coring (diamond) technology

8/12/2019 Coring (Diamond) Technology

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DIAMOND CORINGTECHSWahid Mia, Manager (Geology)

B A P E X

Defination of CoresA core sample, or simply core, is a section of roc c!t o!t (or cored) from a geological formation "y

core drilling# $n another %ay, a core is a sample of roc in the shape of a cylinder# &aen from the side of

a drilled oil or gas %ell, a core is then dissected into m!ltiple core pl!gs, or small cylindrical samplesmeas!ring a"o!t ' inch in diameter and inches long# &hese core pl!gs are then dried and meas!red#

Types of Cores

&here are seeral types of cores that can "e recoered from the %ell, incl!ding a) f!ll*diameter cores, ")oriented cores, c) natie state cores and d) side%all cores#

a) Full-diameter cores:+anging in sie from appro-imately '#./ to /#0/ inches (11#/ to '#1 mm) in

diameter and a"o!t 02 to 122 feet (3#' to '0'#4 m) in length, a f!ll*diameter core is the typical coring

sample that is taen from a %ell# Beca!se reseroir rocs that are highly fract!red, and th!s ery poro!s,are not retained in the core "arrel, loss of core can "e a ery strong sign for the reseroir roc#

b) Oriented cores:5riented cores are mared %ith a grooe along the length of the sample to indicate

the geographic or magnetic north#

c) Native state cores:$n an effort to contain all the fl!ids in the core !nder reseroir conditions, natiestate cores are "agged, or encircled "y a r!""er sleee as the sample is drilled#

d) Sidewall cores:A less e-pensie and less time*cons!ming option to o"tain a core sampling, side%all

coring inoles retrieing seeral small core samples meas!ring appro-imately ' inch in diameter and'#./ inches long#

Coring Fluids: Modern coring6drilling fl!ids are !sed d!ring most coring operations# 7o%eer, if

determination of endpoint sat!rations is one of the o"8ecties, a coring fl!id is designed to maintain theimmo"ile phase sat!ration# $f a core is to "e !sed to define fl!idsat!ration dependent parameters, s!ch as

relatie permea"ility, capillary press!re or electrical properties, the drilling fl!id sho!ld "e form!lated to

maintain core %etta"ility characteristics as they %ere in the reseroir# 9ore handling : preseration


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proced!res are designed to maintain the physical integrity : reseroir %etta"ility !ntil planned tests are

completed# &he ideal coring program considers roc type, degree of consolidation : fl!id type# $t

minimies physical and chemical alteration of the roc and can incl!de specialied press!re, sponge orgel coring systems#

&he selection of a coring fl!id sho!ld "e "ased on fo!r points; a# l!ids red!ce %ear on drilling and coring "its "y cooling# >l!ids remoe c!ttings : rocflo!r# +ecirc!late to filter fl!ids and to minimie impact on enironment#

Core arrels

&o collect the core of the roc drilled, a deice no%n as the core "arrel is !sed# 9ore "arrel retains roc

core samples from drilling operations# $ts length aries from 2#/ to m# &here are three types of core"arrel in !se; i) &he single t!"e core "arrel, ii) ?o!"le t!"e core "arrel : iii) &ripple t!"e core "arrel

i) Single tube core barrel@ Most r!gged, least e-pensie 9onsists of head section, core recoery t!"e,reamer shell : c!tting "it 5ften !sed as starter %hen "eginning core operations 9oring in homogeneo!s

hard roc (%here the core does not %ash a%ay or cr!m"le easily) and penetrating roc layers a"oe the

strata (%here high core recoery is not essential)#


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b& Face Disc%arge: >ace discharge core "its are designed to diert some fl!id that %o!ld normally pass

thro!gh the throat of the "it to the face of the "it# &his cleans the face of the "it and red!ces the amo!nt of

fl!id sco!ring the core as it enters the core "arrel#

c& 'ow-(nvasion "rofile; &he lo%*inasion profile coring "its are designed to ma-imie penetration rate

