Compositions for Controllingi Lost Circulation in Depleted
Reservoirs
FIELD OE' THE IN\ZENTION
t00011 The present inventíon relates generally to oil and gas
reservoirs. Tn particular, the present invention relates to
compositions for controlling l-ost circulation in oil- and gas
TCSCTVOII S .
BACKGROI'ND OF THE IN\¡ENTION
i00021 Oil and gas residing in a subterranean formation may
be recovered by drilling a wellbore into the formation. During
.¡ì . the dritling of a wellbore, various drilling fluids are typicalty
used in the welfbore for a variety of functions including
controlling formation pressures, removing cuttings from the
wellbores, sealing permeabi-e formations encountered while
drilling, cooling and lubricating drilling bit, maintaining
wellbore stability and overall well control. During these above
mentioned functions, the drilling fluids circulate through a
drill pipe and dril-1 bit into the wellbore, and then may
subsequently flow upward through the wellbore to the surface.
[0003] For a drilllng fluid to facilitate the above mentj-oned
functions and to al-l-ow dritting to continue, the drilling fluid
must stay in the wellbore. However, one challenge which is very
commonly encountered during drilling operations is the issue of
lost circulation. In lost circulation, a part or all of t.he
drilling fluid does not return to the surface. The probJ-em
resufts in routine disruption during dril-J-ing operations and has
several consequences like fluid inflow, wellbore coll-apse/
formatlon damage/ nonproductive rig time, and environmental
issues.
t00041 Further, the l-ost circufation poses many challenges to
the petroleum industry especiall-y when drilling highly
permeable, highly fractured, and depleted zones. For example, in
the case of depleted zones or reservoirs, as the reserves decfine
the pore pressure decreases resulting in weakened hydrocarbonbearing
rocks. While the nearby or inter-bedded J-ow permeabiJ-ity
rocks try to maintain their pore pressure, the situation can
however make the drilling of such depleted zones extremely
diff,icult. Thus, 'to address the lost circulation problem in
hiqhly permeable, hiqhly fractured, and depletëd zones a large
capital expenditure and time is required. These additional
expenses and time in turn lead to an increased overall
operational expense.
t 000s l Over the years/ numerous sol-utions have been used to
restore circulation of the drifling fluid when a lost circufat-ion
event has occurred. ParticularJ-y, use of traditional Lost
Circul-ation Materials (LCM) that seal or btock further loss of
circufation flui-d is welf known. These solutions or materials
are generally classified into several categories like surface
plugging, interstitial bridging, and/or combinations thereof. fn
addition to these existing solutions, traditlonal LCM pilJ-s,
crosslinkable or absorbing polymers, and cement or gunk squeezes
have al-so been considered. However, each of these known in the
art sol-utions have one or more limitations.
t00061 Accordingly, there exists a continuing need for
development for new LCM treatments that may be used during the
lost circuÌation event so that circulation may be more readily
resumed without spendlng a large amount of money and time.
SUM}ÍARY OE' THE TN\TENTION
t00071 In an embodiment of the present invention, a
composition for a Lost Circulation Control- (LCC) piJ-l 1s
provided. The composition for the LCC pill comprises water in a
range from 60å to 100å by volume of the LCC pltl, a deformet in
a range from 0.2å to 0.5å volume/volume of water, boric acid in
a range of 3å to 15% weight/volume of water, XC Polymer in a
range of 0 .252 to 0.5å weight/volume of water, magnesium sulfate
in a range of 60å to 100å weight/volume of water, Dead Burnt
Magnesite (DBM) in a range of 40å Lo I20å weight/volume of water,
and wollastonite in a range of 10å to 20% weight/vofume of water.
Further, the set time of the LCC pì-Il ranges from 90 minutes to
110 minutes at Bottom Hole Circulating Temperature (BHCT) in a
range of 60'C to 105'C.
t000Bl The LCC pill maintains an initial consistency of 10
Bearden units of consistency (Bc) for up to 85 minutes prior to
displaying a right angle set behavior. At 70"C, the LCC pill
maintains an initial consistency of 10 Bc for up to 95 minutes
before displaying a right angle set behavior.
t00091 Further, when the LCC pill is unconditioned,
thì-ckening time of the LCC píll ranges from 280 minutes to 84
minutes for BHCT in a range of 45"C to 105"C. When the LCC pitl
is conditioned, the thickening time of the LCC pill ranges from
280 minutes to 100 mínutes for BHCT in a range of 45"C to 105'C.
