geological desciption(simple way to describe)..special

8/9/2019 Geological Desciption(Simple Way to Describe)..Special

http://slidepdf.com/reader/full/geological-desciptionsimple-way-to-describespecial 1/8

How to Describe sample while on wellsite job:

First we need to tell about the rock type then we have to follow the trend as per client requirement. Here are

some common rock types.

CLS/MDST/SLST

1. COLOUR

I.e. me ! "#$! "#% ! "# br$! "#% lt "#% ! brn% bl!% bl&% brn% clss% cr 'cream(% "o% "rn% op 'opa)&e(%

or% p!% p&rp% re% *i% wh% #el% *aricol% mot.

+. H,RD-SS 'CO-SOLD,TO-(

s0t soft Grains offer no resistance when prodded

0rm firm Gns bk apart easily

mo h mod hard Gns bk with some difficulty

h Hard Grains diff to bk

brit brittle (bk easily along fracture planes) ie !oal or salt

cons consolidated&ncons

ol

unconsolida

ted

plas plastic Fle" without breaking

. 2R,CTUR '3R,4(

bl!# blocky #reak into rectangular fragments

an" angular $a%ority of corners are less than &' deg

splt# splintery ointed elongated cuttings

0is fissile Fine grained sediments tend to divide readily along

well developed laminar or platy structure

s&b0is subfissile *s above+ but not so well pronounced

amor amorphous ,o form - commonly to describe soft cuttings

conch conchoidal !urved ribbed surface+ like a shell

cr&mb crumbly crumbles

. T5TUR 'to escribe *is&al appearance(

erth# earthy

homo" homogenou

s

/ock with a uniform appearance ie 0plain mudstone1

hetero" heterogeneo

us

Ie 0sandy mudstone1 or 0conglomerate1

*esic vesicular 2mall s pherical cavities+ like an aero.


ch!# chalky *ppears chalky

6ln crystalline *ppears "ln

s&c sucrosic *ppears sugary

w6# wa"y *ppears wa"y

0ri friable !an be disintegrated into individual grains by finger

pressure

lam laminated *ppears laminated

w6# wa"y

0ri friable

3. SLT CO-T-T



ie sl slt#% loc slt# or w occ *0 )t7

*renaceous !425 that has a recognisable sandy content -

appearance - te"ture

8. C,R3O-,T CO-T-T 'cr&sh c&ttin"s(

non% sl% * or occ sl

calc

calcareous 5he way in which a cutting reacts in 6'7

H!4

dolomitic /eacts only after several mins immersion

i.e. occ sl calc or * ol

-.3. an oil base m& inhibits reaction% so cr&sh c&ttin"s to e6pose 0resh s&r0aces.

9. SLL-;

swl" / non swl" 2well 8 (,# hydro 9 hygro used with same meaning)

H#"t Hydroturgid 8 swelling in a random manner- imm

e"pands-throughout sampleH#"clst Hygroclastic 8 bits break off in water - patchy swelling

H#"0is Hydrofissile 8 swells into sm flakes :sl;+ :mo; or :*;

Cr#ptt !ryptoturgid 8 swells in dilute H!4 hot water

Cr#pt0is !ryptofissile 8 as 0Hygro1 but induced by 6'7 H!4

<. ,CCSSOR= COM>O--TS (2mall quant1s of other minerals present)

issem 8 fine grains throughout

no 8 crystalline mass

r tr 8 rare trace of ab&n 8

abundantloc 8 locally occ 8

occasionally

mica

"la&c

micromic 8 micromicaceous

SST

1. -,M O2 ROC4 225 (cemented sand grains) or 2,< (sand)

+. COM>OSTO-... =5>+ ark (sig quantities of Feldspar)+ lith (sig rock fragments)

<! bits churn wellcemented sandstone into /k Flr+ so acid test may look like 425. 4ook for grains ofsand trapped within the paste.

If predominantly recovered as /ock Flour then start with SST: rec as R! 2lr%

If predominantly 225 then start with SST: and state finally also rec* as R! 2lr% (if applic).

If predominantly grains and some /k flr then start with SST: lse )t7 "ns?..also rec* as R! 2lr.