: minimie drilling fl!id filtrate inasion into the core# &he design incorporates face discharge ports, a

red!ced n!m"er of c!tters, and a diminished clearance "et%een the inner core "arrel : the "it face#Core Catc%ers

&he core catching deices are hollo% "arrels to catch the core, need "all or rod to close the catcher# &he

single most critical part of eery coring system is the core catcher that holds the core in the "arrel as it is"ro!ght to the s!rface# &here are many types of core catchers, e#g#, split*ring, spring, collet, slip, dog or

flapper, "aset and f!ll*clos!re etc#

Coring its

9ore "it is an ann!lar (do!ghn!t*shaped) diamond "it to c!t the core# $t is a "asic part of the coring

system# With a little "acgro!nd information, it is possi"le to mae informed decisions on c!tter types,"it profile : hydra!lic considerations for the range of anticipated coring conditions# >inal "it selection

sho!ld "e g!ided "y the goals of the coring program, co!pled %ith a confirmation that the "it has proenitself in the field for similar applications# &he hardness, a"rasiity : aria"ility of the rocs to "e cored

%ill hae the greatest infl!ence on c!tter selection# General g!idelines s!ggest !se of smaller, moreimpact*resistant c!tters as the formations get harder# Ho%*inasion, face discharge core "its designed for

!nconsolidated*to*medi!m strength formations can "e !sed in harder or more a"rasie rocs, "!t "it life

may "e drastically red!ced# &he information presented in the follo%ing ta"le proides an oerie% of thetypes of coring "its that are aaila"le#

+oc Properties +oc &ype 9ore Bit

Fltra*hard, a"rasie roc I!artite, $gneo!s +ocs $mpregnated nat!ral diamond#

7ard, a"rasie roc


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& "olycrystalline Diamond Compact: P?9 drill "it is a ne% prod!ct after the hot*pressed and

electroplated drill "it recent years# &he main feat!res of P?9 "it are; (i) $t has a s!per long life# &he

grinding6cons!mption ratio of P?9 is 02*12 times that of t!ngsten car"ide "it and '2 times that ofdiamond "it# (ii) $t had high drilling speed# (iii) $t can "e operated %ith lo% press!re and lo% speed# (i) $t

has a good gage protection# () $t can "e !sed %idely, more s!ita"le for drilling in the strat!m %ith

formation K . (i) $t has a lo% cost#P?9 c!tters are man*made diamond materials that consist of a layer of micron sied diamond grit

sintered together : "onded to t!ngsten car"ide st!ds# &he thicness of the polycrystalline diamond layer

is only 2#202 to 2#232 inches (2#/' to '#/0 mm)# P?9 "its are !sed to efficiently core formations rangingfrom ery soft to medi!m hard# &he "its are designed to c!t "y shearing res!lting in a rapid +5P# &hey

are s!scepti"le to impact damage for its c!tterLs geometry# &herefore, they are not recommended for ery

hard, highly fract!red, or cherty formations#


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&


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!ow does core sampling complete,

A %ay of meas!ring %ell conditions do%nhole "y st!dying samples of reseroir rocs, core analysis

gies the most acc!rate insight into the porosity : permea"ility, among other characteristics, of the%ell#

$n order to complete a core sample, drilling m!st "e halted at the top of the s!"s!rface of the

reseroir# &he drill*string is remoed from the %ell"ore, the drill*"it remoed and a rotary coring"it is attached in its place#


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Operation:

