cutting description guidelines2

8/13/2019 Cutting Description Guidelines2

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CUTTING DESCRIPTION GUIDELINES...............................................................2

Cutting preparation........................................................................................................................................2

Sample quality : At the Shale shakers..........................................................................................................2

Sample quality : Cuttings representativeness...............................................................................................2

Large volume of cuttings requirements....................................................................................................2

Cuttings poorly representative .................................................................................................................3

Sample quality : the cutting cleaning ...........................................................................................................3

Check always the top sieve.......................................................................................................................3Water ase mu! cuttings cleaning............................................................................................................"

#il ase mu! cuttings cleaning................................................................................................................."

Sample quality : the lag !epth .....................................................................................................................$

Sample %uality Check list............................................................................................................................$

&rying the cuttings.......................................................................................................................................$

'ackaging the cuttings..................................................................................................................................$

Calcimetry.....................................................................................................................................................(

Cutting description method...........................................................................................................................7

)acroscopic as well as )icroscopic............................................................................................................*Systematic Cutting &escription )etho!.......................................................................................................*

+eneral Sequence of &escription ............................................................................................................,

+ui!elines for cutting !escription............................................................................................................,

-stimating 'ercentage .........................................................................................................................,

&escription sequence............................................................................................................................/ock name........................................................................................................................................

Color.................................................................................................................................................

+rain Color ...................................................................................................................................01

ar!ness.........................................................................................................................................00

Cutting shape..................................................................................................................................00

+rain Color Shape 4 Surface Si5e Sorting.................................................................................03

Cementation 4 matri6....................................................................................................................0$

'orosity7'ermeaility.....................................................................................................................0(Accessory )inerals 4 unusual features.........................................................................................0*

y!rocaron shows........................................................................................................................0,

Last advice.....................................................................................................................................................18

Cement........................................................................................................................................................0,


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Cutting description Guidelines

Cutting preparation

8he est lithologist will have a little performance if he !escrie unreliale sample.

A goo! an! simple a!vice efore to start the cutting !escription 9o is to walk aroun!the shale shakers an! to oserve the sample catcher in his sampling activity.

Sample quality : At the Shale shakers

8he screens use! are ranging from "1 to 211 meshes 1.1*$ to 1.3,mm;.

8he screens commonly use! are the 01170$1 meshes. With these screens you will enormally ale to !istinguish silts or very fine quart5 grains from your cuttings.

Anyway if !espite /#' LW& an! gas in!ications you are unale to i!entify san!s or

silts in cuttings ask for a check sample from the !esilter.

Sample quality : Cuttings representativeness

nfortunately large volume of cuttings requirements for collection happens in the small

si5e! reservoir section.

Check if the sample catcher concern is only how to get the volume requeste! for

collections an! not how to collect accurately samples.

%&plainto each )u!loggers e6actly how you want the sample caught.


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A'normal case particular event such mu! returns overflow inopportune flushing of

cuttings y !errickman etc?

Ask the sample catcher to collect you a sample for cuttings !escription at the ne6t

reliale !epth it can e 0m after if the planne! sample !epth is misse!;.

@or collection its etter to miss some samples than to fill half all the ags of coursegiving the priority to the 8#8AL collection over the partners or the local7nationalorgani5ation;.


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Water ase mu! cuttings cleaning

Cutting cleaning is often performs y 9etting with pressure! water.

'rolems:

igh gel mu!s !ifficult to wash ask the mu! logger to clean with light touch an! not

to squash cuttings the cutting shape is important information.


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Sample quality : the lag depth

8he lag !epth accuracy is a function of the goo! appreciation of the volume of the si5e of

the open hole part of the well.

Iecause mu!loggers can only un!erestimate the orehole si5e errors from inaccurate lag

!epth will cause a !elay in the arrival of the Bin !epthD cuttings. 8his will also affect therepresentativeness of the cuttings. Accuracy of the lag !epth can e checke! while

!rilling with gas returns.