[0010] Furthermore, the LCC pill achieves a compressive
strength of 200 per sqì;are inch (psi) to 300 psi in 5 to 6 hours.
Also, the LCC pill takes 75 minutes to 135 minutes to dissol-ve
completely in 153 vofume/volume HydrochJ-oric acid (HCL) acid at
45'C. The particle size of the LCC pill is in a range of 5-10
microns .
BRIEF DESCRIPTION OF THE ACCOMPA}TYING DR;AWTNGS
100111 The present invention is described by \day of
embodiments il-lustrated in thc accompanying drawings wherein:
t00121
preparing and testing
Circulation Control (LCC)
of the present invention;
[0013] FIG. 2 shows test results for a
viscosity curve at 60'C for an LCC pill
embodiment of the present invention;
t00141 FIG. 3 shows test results for a
viscosity curve at 70"C for an LCC pitt
embodiment of the present invention;
FIG. 1 is A
i00151 FIG. 4 is a graph
strength of the LCC pill in
present invention;
flowchart ilfustrating a process for
one or more compositions of Lost
pilts in accordance with an embodiment
typical temperature vs
in accordance with an
t.ypical temperature vs
in accordance with an
illustrating a
accordance with
test for compressive
an embodiment of the
100161 Frc.
pill cubes in
embodiment of
5 is a graph illustrating
Hydrochloric acid (HCL)
the present invention;
dissolution of the LCC
in accordance with an
t00171 FrG.
LCC pills in
ínvention,' and
t 0018 I FrG.
more LCC pills
invention.
6 ill-ustrates a first field trial- of one or more
accordance with an embodiment of the present
7 íllustrates a second field trial of the one or
in accordance with an embodiment of the present
DETATLED DESCRTPTION OF THE TN\ZENTION
t00191 The present invention provides one or more
compositions of a Lost Circulation Control (LCC) pill for curing
fost circufation in oil and gas reservoirs. The LCC pilt is a
stoichiometric mixture of magnesium compounds that form a series
of high molecular weight magnesium inorganic poly hydrates. The
LCC pill displays characteristics of a conventionaf cement slurry
in pumpability, yet being chemically different from the
conventional cement slurry. The LCC pill when placed in the l-ost
circulation zone, rapidly transitions from liquid state to solid
state and builds sufficient compressive strength to cure losses
caused due to lost circulalion problem.
t00201 The folJ-owing disclosure is prowided in order to enable
a person having ordinary skilf in the art to practice the
ínvention. Exemplary embodiments are provided only for
illustrative purposes and various modifications will be readily
apparent to persons skilled in the art. The general principles
defined herein may be applied to other embodiments and
applications without departing from the spirit and scope of the
invention. Also, the terminology and phraseology used is for the
purpose of describing exemplary ernbodiments and should not be
considered limiting. Thus, the present invention is to be
accorded the widest scope encompassing numerous alternatives,
modifications and equivaJ-ents consistent with the principles and
features discÌosed. For purpose of clarity, details relating to
technical material that is known in the technical- fields related
to the invention have not been described in detail so as not to
unnecessarily obscure the present invention.
l002ll The present invention would now be discussed in context
of embodiments as illustrated in the accompanying drawings.
t0022) The compositions of the one or more LCC pil1s for
controlling mild to severe lost circul-ation damages is a critical
aspect of the LCC pill as conditions within the oil and gas wells
are extremely harsh. In this regard, the compositions of the one
or more LCC pil1s describecì he::ein have been designed and tested
for an anticipated broad rânge of temperature and pressure
conditions that may occur during drilting operations in oil and
gas wells.
t 0023 l FIG. 1 is a flowchart ilfustrating a process for
preparing and testing one or more LCC pills in accordance with
an embodiment of the present invention. In an embodiment of the
present invention, the one or more LCC pills may be prepared and
tested for curing lost circufation in depleted oil and gas
reservoirs. In another embodiment of the present invention, the
one or more LCC pills may be prepared and tested for producing
and non-producing reservoirs. fn yet another embodiment of the
present invention, the one or more LCC pills may be prepared and
tested for lost circulation occurring during drifling of a wel-l-.