. COLOUR

I.e. clss% clr to transl% transp$transl% loc pale "r# or pale "r# brn% 0rst

(abraded outer surface)

?. H,RD-SS 'CO-SOLD,TO-(



0ri friable (in place of soft or firm)

lse loose @here 0only1 sand grains are observed

brit brittle (bk easily along fracture planes) i.e. !oal or salt

cons consolidated

&nconso

l

unconsolida

ted

@. 2R,CTUR / 3R,4 ' to escribe morpholo"# o0 c&ttin"s(



splt# splintery ointed elongated cuttings

0is fissile Fine grained sediments tend to divide readily along well

developed laminar or platy structure


amor amorphous ,o form - commonly to describe soft cuttingsconch conchoidal !urved ribbed surface+ like a shell

cr&mb crumbly * cutting of irregular outline

8. ;R,-S

Grain type (if

app)

Asually =uartB+ Ccc *rkosic (sig quantities of F-spar difficult

to spot) or 4ithic (sig rock fragments)

Grain 2iBe *0% 0% me% c% *c ie A *0 to occ mB

Grain !olour

(if applic)

wh% clss% transl% transp% #el% or % 0rst (abraded outer surface).

Grain 2hape

(or roundness)

an"% s&ban"% rn% s&brn% well rn ie As&ban" to s&brn% loc

rnB

Grain

2phericity

sphr% s&bsphr% elon"% s&belon" ie As&ban" to s&bsphrB

Grain 2orting 'Little *ar well srt(% mo srt% pr srt% bimo srt ie @/@ Apr

srtB

9. CM-T,TO- 'in terms o0 e"ree an t#pe(

!ement

type

0how

easily canthe bond

be

brokenD1

quals areE

r% occ% pr%

mo%

well% str

Lse loose ,o cement

Sili 2ilica no react with

H!4

r sili cem% loc slt#

Cal !alcite usual reaction occ with str calc cemDol

<olomite

dolomitic

reaction

<. MOD2RS

2and is *rgillaceous

ar"

,on !425 with a recognisable clay content

!lst is *renaceous

aren

,on 225 i.e. !425 that has a recognisable sandy

content - appearance - te"ture

!onglomeratic 225

225= =uartB

225* *rkosic ar! (sig quantities of Feldspar)

2254 4ithic li (sig rock fragments)



2mall

quant1s of

other

minerals

present

tr p#r $ight be issem (fine grains throughout) or no

(crystalline mass) ie 0

Cther e"amples are? rtr mica or ab&n mica an "la&c or occ

mica or loc "la&c or no "la&

E. >OROST= 0e"tremely sub%ective1

*is por visible porosity Ie 0" *is poroB or 0no *is poroB

int6ln Intercrystalline

intra6l

n

Intracrystalline

int"ran Intergranular

intra"r

an

intragranular

TH- ;O O-TO SHOSF

LST (wash salts with base oil only to avoid dissolving)

!*/#C,*5S (composed of lime mud and-or biogenic debris)*C/I52 (ie Gypsum-*nhydrite)

,0ter etchin" can place sample in col ,la7arin Re 0or a 0ew mins. LMST eep re% DOL

&na00ecte

+. COLOUR (specifically the colour of the rock)

I.e. lt brn "r% brn "#% bl&/wh% "#$o00 wh.

. CO-SOLD,TO-

s0t soft Grains offer no resistance when prodded

0rm firm Gns bk apart easily

mo h mod hard Gns bk with some difficulty

h hard Grains diff to bk

brit brittle (bk easily along fracture planes) ie !oal or salt

cons consolidated

&ncons

ol

unconsolida

ted

plas plastic Fle" without breaking

lse loose 4oose

0ri friable asily crumbled

?. 2R,CTUR SH,> 'to escribe morpholo"# o0 c&ttin"s(



splint splintery ointed elongated cuttings

0is fissile Fine grained sediments tend to divide readily along well

developed laminar or platy structure



conch conchoidal !urved and ribbed surface+ like a shell

cr&mb crumbly !rumbles

@. T5TUR 'to escribe *is&al appearance(



micro6l

n

$icrocrystall

ine

Cnly visible under microscope

6ln crystalline asily visible crystal structure

cr#pto6

ln

cryptocrystall

ine

!rystalline in appearance but no visible structure

(commonly applied to !hert)