@rom time to time use the opportunity of the connection gas air slug; to verify the

precision of the lag !epth correction. 8his has to e !one particularly after large cavings

pro!uction or san! pro!uction these 2 events eing a typical consequence of washouts.


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Calcimetry

8he calcimeter recor!s a volume of C#2per minute pro!uce! y the Cl reaction on the

caronate molecules. 8his volume is translate! in G relative to a stan!ar! reaction

etween a pure limestone pow!er an! the Cl.

CaC#3F 2 Cl CaCl2F 2# F C#2or with )g C#3;

8he C#2volume is linke! to the quantity of C#3= = ions.

8he volume of C#2e6presse! in G; otaine! after 0 is suppose! to represent the pure

calcitecontent.

Iecause the reaction is slower for the !olomite after 3 the percentage or C#2volume;is suppose! to represent the dolomitecontent.

Iasic rules for a goo! 9o:

Check if the mu! logger cleans well the cuttings #I) +lycol mu!;.

Check the crush !rie! cuttings nee!s to e finely an! homogeneously pow!ere! toallow a goo! an! homogeneous aci! reaction.

Check if the calcimetry sample weight is constant an! accurate.


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Cutting description method

)acroscopic as /ell as )icroscopic

As well as !escriing in!ivi!ual samples the Wellsite +eologist shoul! also look at the

roa!er view. Lay out sample trays on a ench in the unit in !epth or!er. Iy !oing this

sutle color or te6ture changes can e seen which may e misse! in in!ivi!ual samples.


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+eneral Sequence of &escription

8he sequence of !escription of cutting samples shoul! follow the same stan!ar! routine:

0. Look at the sample tray without the microscope. Are the various lithotypes

easily !istinguishaleJ -nsure there is sufficient sample on the tray an! that itis a ma6imum of one layer thick.

2. 'ut the sample tray in the >K o6 is there any fluorescenceJ


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-escription sequence

!ock name: San!stone siltstone etc.

Color: >se stan!ar! color charts

$rain Color: )ainly applies to san!stones

0ardness: ow resistant are the cuttings to applie! force

Cuttings Shape: +eneral shape of cuttings

$rain Sie: >se stan!ar! grain si5e charts mainly san!stones

$rain Shape sur*ace: >se grain shape 4 surface chart mainly san!stones

Sorting: >se sorting chart mainly san!stones

Cementation3)atri&: 8ypes of cement an! matri6

orosity3ermea'ility: /aw visual !eterminations only

Accessory )inerals: +lauconite micas etc with some qualifier as to aun!ance

4nusual 5eatures : )icrofossils fissures etc.

0ydrocar'on Sho/s: See gui!elines

!ock name

Color

Color is use! as simple !iagnostic tool to ai! in mineral an! environmental !etermination

an! can e use! also for correlation.


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0ardness

8his category is inten!e! to characteri5e the !egree cementation an!7or compaction of thelithology an! how the sample fractures. 8o !etermine har!ness for each lithotype you

will nee! to crush a numer of cuttings using a pro! or twee5ers.

8he common a!9ectives use! to !escrie har!ness inclu!e:

Loose lse +rains !esaggregate when the sample !ry. ot use! on clay7shale.

@riale fri Loose grains can e separate! y pressure from the finger.

@irm frm +rains can e separate! with a pro!

ar! h! +rains !ifficult to !etach pressure result in cutting reaking grains.

Kery ar! v.h!


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Common !escriptive a!9ectives use! for cuttings shape are:Amorphous amor o shape generally !ue to hy!ration of

sample preferre! fracture orientation maske!

Ilocky lky Square angular appearance with no preferre!

fracture orientation

'laty plty @lat appearance with roun!e! e!ges preferre!

fracture plane

Sufissile sfiss @latter an! more elongate than platy not assharp e!ges as fissile preferre! fracture plane

@issile fiss +enerally flat an! elongate with sharp e!gesmarke! fracture orientation

'ressure press


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$rain shape Sur*ace

@or grain surface !escription the common terms use! are:

'itting Small holes on surface grains chemical !issolution or physical impacts;.

