253 meq, and the Na ion from 40-207 meq. These figures are based on the amount present in the original 350 ml of the 5 percent bentonite suspension.

Fig. 1 was constructed to show by sample numbers (Table 7) the location of each sample relative to the percentage composition of the _A_I, Ca, and Na ions. Mineral synthesis of the unheated sampIes is superimposed upon

288 N I N T H NATIONAL CONFERENCE ON CLAYS AND CLAY ~IINERALS

Sample locat ions

c]

• Gibbsite far AL§ /

OCSH formation in /

I 00 % Na +:

I 0 0 % AL +++

2 \

J"~ 3 "

I 0 0 % Ca ++

FIGURE 2 . - -Bentoni te clay t r ea tmen t s (Table 7) after hydro the rmal reaction.

TABLE 7.--Na, Ca, A1 IoNic COI~CEI~TRATIONS IN MILLIEQUIVALENTS AND AS PERCEI~TAGES O1~ TOTALIONIC COI~CENTRATIO/~ OF Na + AI + Ca FOR 15 ~[UD TREATMENTS

Sample Sodium (Na) Calcium (Ca) A luminum (AI) Number (percent) (meq) (percent) (meq) (percent (meq)

1 2 3 4 5 6 7 g

9 10 I I 12 13 14 151

Total meq

297.19 13.5 537.79 7.5 972.68 21.3 181.98 22.2 422.58 9.4 459.73 8.8 350.07 23.5 515.06 23.9 847.45 24.4 114.37 35.3 179.51 22.4 162.17 32.2 204.58 30.7 294.69 29.0 297.19 13.5

40.34 40.34

206.93 40.34 40.34 40.34 82.64

123.64 206.93

40.34 40.34 52.29 62.90 85.46 40.34

86.5 256.85 47,8 256.85 26.4 256.85 77.8 141.64 33.1 141.64 30.8 141.64 40.7 141.64 27.5 141.62 16.7 141.62 64.7 74.03 41.3 74.03 45,7 74.03 36.2 74.03 25.1 74.03 86.5 256.85

0 0 44.7 240.6 (i) 52.3 498.90

0 0 57.5 240.6 (i) 60.4 277.75 (s) 35.8 125.79 48.6 249,8 58.9 498.9

0 0 36.5 65.14 (i) 22.1 35.85 33.1 67.65 45.9 135.20

0 0

(i) Insoluble A1 as gibbsite. (s) Soluble as A1C13. z Same as no. 1 except 10 ml glycerine added.

HYDROTHERMALI:~ODUCTS FORMED 289

the triangular coordinates. Fig. 1 shows the following mineralogical effects from these ion treatments without heating:

(1) Montmorillonite remains the dominant mineral. (2) Portlandite generally remained as a major enti ty when the Ca ion

concentration exceeded 55 percent of the three ion summation. Sample 8 was an exception in having only a trace of portlandite.

(3) Gibbsite persisted when it was the source of added aluminum. (4) Traces of tobermorite and other CSIt minerals were formed in the

area of high Ca concentrations as in no.2 above. The presence of CStt compounds in sample 11 is rel/~ted to the concentration ratio of Ca to Na when the insolubility of the A1 source is considered. Some talc may have formed in sample 2, indicating some clay destruction but no CSI-I formation.

(5) All samples having soluble aluminum, and also sample 5, formed mixed-layered structures consisting of montmorHlonite with "Al-mica," "Al-chlorite," or "Al-vermiculite." These were present in small quantities.

Fig.2 gives the dominant minerals synthesized after hydrothermal treatment for 168 hr at 176 ~ (350 ~ The following summary statements can be made:

(1) Where Ca(OH)2 concentrations were 70 percent Ca ion or greater, and no free aluminum was added, tobermorite was the principal mineral formed, accompanied by large amounts of analcime/thompsonite and small quantities of other CSH forms. Complexes such as ettringite and thaumasite were formed where organic thinners were added. Montmorillonite remained in small amounts.

(2) At low meq concentrations of Na + Ca (114 meq), with no aluminum present, only a trace of tobermorite was formed (sample 10). As the alu- minum concentration was increased in the other samples, only traces of tobermorite were synthesized.

(3) Analcime (or thompsonite, or both) formed in large amounts in all samples except 6 and 9 which have 60.4 percent and 58.9 percent aluminum ion concentrations, respectively. These were the treatments using the highest concentrations of aluminum.

(4) Calcite formed in samples having greater than 50 percent calcium ion concentration.

(5) A sequence of montmorillonite mixed-layer clays with newly formed "Al-mica," "Al-vermiculite," and "Al-chlorite" occurs in all samples with free A1 ion added. At the highest Ca ion contents (25-50 percent) "Al-mica" is formed coincident with the lowest A1 concentration. In the intermediate range (15-25 percent Ca ion) "Al-vermiculite" is formed, and in the lowest range (less than 15 percent Ca ion) "Al-chlorite" is formed. Analcime was not formed in the A1C1 a treatment, emphasizing the role of hydroxyl in analcime formation.