s&c sucrosic Fine grained rock with sugary appearance

ool oolitic @hen contains spheroids of algal origin

erth# earthyhomo" homogenous /ock with a uniform appearance ie 0plain mudstone1

hetero" heterogeneou

s

Ie 0sandy mudstone1 or 0conglomerate1

*es vesicular 4ike an aero


ch!# chalky *ppears chalky

lam laminated *ppears laminated

@'a(. DU-H,MS CL,SS2C,TO- '2OR LMSTO-S(

3,SD O- >RO>ORTO-S O2 LM MUD TO S4LT,L 2R,;M-TS

$udstoneMst

!omposed of lime mud ('m) 9 less than 6'7 grains. $udsupported

@ackestone

!st

:!C*/2 G/*I,2 F4C*5I,G I, $*5/IJ; !omposed

mainly lime mud w more than 6'7 grains (K'm). $ud suptd

ackestone

>!st

:G/*I,2 I, !C,5*!5 @I5H $*5/IJ; !omposed mainly

grains 9 grain suptd. K6'7 interstitial mud matri" 9 occ sparry

calcite or pore space

Grainstone

;rst

:G/*I,2 @I5HCA5 $*5/IJ; !omposed of grains 9 grain

supported. 4ess than 6'7 interstitial mud matri"

#oundstone

3st

Criginal constituents bound 9 suptd by organic growth

!rystalline

5ln

*ll orig te"tures lacking due to recrystallisation. <istinct

crystal faces

8. MOD2RS

*rgillaceous

ar"

,on claystones with a recognisable clay content

*renaceous ,on claystones with a recognisable sandy content

<olomitic ol

*nhydrite anh#

2iliceous sili

9. ,CCSSORS

2mall quant1s

of other

minerals

present

tr

p#r

$ight be issem (fine grains throughout) or no

(crystalline mass)

Cther e"amples are? rtr mica or ab&n mica an "la&c or occ

mica or loc "la&c or no "la&c

*nhydrite

<olomite

4imestone often contains carbonaceous lamination of algal origin

<. >OROST= 0usually isible or stimated1(visual estimation is very sub%ective)



*is por visible porosity Ie 0nil (or pr+ or fr or mod or gd or v gd or e"c) vis

poro1

int6ln Intercrystalline

intra6ln Intracrystalline

int"ran Intergranular $ay be seen in oolitic limestones

intra"ra

n

Intragranular

0r Fracture Is the principal type*&" uggy @here elements of original fabric have been

leached away by ground water

E. OOLTS/>LODS

S>H% SU3S>H+ (2!IFL 2I> /*,G)

SHOS

1. ST,-

If free oil in sample then give 7

is there an oily smellD"amine cuttings for oil staining under microscope (what colour in sample tray).

!ould beE spty+ streaky+ pch+ uniform. Ie 01G spt# stn1 or 0no *is stn1 or 0@G pch stnB or 0"enerall#

wea! 1 or 0wea! to 0airB or Apale br oil stain% &ni0ormFbrt bl&ish white 0l&orB

+. 2LUORSC-C 'nat&ral(

"amine washed cuttings under A light and describeE

'a( ,mo&nt: in 7

'b( ntensit# o0 0l&orescence: v dull+ dull+ mod+ bright

' c( Colo&rsE :bluish white condensate;+ :white;+:yellow;+ :gold;+ :green;+ :orange heavier oil;+ :brown

heavier oil;+ :black in bitumen 9 dead oil;

,oteE base oil gives off a pale blue fluorescence (keep a sample in A bo")ie A<G &ll #el fluor1 or AEG brt #el wht 0l&orB

'( Distrib&tion: i.e. patchy+ evenly.

lace representative cuttings in spot tray to check they are 225 and not !a!CM

. SOL-T ACUTB (should really list type ie normal+ dried+ acid+ water)

2pot tray back in A and (while watching) immerse cuttings in trichloroethane+ describeE (as it is leached

from rock)

'a( Rapiit# 8 instant+ fast+ mod fast+ mod+ mod slow+ slow

'b( Character 8 diffuse+ blooming+ streaming

'c ( Colo&r 8 br+ orange+ gold+ bright yellow+ gy yel+ yel wht+ blu wht.