Staining n!er inocularv.fine grains are 9ust visile an! silts are

arely visile.

+rain shape an! sphericity give an in!ication of thematurity of the san!stone. owever these can e

affecte! y later mineralisation so that the original

grains are ero!e! coate! or overgrown.

Any evi!ence for this nee!s to e !escrie as it will

effect grain shape an! porosity an! permeaility


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$rain sorting

Cementation matri&

8he most common cements are:

CalciteCaC#3; Will react strongly with !ilute 01G; hy!rochloric aci!. 8he

cutting shoul! !isintegrate into constituent grains as cement

is !issolve!. ote crystal si5e if visile.

-olomiteCa)gC#3;2 as slower reaction with 01G hy!rochloric aci! quicker

with 31G. Calcimetry will give you in!ications.

SilicaSi#2; Cement ut may grow in optical continuity with quart5

grains overgrowth; an! can e !ifficult to spot. Look for

resi!ual surfaces flat crystal surfaces in %t5 grains. Assumesilica cement if no reaction with aci!

Siderite@eC#3; &ull yellow rown an! white will react slowly withapplication of aci!. /elatively rare as cement.

yrite@eS2; Iright yellow gol! an! metallic ut relatively rare.

8he most common matri6 material in san!stone is silt an!7or argillaceous material.

;aolinite is also common an! generally appears as a soft to firm an! white clayey

material ut shoul! e reporte! as cement.


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orosity3ermea'ility

'orosity an! permeaility in !rille! cuttings are !ifficult to evaluate an! are !etermine!at est only very su9ectively. 8ake a goo! look at numer of samples an! cuttings an!

see how well they are cemente! or if there is a common matri6. Sorting also affects

porosity an! shoul! e evaluate! first as it may e a porosity in!icator.

8-S8: select pieces an! let them !ry out porosity may then e estimate! y placing a

!rop of water on a !rie! cutting while viewing through the microscope.

8he spee! at which the water is asore! y the cutting will help in su9ectivelyevaluating porosity an! permeaility. 8his test is useless with #il ase mu! in this case

estimate of porosity will e only visual.

8he scale of estimate is as follows:8race 8r 1=$G

'oor 'r $=01G

@air @r 01=21G

+oo! +! 21=31G


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Accessory )inerals unusual *eatures

Common accessory minerals are:

$lauconite +lauc. &ark green green lack generallyroun!e! grains especially if recycle!.


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0ydrocar'on sho/s

8his section will e !etaile! apart.

Last advice

8he most !ifficult 9o for the cutting !escription is to i!entify an! select thelithotypes i.e. the constant cutting facies which represents the facies variation of

your formations. We know y e6perience the neary limit of our geological an!

se!imentological e6pertise at the wellsite.evertheless we are all ale to !escrie simple things such san!s shales an! for

gra!ational facies !escrie how is the evolution. We are also all ale to report the

presence an! the frequency of very interesting environmental markers such ascaronaceous material ioclasts color change grain si5e sorting grain shape

accessory minerals etc?

A goo! san! 7 shale percentage ratio well !escrie! as per gui!elines is alwaysetter than a complete pseu!oscientific an! neulous lithological !escription

involving " or more lithotypes.So the est a!vice will e:

e simple in your general lithotype selection( 'ut very accurate and detailed

in their description.

&ont spen! ages !eci!ing on e6act percentages.

ever let the acklog of sample accumulate not only is it !ifficult to catch up ut

the )u!loggers get short of trays. Always !escrie samples on the metal trays.

Cutting samples are collecte! wet from the shale shaker. Samples shoul! e!escrie! whilst still wet an! shoul! not e left to !ry out or re=hy!rate! with

water. 'ut samples in plastic ags or at least cover them up if it is to e sometimeefore they are !escrie!. owever the te6ture of certain formation types can e

seen more clearly when !ry so occasionally keep a portion of sample for later

!ry e6amination.

+et the )u!loggers to have representative samples of all potential mu! a!!itives

that may e use! in the well.

cutting description guidelines2

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