100241 At step 702, the one or more LCC pills are prepared.
fn an embodiment of the present inventíon, various compositions
of one or more LCC pills are prepared and tested for their
appÌicability in controlling the lost circulation in the depleted
oil and gas reservoj-rs. The one or more LCC pì-lÌs are prepared
by mixing a retarder, ân antl-settling agent, magnesium sul-fate
(MgSOa), Dead Burnt Magnesite (DBM), and wollastonite.
t00251 In an exempJ-ary embodiment of the present -inventi.on,
the retarder may be boric acíd. The retarder is used to adjust
setting time of the one or more LCC pills" The concenr-ral:lon of
the retarder is dependent on Bottom Hole Circufatlon Temperature
(BHCT) of the well-bore and concentration of the DBM.
t0 02 61 The anti-settling agent facilitates the one or more
LCC piJls to become a qel structure. In an exemplary embodiment
of the present invention, XC-polymer may be used as the antisettling
agent. The XC polymer exhibits several properties
including, but not limited to, high shear thinning rheology,
good suspending capacity, good thermal stabiJ-ity, good shear
resistance, and an excelfent leak-off rate
10021 l The magnesium sul-fate facifitates solubílity of the
one or more LCC pills in water and is used as a desiccant due to
its strong hygroscopic nature. Tt is the main ingredient of the
LCC pill and reacts with the DBM to form Magnesium Oxy Sul-fate
(MOS), when thermal-ly activated. In an embodiment of the present
invention, as the one or more LCC pills enter the l-ost
circuÌation zone in liquld state, rapid heat transfers from the
welf formation to the one or more LCC pills. This triggers an
exothermic reaction between magnesium sul-fate and magnesium
hydroxide resulting in forrnation of MOS. The MOS sets ínto a
sol
to
id cementitious mass thereby providing a compresslve strength
controf the lost circulation losses.
t002Bl Further, the DBM comprises an active ingredient
Magnesium Oxide (MqO) which causes the one or more LCC píJ_Is to
set and become a cementitious product with sufficient compressíve
strength. In an embodiment of the present invention, in order to
prepare the one or more LCC pilfs the DBM may possess predefined
ph\rsicaf and chemical properties as listed in TABLE 1 and TABLE
2 respectively.
Physical Properties of DBM
Fineness (sieve anal-ysis) retained on
100 BSS mesh
Maximum 5å by mass
Fineness retained on 200 BSS mesh Maximum 202 by mass
Moisture content at 10512"C Maximum 2% by mass
Loss on ignition at 1000'C Maximum 2å by mass
TABLE 1
l002el
TABLE 2
Further, the physica] state of the desired DBM material
may be a fine light brown colored powder which is free from dirt
or any other foreign material. The desired DBM may also be
required to pass a reactivity test. The reactivity test of the
DBM is the time taken by the DBM sample to change from white to
Chemical Properties of DBM
Mgo Maximum 85å by mass
S iOz Maximum 4% by mass
CaO Maximum 4% by mass
FezO: Maximum 5% by mass
pink color in 0.025 M citric acid sol-ution in presence of
phenolphthalein indicator at approximately 25'C. In an
embodiment of the present invention, the DBM sample takes 900
minutes to change from white to pink cofor.
t 00301 Further, the wolÌastonite is used as a fiber material
and improves ffexural and impact strengths of the one or more
LCC pills. Vüollastonite is an industrial mineral comprised
chemicalÌy of calcium, sil-icon and oxygen. Its mol-ecuf ar formula
is CaSiO: and consists of 48.28?; CaO and 5I.J2e" SiOz.