290 NINTH NATIONAL CONFEI~ENCE ON CLAYS AND CLAY MINERALS

(6) Sample 9, with 59 percent A1 ion concentration, formed sillimanite (Al~Si05), gibbsite, and NaC1 as reaction products with no residual mont- morillonite remaining.

Electron Micrograph Study

A complete morphological study of each material used in this investi- gation was made with the electron microscope in 1956. All the micrographs were reinterpreted on the basis of X-ray diffraction studies and further information on the morphological characteristics of the CSH compounds. Plates 1 and 2 illustrate the different morphology of the two types of crystallization observed in this study. The spheroidal habit (Plate 1 B) was observed primarily in the hydrothermally reacted illite system. The ben- tonite-lime-caustic treatments (Plate 2A at room temperature and 2B after hydrothermal treatment), in which tobermorite was synthesized, produced lath- or needlelike crystals. These tobermorite micrographs are comparable to published electron micrographs of the two morphological types (Grudemo, 1955; Kalousek ~nd Prebus, 1958).

DISCUSSION

Tobermorite and related calcium silicate hydrates (CSH), zeolites, corun- dum, sillimanitc, "Al-mica," "Al-vermiculite," and "Al-chlorite" were products of hydrothermally treated drilling mud systems.

Tobermorite, reportedly rare in nature, occurs as fibrous materials and as platy crystals (Claringbull and Hey, 1952; Kalousek and Prcbus, 1958; Taylor, 1950; Megaw and Kelsey, 1956). Both morphologies have been artificially synthesized, the fibers at room temperature and the plates at temperatures up to 125 ~ (I-Ieller and Taylor, 1951; Kalousek and Prebus, 1958). The relatively large, perfect crystals from northern Ireland and the clearly amorphous material in Portland cement represent the extremes in crystallinity for tobermorite.

Ca. Si ratios can vary from 0.8 to 1.5 without apparent change in X-ray pattern or the appearance of a second phase (I-Ieller and Taylor, 1951, 1952). Four tobermorite hydrates are recognized (14 ~, 11/~, 10 A, and 9 A) and the 11.3 A form is the normal d(001) spacing; phase equilibria studies (Buckner, Roy and Roy, 1960) have shown that the 11.3/~ form is also the most stable. A d(001) spacing shift from 11.0 to 11.7 A occurred with the substitution of 3 percent aluminum in synthesized tobermorite, and small amounts of aluminum accelerated the transformation of the fibrous to the platy type (Kalousek, 1957). In Kalousek's experiments hydro- garnets formed when the aluminum concentration exceeded 5 percent.

Evidence presented here suggests that the tobermorite production from montmorillonite-type structures increases at a given concentration ratio

PLATE 2.--Electron micrographs of room temperature montmorillonite (A) and lime-caustic-montmorillonite treated hydrothermally (B).

HYDROTHERMALPRODUCTS FORMED 291

of NaOtt-Ca(OI~)2, as a function of the amount ofisomorphous substitution in the montmorillonite structure. For any one montmorillonite structure, the amount of tobermorite formed increases with increasing Ca(OH)2 when the NaOH concentration remains constant. In mixed-layer illite- montmorillonite structures, the montmorillonite is partially or completely converted to tobermorite leaving the free illite-miea as the residual.

In all the mi~ed-layer types studied, the spheroidal ["amorphous" type of Kalousek (Plate 1 B)] tobermorite was formed. This is in reality a poorly crystallized material with broad X-ray diffraction spacings. There is probably some interlayering with illite, but the general broadening prevents a clear-cut interpretation. X-ray diffraction patterns after aging are some- what better than those reported in the literature for the unaged spheroidal types. (The electron mierographs in Plate 1B were taken immediately after hydrothermal treatment and were not rerun after the aging process.) The morphological character of this type of material probably is asso- ciated with a difference in the rate of formation due to the more difficult accessibility of the reacting materials in interlayered structures.

The tobermoritc formed in the Wyoming bentonite and montmorillonite (API) systems in caustic-lime, or lime, environments was always fibrous, lathlike, or platelike crystals. The results reported here are consistent with published data for both crystal habits made from constituent gels (Kalousek and Prebus, 1958; Gard and Taylor, 1957).

The mechanism involved in the transformation of montmorillonite to tobermorite has not been specifically formulated. The amount of mont- morillonite destruction is related to the hydroxyl concentration, and the end products formed are governed by the cations present and their con- centration. The structural relationship of tobermorite to clay minerals (Taylor and I-Iowison, 1956) in general, and to vermiculite specifically (McConnell, 1955) have been published. Taylor (1950), Taylor and Howison (1956) and Megaw and Kelsey (1956) have discussed the possible structural transformations involved in this system. The dehydration mechanism in the various tobermorite hydrate forms has been discussed in detail (Taylor, 1959).