When the piston corer is !sed from ice, a hole (%ith diameter */ cm larger than that of the corer head)

has to "e drilled# 9ores !p to *1 m length can normally "e lo%ered : raised ertically thro!gh the hole

in the ice# &o retriee long (O*1 m) and heay cores, ho%eer, it is commonly necessary to c!t an o"longtrench in the ice "y means of a chain sa% and6or an ice a!ger# 7o%eer, step ladder placed "y the hole

allo%s one person to clim" s!fficiently high to g!ide the top of the corer#7oles on the PN9 core "arrel for the corer head and core catcher are made "y a hand6po%er drill thro!gh

premade holes on a 8ig#

&he piston %ire rope : the main %ire rope are fed thro!gh the steel pipe : the corer head from a"oe

and attached# ?ish*%ashing li=!id or ac!!m grease is p!t on the piston corer to red!ce friction "et%eenthe piston corer : the PN9 sampling t!"e# &he piston : piston %ire are fed into the PN9 sampling t!"e

"y means of a plastic rod !ntil the piston gets in a position close to the core catcher#

&he main %ire rope is attached to the corer head "efore the PN9 sampling t!"e is fastened to the head#>or e-tra sec!rity, t%o hose clamps may "e fastened 8!st a"oe : "elo% the scre%s at the corer head#

&he PN9 sampling t!"e has then to "e filled %ith %ater thro!gh the o!tflo% hole at the corer head inorder to preent the piston corer from sliding !p%ards in the sampling t!"e d!ring lo%ering of thesampler into the %ater# &he %ater depth at the coring site m!st "e meas!red precisely "y a meas!ring tape

and the depth transformed to the main %ire rope to ens!re to get the soft top sediments# An alternatie

%ay to meas!re the %ater depth is to attach a light plate to the piston corer ("efore the piston is placed on

the %ire) and send it do%n to rest lightly on the sediment s!rface to preent any significant dist!r"ance#An electrical tape is p!t on the %ire rope at the ice s!rface as an e-act meas!re of %ater depth# B!t "y far
http://www.uib.no/norpec/pictures/coring/coring-corer.jpg


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the "est %ay to control the coring operation is to !se echo*so!nding e=!ipment for e-act meas!ring :

monitoring of the process#

&he sampler is lo%ered "y hand do%n to the sediment s!rface "y holding the main %ire rope attached tothe corer head (note; not the piston %ire)# When the lo%er end of the PN9 sampling t!"e is on, or 8!st

a"oe, the sediment s!rface (to get the sediment6%ater interface), the piston %ire is attached %ith a %ire

clamp onto a "olt6cara"iner at the 8ac lifting arm, preenting the piston form entering the sediments#&%o long static ropes are attached to the %eight# When coring in deep %ater ('22*'/2 m) %ires and ropes

tend to t%ist together# &he t%o static ropes may therefore "e replaced %ith one#

&he o"long slit piece on the %eight is remoed "efore attaching the %eight onto "oth %ire ropes thro!ghthe o"long slit on the %eight# &hen the slit piece is attached to the %eight and the %eight can "e lo%ered

to the corer head# Before coring "egins, the length of the PN9 sampling t!"e is mared "y electrical tape

on the main %ire rope attached to the corer head to see %here to stop penetration into the sediments# By

man!ally raising (commonly not more ten '#/ m) and dropping the %eight %ith the t%o static ropes(alternatiely on static rope) thro!gh p!lleys on each side of the 8ac, the PN9 sampling t!"e is drien

into the sediments# Beca!se the closely fitting piston and the sediment s!rface d!ring penetration, the

sediments are s!ced eenly and !ndist!r"ed into the sampling t!"e# When not !sing a piston, the friction

of the sediment inside the core t!"e normally preents more than a fe% decimetres of sediments fromentering the sampling t!"e#

When PN9 sampling t!"e has penetrated the sediments, or the %eight starts "o!ncing %hen reachingimpenetra"le sediments ("edroc, stone, diamicton etc#), the %eight is p!lled !p along the %ire ropes to

the s!rface and laid on ice6raft# &hen, "oth %ires are attached to the %ire clamps on the lifting arm of the