10 031 1 In exemplary embodiments of tlie present invention, the
one or more LCC pills may be prepared using American Petroleum
Institute (API) recommended practices. Further various equipment
may be used to prepare the one or more LCC pilJ-s. The equipment
may incl-ude, without any lirnitation, warj-ng blender I a
pressurized and atmospheric consistometer, an eight speed Fann
viscometer, a pressurized curing chamber, a water bath, a
compressive strength tester, and a magnetic stirrer with hot
plate. It may be apparent to a person of ordinary skill in the
art that all these equipment are known in the art and thus detaifs
of these equipment have not been disclosed in det.ail "
t0032 l Further, in an exemplary embodiment of the present
pitl may be prepared by mixing the ingredients
as listed in Table 3.
invention, the LCC
in the quantitì-es
fng'redient Quantity
Deformer 0.22 to 0.5? vof ume/vol-ume of water
hlater 602 to 100å by volume of the LCC piJ-JXC
Polymer 0.252 to 0.5å weight/volume of water
10
Borlc Acid 3å to 15å weight/volume of water
Magnesium Sulfate 602 to 100å weight/volume of water
Wollastonite 10å to 202 weight/volume of water
Dead Burnt
Magne s i te
402 to I20Z weiqht,/volume of water
TABLE 3
i00331 Furthermore, in a preferred embodiment of
invention, 50 barrel-s of LCC pitl may be prepared by
ingfêdients in the quantities as listed in Table 4.
the present
mixing the
fngredient Quantity
Deformer (Iiters) 10
Water (bbf ) 30
XC Polymer (Kq) LZ. J
Boric Acid (Xq) 150
Magnesium Sulfate (Kq) 3000
Wol-lastonite (Kg) 500
Dead Burnt Magnesíte (Kq) 4000
TABLE 4
t00341 After the one or more LCC pil-ls have been prepared, at
step I04, the one or more LCC pills are tested for their
applicability in curing the lost circufation l-oses. The one or
more LCC pills are tested on different parameters including,
without any limitation, working temperature range, right angle
set behavior, thickening time/ compressive strength, solubility
in acid, and seal-ing ability.
t00351 The one or more LCC pills are tested for different
working' temperatures in a range frorn 60'C to 105'C BHCT by
tI
altering their formulations. Set times for the one or more LCC
pills, which are dependent on temperature and time/ are further
tested for their desj-red accuracy. fn an exemplary embodiment of
the present invention, the desired set time of the one or more
LCC pills ranges from 90-110 minutes with accuracy tol-erance of
three to five minutes. During this setting time range, the one
or more LCC pills remain in a pumpable state which alfows
appropriate placements of the LCC pill in the lost circulation
zone of the depleted reservoirs.
100361 The riOht ¿Jlrrr a cor i-ra1.r:r7i ¡r teSt aSCeftai ns the
exothermic property of thl one or more LCC pi1Is. This test
indicates that the one or more LCC piJ-ls give sufficient time in
transitioning from liquid state to solid state before their
setting process is triggered. FIGS. 2 and 3 show right angle set
behavior test of the LCC pill at 60'C and 70'C in accordance
with different embodiments of the present invention. As it can
be seen from the test results, the LCC pill remains as fow
viscosity fluid with a consistency of around 10 Bearden units of
consistency (Bc) during its placement. This consistency remains
maintained for close to 85 minutes in FIG. 2 and 95 minutes in
FIG. 3. Beyond this time, the transition of the LCC pill from
fluid state to sofid state is instant resulting in zero gas
migration or channeJ-ing. It may be apparent to a person of
ordinary skill in the art that this sudden transition is known
as right angle set behavior. The right angle set behavior occurs
as the LCC pill is an exothermic material. Further, as the LCC
pill reaches the l-ost circulation area it starts spreading out.
Because of this spreading and temperature transfer, the
exothermic reaction of the LCC pill qets exponentially
accelerated. This condition triggers the setting process of the
L2
LCC pill before it penetrates
faciÌitates curing of the fosses
into the formatíon and thus
in the Ìost circulation zones -
t 0037 l The thickening time of one or more LCC pills is
analyzed to determine the time required to prepare and place the
one or more LCC pills in the l-ost circulation zones " In an
embodiment of the present invention, thickening time is the time
elapsed from the initial application of temperature and pressure
to the time required for the LCC pi.ll to reach a consistency of
100 Bc. The thickening li*" i" a function'of temperature, the
type of ingred:-ents used, and- is determined at BHCT conditions.