Clay mineral-CSH interlayering exists as a distinct possibility, parti- cularly with eosynthesis in calcareous montmorillonite alterations or alteration of mixed-layer clays in alkaline-lime systems. Some inter- layering is indicated by the nature of the basal d(001) diffraction peaks and values of submultiples in the mixed layer and montmoriUonite altered caustic-lime systems reported here. Acid digestion, glycerol washing, and dialysis confirm that the broadening in some patterns was because of random interlayering of tobermorite-illite or tobermorite-montmorillonite. Similar interlayered structures have been identified in at least two natural geological occurrences and in some soil profiles.

292 I~INTH NATIONAL CONFEI~ENCE ON CLAYS AND CLAY MINERALS

The almost universal appearance of zeolite minerals in the synthesized systems of tobermorite implies an association of these minerals in natural systems. Such is the case where they have been identified in sedimentary rocks.

The nature of the crystal structure of the CSI~ minerals and their asso- ciated d(00l) spacings are such as to overlap, coincide with, or exceed normal values of the principal clay mineral species. Since these systems occur in calcareous environments, normal acid dissolution techniques destroy the CSH minerals and gelatinize the associated zeolites. I t is thus not expected that the full extent of their natural occurrence can be realized until proper care is used to isolate these compounds. They are probably not as rare as they now are thought to be.

Similarly, the less common members of the zeolite group, particularly if interlayered with clay minerals, may also be overlooked in routine methods of analysis. Random interlayering of zeolites with clay minerals can occur and has been tentatively identified in a few sedimentary associations.

The formation of calcium silicate hydrates from clay systems in environ- ments of high ionic concentration has many implications in the genesis of clay minerals and associated geological materials. The low temperature of synthesis, room to 176 ~ places the probable occurrence of these minerals in almost any alkaline environment of deposition or alteration. The number of CSH species increases with aging and with changes in ionic concentrations, as do the associated end products. Most investigators have agreed that tobermorite is the first of the CSH compounds to form up to 125 ~ and that transformation to another phase occurs at higher temperatures of synthesis, or, as in the present case, with aging. The kind and amount of additional minerals formed would depend upon the phase equilibrium conditions of the system. Larger yields of CSH compounds were obtained from montmorillonite as the starting material than could be obtained under the same conditions starting with CaO-SiO~-H20 systems. The organic thinners used in some of these experiments appear to enhance the con- version of caustic-lime montmori]lonitc to tobermorite and may also be responsible for the slightly higher temperature formation range than that reported by Taylor.

The aging process was particularly important in the experimental con- version of gibbsite and amorphous aluminum compounds to corundum. The unaged systems contained either poorly crystallized gibbsite or amorphous aluminum material which could be removed with acid or other techniques. All aged systems, where octahedral aluminum had been released initially, synthesized corundum and it was the dominant mineral in the acid-insoluble residues.

Corundum synthesis was unexpected as the lowest comparable hydro- thermal synthesis temperature for corundum in the literature (~orey and

HYDROTHERMAL I:~ODUCTS FORMED 293

Ingerson, 1937, p.652) was 300 ~ a l though amorphous ma te r i a l was repor ted art 250 ~ I n general , mos t h y d r o t h e r m a l d a t a in the l i t e ra ture are for i m m e d i a t e l y observed phases and l i t t le work has been done to deter- mine the effect of aging on amorphous or subcrys ta l l ine ma te r i a l so charac- terist ic of the synthes ized end p roduc t s in this t y p e of experimer/ts . The da ta presented here suggest t h a t corundum is no t a lways as ind ica t ive of high t e m p e r a t u r e env i ronments as has p rev ious ly been thought .

Si l l imani te was formed in smal l quant i t i es f rom high a l u m i n u m - l i m e - caus t ic-nonaged sys tems a t 176 ~ bu t on ly in the one sys t em as no ted in Fig .2 . D a t a on synthes is t e m p e r a t u r e for s i l l imani te are ve ry genera l and more or less para l le l the co rundum s i tua t ion as g iven above.