8ac to p!ll the corer o!t of the sediments# When the sampling t!"e is o!t of the sediments, the samplercan normally "e p!lled thro!gh the %ater col!mn "y hand# Before p!lling o!t long cores (O*1 m)

containing mostly minerogenic material, the o"long fiss!re in the ice allo%s grad!al lo%ering of the top

of the sampler# +opes fastened to the corer head and aro!nd the sampling t!"e aid in retrieal#

When coring from a raft, anchoring is necessary to hold station %hile the coring operation is carried o!t#5n a raft the sampler : core t!"e can "e fastened !nderneath "efore going to the lae shore# &hereafter,

the sediment catcher : the corer head are remoed "efore the sampling t!"e is cored and la"elled#

9ores m!st "e transported caref!lly and stored !nfroen in order to preent the sediments form "eingt!r"ated#

&he main adantages of the corer are; '# Hight*%eight (a"o!t '22 g), easily transporta"le on a sno%*

mo"ile sled 0# Easily handled "y (three) persons # &he sampler can core !p to 3 m of sediments in%ater depths to at least 32 m# 1# Hittle of no dist!r"ance of the sampled sediments# /# 5pera"le "oth from

ice : rafts#

&he main disadantages are; '#


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Fig: *dvanced Diamond Core arrel(Schematic of the ADCB showing the bit, outer core barrel & inner core barrel. The ADCB is an adaptation of a mining style "!" coring assembly.

&echni=!es of ?iamond 9ore ?rilling&he process of ?iamond core drilling is of a lo% noise, free from d!st : non*perc!ssie drillingtechni=!e is !sed to mae the smooth holes# &he techni=!es of ?iamond core drilling is needed %hen %e

re=!ire an e-act circ!lar penetration# Fsing this techni=!e yo! can craft holes of any sie : deepness#

&he main category of this techni=!e is +otary : Wire*line# +otary techni=!e is !sed for "orehole as %ellas for coring in rocs# Wire*line is !sed for mineral e-ploration moreoer it intends for not to mae a

hole "!t to salage a core sample#

Diamond core drilling?iamond core drilling (e-ploration diamond drilling) !tilies an ann!lar diamond*impregnated drill "it

attached to the end of hollo% drill rods to c!t a cylindrical core of solid roc# &he diamonds !sed are fine
http://en.wikipedia.org/wiki/Diamond_core_drillhttp://en.wikipedia.org/wiki/Exploration_diamond_drillinghttp://en.wikipedia.org/wiki/Diamond_core_drillhttp://en.wikipedia.org/wiki/Exploration_diamond_drilling


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to microfine ind!strial grade diamonds# &hey are set %ithin a matri- of arying hardness, from "rassto

high*grade steel# Matri- hardness, diamond sie and dosing can "e aried according to the roc %hich

m!st "e c!t# 7oles %ithin the "it allo% %ater to "e deliered to the c!tting face# &his proides threeessential f!nctions * l!"rication, cooling : remoal of drill c!ttings from the hole#

?iamond drilling is m!ch slo%er than reerse circ!lation (+9) drilling d!e to the hardness of the gro!nd

"eing drilled# ?rilling of '022 to '22 metres is common and at these depths, gro!nd is mainly hard roc#?iamond rigs need to drill slo%ly to lengthen the life of drill "its : rods, %hich are ery e-pensie#

9ore samplesare retrieed ia the !se of a core t!"e, a hollo% t!"e placed inside the rod string and

p!mped %ith %ater !ntil it locs into the core "arrel# As the core is drilled, the core "arrel slides oer thecore as it is c!t# An JoershotJ attached to the end of the %inch ca"le is lo%ered inside the rod string and

locs on to the "acend (aa head assem"ly), located on the top end of the core "arrel# &he %inch is

retracted, p!lling the core t!"e to the s!rface# &he core does not drop o!t of the inside of the core t!"e

%hen lifted "eca!se either a split ring core lifter or "aset retainer allo%s the core to moe into, "!t not"ac o!t of the t!"e#