The thickening time of the one or more LCC pills may be cafculated
or tested using High-Pressure, High-Temperature (HPHT)
consistometer. In an embodiment of the present invention, the
thickening time of the one or more LCC pills is determined
wi[hout conditioning the one or more LCC pills as per API
Recommended Practices. In another embodiment of the present
invention, the thickening time of the one or more LCC pills is
determined after conditioning the one or more LCC pil1s as per
API Recommended Practices.
t003Bl TABLE 5 shows readings for the thickening time tests
carried out for the one or more LCC pills, without conditioning,
from 45"C to 105"C BHCT. It may be apparent to a person of
ordinary skill in the art that thickening time without
conditioning refers to the thickening time of LCC pitls
determined directly after the LCC piÌl is prepared, poured in a
slurry cup, placed in pressurized consistometer and subjected to
BHCT raised in 30 minutes from ambient conditi-ons.
13
Temperature
0c
MgSOa
3 BTfOTf,
DBM
% BWOI{
Boric Acid
% BT{OVí
Thíckening
Time
(minutes)
45 r00 I20 280
60 100 I20 130
15 60 BO 1 I40
90 60 BO 2 100
90 60 BO 3 130
105 60 BO 6 B4
105 60 BO B 726
TABLE 5
t00391 TABLE 6 shows readings for the thickening time tests
carried out for LCC pilts after conditioning. In an embodiment
of the present invention, the one or more LCC pills after their
preparation are conditioned in atmospheric consistometer at 45'C
for one hour and then the thickening tíme for these LCC pills is
determined.
Ternperature
0C
MgSOa
% BWOW
DBM
% BWOW
Boric Acíd
% BWOW
Ttrickening
Time
(minutes)
45 100 120 280
60 100 120 120
15 60 BO I 130
90 60 BO 2 100
90 60 BO 3 126
L4
105 60 BO B 720
TABLE 6
t00401 fn an embodiment of the present inventíon, the
compressive strength of the one or more LCC pills is tested by
preparing one or more molds. For tests, the molds are cured at
60"C and at atmospheric pressure for six hours. The molds are
then tested using known in the art compressive strength testinq
methods. FIG. 4 is a graph iflustrating a test for compressive
strength of the LCC pill in accordance with an embodiment of the
present invention. The test results indícate that the LCC pill
develops an anticipated compressive strenqth i.e., in the range
of 200-300 psi. The test result further illustrates that the
compressive strength continues to remain at around 270 psi for
around 78 hours at a pressure of 2000 psi and at 105'C BHCT. At
this compressive strength range the one or more LCC pills are
sufficient enougrh to control the static and dynamic fost
circulation losses. In exemplary embodíments of the present
invention, the drill-íng fluid that gets fost in the formation
when the drilting fl-uid is not in circufation is considered as
static loss. Eurther, the drilling fluid that gets lost in the
formation when the drilling fluíd is in circulat.ion is considered
as dynamic foss.
[0041] In an embodiment of the present invention, the
solubility of the one or more LCC pitls in acid is tested by
studying behavior of I" LCC pill cubes in 15å vol-ume/volume
Hydrochloric acid (HCL) acid at 45'C. FIG. 5 is a graph
iffustrating dissolution of the LCC pill cubes in HCL in
accordance with an embodiment of the present invention. As shown
15
in the graph, the LCC píll cube material takes 75 minutes to 135
minutes to completeJ-y dissofve in HCL. The graphs I,2,3, and
4 indícate dissol-utíon of the LCC pill cube at Room Temperature
(RT) and at 45'C wlth and without Mícronized Calcium Carbonate
(MCC) . The results al-so indicate that the rate of acid solubility
increases with either use of MCC content or by increasing the
temperature for a given piJ-J- design. The increase in sofubility
of the LCC pill material in HCL with increase in MCC suggests
that MCC is al-so non-damaging to the formati ons and further
improves bridging efficiency of the one or rnore LCC pills.
100 421 The sealing ability of the one or more LCC pilfs is
tested us-ing known j-n the art techniques. The test resuÌts
indicate that during pumpabiJ-ity the one or more LCC pills
display characteristics of a conventionaf cement slurry. The
stoichiometric mixture of magnesium compounds form a series of
high mol-ecul-ar weight magnesium inorganic poly hydrates that
gives LCC pills characteristics of a conventionaf cement slurry.