ie Amo$0st strm"%bl& wht c&t 0l&orB

?. CRUSH CUT

If leaching is v slow+ then crush cuttings and observe changes in fluorescence.

could use fresh sample

@. Resi&al Rin" <escribe colour of oil stained solvent under natural light

allow solvent to evaporate and describe colour of residual ring

ie Ath! res rn"% abnt O in m&% str pet orB OR Ano res rn"% mo O in m&% no pet oBor Aocc pale br

resi&eB

residual ring 8 none+ trace+ thin rng+ mod rng+ thick ring+ thin film+ thick filmoil in mud 8 trace+ mod+ abnt

odour 8 str+ mod+ tr+ none



CHEMICAL TESTS

ith 1G HCL etch

4imestone 8 instant 9 violent - float 9 move around - comp dissolve in mins - leaves acid frothy

<olomitic 4imestone 8 immediate reaction - moderate 9 continuous - move from top to bottom of acid

!alcitic <olomite 8 slowly 9 weakly - accelerates to continuos reaction after few mins - some bobbing on

bottom

<olomite 8 slow 9 hesitant - bubbles evolve one at a time - may have to warm acid for reaction to proceed -

leaves acid milky.

ith ,la7arin Re etch 'a0ter HCL( leave in cold *laB /ed for a few minutes

4imestone 8 <eep red

<olomite 8 Anaffected

!alcite 8 /ed

Ferrous !alcite 8 $auve

Fe rich !alcite 8 urple

Fe dolomite 8 4ight #lue

ith 3ari&m Chlorie test (#a!4) (for evaporates)

6. lace several cuttings in bottle and fill with distilled water.

. *gitate and pour off water.

M. /efill and repeat.

. Half fill with distilled water+ add M drops of H!4 and agitate.

3. *dd drops #a!4

N. ,ote discoloration if any.

*nhydrite 8 white precipitate

Gypsum 8 pearly white discoloration

>henolphthalen 8 redcement

Heatin" will cause

<olomite !laystone to effervesce when heated but will produce lots of particles and the cement dissolves.

<olomite will stay solid and bubble.

T#pes..

er# er# 2ine Cla#stone less than 6-Mrd 2ilt

er# 2ine M&stone between 6-Mrd 9 -Mrds 2ilt:less than m; e"tremely fine grain+ homogenous appearance+ smooth 9 fine+ feels greasy to touch+ not gritty

between teeth. $ :greater than 3'7 !lay then *rgillaceous;

Shale a 0catchall1 category where there is more than 6-Mrd !lay and unknown quantity of 2ilt. *lso when a

fine sediment becomes laminated. :less than m;

2ine Siltstone more than -Mrds 2ilt

less than M7 clay+ more than NO7 silt siBe perticles :N'm;

grainy+ though generally grains are not vis to naked eye+ feels gritty between teeth+ has greater than 3'7 2ilt

content. !rush few crumbs with pencil in dish. If feels grainy is silt

,r"illaceo&s Roc!s 0the most abundant sediment1

primarily marine depositional+ though can be lacustrine or f-water

Shales+ well compacted and fissile



Cla#s+ soft and amorphous

Marls(!arbonate bearing clays).calcareous shale

Siliceo&s Roc!s 0small 7 of seds1

Siltstones smaller than the smallest sst grains

Sans silica grns+ fldsprs P other minerals

Sanstones

Cla#stone/M&stone

e"tremely fine grain+ homogenous appearance+ smooth 9 fine+ feels greasy to touch+ not gritty between teeth.

:less than m;

:greater than 3'7 !lay then *rgillaceous;

If becomes laminated then is Shale :less than m;

Siltstone :N'm;

grainy+ though generally grains are not vis to naked eye+ feels gritty between teeth+ has greater than 3'7 2ilt

content

Sanstone (coarse) crush few crumbs with pencil in dish. If feels grainy is silt

Cr#stal 2orms

*nhedral no visible crystal form

2ubhedral partly developed crystal form

uhedral well developed crystal form

Clastic Roc! T#pes

/udaceous 5ill?..Gravel

*ranaceous 2ilt?..2and

*rgillaceous $ud?..!lay

geological desciption(simple way to describe)..special

Documents