?iamond core drill "its

5nce the core t!"e is remoed from the hole, the core sample is then remoed from the core t!"e andcatalog!ed# &he ?rillers assistant !nscre%s the "acend off the core t!"e !sing t!"e %renches, then each

part of the t!"e is taen and the core is shaen o!t into core trays# &he core is %ashed, meas!red :

"roen into smaller pieces !sing a hammer or sa%n thro!gh to mae it fit into the sample trays# 5ncecatalog!ed, the core trays are retrieed "y geologists %ho then analyse the core and determine if the drill

site is a good location to e-pand f!t!re mining operations#

?iamond rigs can also "e part of a m!lti*com"ination rig# M!lti*com"ination rigs are a d!al set!p rigcapa"le of operating in either a +9 : diamond drilling role (tho!gh not at the same time)# &his is acommon scenario %here e-ploration drilling is "eing performed in a ery isolated location# &he rig is first

set !p to drill as an +9 rig and once the desired metres are drilled, the rig is set !p for diamond drilling#

&his %ay the deeper metres of the hole can "e drilled %itho!t moing the rig and %aiting for a diamondrig to set !p on thepad#

Field SamplingCore Sampling and "reservation: A) +emoal of core from core "arrel B) >re=!ency

of sampling 9) Preseration of core ?) 9ore handling in la"oratory#A) +emoal of the core from a standard inner core "arrel; &he core sho!ld "e remoes from the "arrel in

as small segments in this proced!re for conentional analysis# &he e-tra care sho!ld "e taen to

preent e-cessie "reaing !p of the core# 7ammering : 8arring on the core "arrel is often

necessary# Each piece is %iped clean %ith dry rags (not %ashed) as soon as it is remoed fromthe "arrel, laid o!t on the pipe rac and mared as to top : "ottom# After the entire core is

remoed from the "arrel, the core is meas!red %ith a tape and mared off into feet or meters#Any lost core is logged at the "ottom of the cored interal# $f more cores are meas!red than

s!pposedly is c!t, the operator resoles the discrepancy#

B) >re=!ency of sampling; $n conentional analysis, one sample per foot or meter is ordinarily taen#>ormation %hich o"io!sly non*prod!ctie (e#g#, solid shale) is not sampled# $f the section to "e analyed

is heterogeneo!s, samples may "e taen closer than one per foot or meter# &aing fe%er samples than one
http://en.wikipedia.org/wiki/Diamondhttp://en.wikipedia.org/wiki/Brasshttp://en.wikipedia.org/wiki/Core_samplehttp://en.wikipedia.org/wiki/Drill_floorhttp://en.wikipedia.org/wiki/File:Diamondcorebits.jpghttp://en.wikipedia.org/wiki/Diamondhttp://en.wikipedia.org/wiki/Brasshttp://en.wikipedia.org/wiki/Core_samplehttp://en.wikipedia.org/wiki/Drill_floor


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per foot or meter is not recommended#

>reeing or chilling %ith dry ice * $f the core samples selected for analysis are to "e analyed for fl!id

content, it is necessary that the samples "e presered for transportation to "e la"oratory to preent theeaporation of the li=!ids# &his is normally done "y freeing %ith dry ice (core is in 95 0atmosphere as

ice s!"limes)# (ii) Plastic "ags * this method is recommended for short*term storage, 0* days only to

%rap the samples tightly in plastic "ags so as to e-cl!de air# 9are m!st "e taen to preent p!nct!ring the"ag or e-pos!re to e-tremes of temperat!re# (iii) >oil coated %ith %a- * &his method is sometimes !sed

for conentional samples to %rap them tightly %ith saran : al!min!m foil and coat them %ith paraffin6

%a- or strippa"le plastic# (i) +!""er sleee * 9ores may "e presered "y capping : taping sleee ends#


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coring (diamond) technology

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