Of pa r t i cu la r in te res t is the occurrence of " A l - m i c a , " "Al -vermicu l i t e , " and " A l - c h l o r i t e " wi th increas ing a luminum and decreasing calcium con- cent ra t ions in these h y d r o t h e r m a l sys tems. An increas ing number of "noncharac te r i s t i c" c lay minera ls are being r epo r t ed i n the l i t e ra tu re on the basis of the cr i ter ia p r e s e n t l y used for the ident i f ica t ion of the var ious clay minerals . The above three "c l ay minera l s" are n a m e d because of their t yp i ca l behav ior using the s t a n d a r d glycerol , heat , ac id solubi l i ty , and washing techniques to eva lua te the in t e r l aye r compound s tab i l i ty . The conver ted ma te r i a l b y h y d r o t h e r m a l synthes is deve loped two to four orders charac ter i s t ic of the d(0Ol) of the newly synthes ized mater ia l . I t appears t h a t the sequent ia l change f rom A1 ion to h y d r a t e d A1 ion to AI(OH)~ occurred wi th the increas ing A1 concent ra t ion . A n equiva len t "Fe -ve rmi - cuhte" was fo rmed in the hema t i t e for g ibbsi te subs t i tu t ion in the 1958 exper iments .

REFERENCES

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Chancy, P. E. and Oxford, W. F. (1945) Chemical treatment of drilling fluids: A. & M. College o/ Texas .Bull. 96, pp. 30-56.

Chancy, P. E., Oxford, W. F., and Chisholm, F. (1954) The chemical treatment of drilling fluids: World Oil, v. 138, no. 1, pp. 107-116; no. 2, pp. 116-126.

Claringbull, G.F. and Hey, H. H. (1952) A re-examination of tobermorite: .Min. Mag., v. 29, pp. 960-962.

Gard, J. A. and Taylor, H. F. W. (1957) A further investigation of tobermorite from Loch Eynort, Scotland: Min. Mag., v. 31, pp. 361-370.

Graham, R. P. and Sullivan, J. D. (1938) Critical studies of methods of determining ex- changeable bases in clay: J. Amer. Ceram. Soc., v. 21, pp. 176-183.

Gray, G. R., Neznayko, M. and Gilkeson, P.W. (1952) Some factors affecting the solidifi- cation of lime-treated muds at high temperatures : Amer. Petro. Instit. Drilling and Pro- duction Practices, pp. 73-82.

Grudemo, A. (1955) Electron (microscope) studY of morphology and crystallization pro- perties of calcium silicate hydrates: Svenska Forskningsinst. Cement .Beton9 rid Kgl. Tek. Hogskol. Stockholm, Handl., no. 26, pp. 1-103: Ceram. Abstr. 1956 pp. 232g.

Heller, L. and Taylor, H. F. W. (1951) Hydrated calcium silicates, II. Hydrothermal re- actions: Lime: silica ratio 1 : 1: J. Chem. Soc., pp. 2397-2401.

294 NINTH NATIONAL CONFERENCE OX CLAYS AND CLAY MINERALS

Heller, L. and Taylor, H. F .W. (1952) Hydrated calcium silicates, III . Hydrothermal reactions of mixtures of lime: silica molar ratios 3 : 2. J. Chem. Soc., pp. 1018-1020. IV. Hydrothermal reactions: Lime: silica ratios 2 : 1 and 3 : 1 : J. Chem. Soc., pp. 2535-2541.

Heller, L. and Taylor, H. F .W. (1956) Crystallographic Data /or the Calcium Silicates: Dept. Sci. and Ind. Research., H. M. Stationery Office, London.

Kalousek, G. L. (1957) Crystal chemistry of hydrous calcium silicates. I. Substitution of aluminum in lattice of tobermorite: J. Amer. Ceram. Soc., v. 40, pp. 74-80.

Kalousek, G. L. and Prebus, A. (1958) Crystal chemistry of hydrous calcium silicates, III. Morphology and other properties of tobermorite and related phases: J. Amer. Ceram. Soc., v. 41, pp. 124-132.

Larsen, D. H. (1955) Use of clay in drilling fluids: in Clays and Clay Technology, Calif. Div. Mines, Bull. 169, pp. 269-281.

McConnell, J. D. C. (1955) The hydration of larnite (beta Ca2Si04) and bredigite (alpha l CasSiO4) and the properties of the resulting gelatinous mineral plombierite: Min. Mag., v. 30, pp. 672-681.

Megaw, H. D. and Kelsey, C. H. (1956) Crystal structure of tobermorite: Nature, v. 177, pp. 390-391.

Morey, G. M. and Ingerson, E. (1937) The pneumatolytic and hypothermal alteration and synthesis of silicates : Econ. Geol., v. 32, pp. 607-760.

Taylor, H. F. W. (1950) Hydrated calcium silicates, I. Compound formation at ordinary temperatures: J. Chem. Soc., pp. 3682-3690.

Taylor, H. F. W. (1959) The dehydration of tobermorite: Clays and Clay Minerals, Proc. 6th Nat. Conf., pp. 101-109.

Taylor, H. F. W. and Howison, J. W. (1956) Relationships between calcium silicates and clay minerals: Clay Min. Bull. v. 3, pp. 98-11.