In an embodiment of the present invention, the one or more LCC
pills set rapidly and attain desired compressive strength within
5-6 hours. Eurther, the reaction causing sealing or
solidification of the one or more LCC pilts is a function of
time and temperature and is unaffected by hydrostatic pressure.
t00431 The present invention further comprises conducting
fleld trials of the one or more LCC pills that have been prepared
and tested. FIG. 6 illustrates a first field trial of the one or
more LCC pills in accordance with an embodiment of the present
invention. The ob;ective of the first field trial is to Lest the
one or more LCC pills in moderate lost circulation conditions.
As depicted in FIG. 6, the field trial is conducted in an oilreservoir
with 1050 meter horizontal drift in 50o north for oil
1.6
expl-oitation from lower layers. A
at IB14 meter and a 6 inch drain
meter) of 266 meter is drilled.
drain, a dynamic loss at 1935-40
Barrels per Hour (BPH), which
achieving a target depth of 2740
seven inch liner shoe rs seated
hole ( from IBl 4 meter to 2140
Vühile drilling the 6 inch hofe
meters is experienced at 50-60
reduces to 35-40 BPH while
meters .
100441 In an exempJ-ary embodiment of the present invention,
two LCC pills, a first LCC pitl of 25 barrel-s and a second LCC
pitl of 45 barrels, are placed into the affected or lost zones
of the well " Tn emboCinent-s of the present in-zentio:-r, pl acem.ent
of the LCC pills in the we.ll may be achieved using techniques
tike, without any limitation, balanced pfug placement method and
bullheading placement method. The pLacement of the LCC pills 1s
dependent upon the formulation/composition and volume of the LCC
pilJ-. The placement is further dependent upon well bore
temperature, well condition and wefl behavior i.e. loss zonel
loss rate and length to be covered. Further, in an embodiment of
the present invention, the particle size of the LCC piJ-l- material
is 5-10 microns. This particle size makes the LCC pill suitable
for pumping through any drilling assembl-y without blocking any
nozzLes or apertures in the Bottom Hole Assembly (BHA)
t004sl Further, viscous spacer as pre-flush and after-flush
are also pumped ahead and after the two LCC pills. The two pills
are displaced with 8.5 pounds-per-gallon (ppq) Non Damaging
Drilling Fluid (NDDF) mud. Thereafter, appropriate time is given
to the LCC pills to form gels. The LCC pills are then made to
enter into the l-ost circufation zone by applying a pressure in
t.he range of 200-300 psi after reverse circulation. After 5-6
hours a resistance is observed due to sol-idification of the LCC
pills from 1913 meters to I915 meters. This resistance gives an
tl
indication of the curing of the lost circulation l-osses in the
lost circulation zone. Finally, after the first field trial is
complete the set LCC pills are washed away without any losses
and hoÌe deviation. In an exemplary embodiment of the present
invention, TABLE 7 shows the field trial results.
TABLE '7
t00461 Based on the test results in TABTE J, it may be
apparent to a person of ordinary skill in the art that the LCC
pills managed to reduce dynamic losses from 40 BPH to 20 BPH
thus, achieving a success ratio of 50å. Further, the static
losses r^rere reduced to 3 BPH from a staggering 30 BPH and thus,
achieving a success ratio of 9OZ.
t00471 FIG. 7 ilfustrates a second field trial of the one or
more LCC pills in accordance with an embodiment of the present
invention. The objective of the second field trial is to test
the one or more LCC pills in high to Lotal lost circulation
conditions. As depicted in FIG. 6, for the second field trial a
fimestone formation in I21a inches section is drilled from 128
meters Lo 1525 meters with gel-polymer mud of 8.6-8.9 ppg. Then,
a changeover is drilled in another section up to 1800 meters. fn
this process, two l-oss zones are encountered at 780 meters and
BB0 meters. fn these Ioss zones, the dynamic l-oss is
approximately 150 BPH and the static loss is approximateJ-y I20
Losses Dynamic Loss (BPH) Static Loss (BPH)
Be fore 40 30
After 20 3
Success Ratio (%) 50 90
18
BPH. In an embodiment of the present ínvention, two LCC pills of
50 barrels each are pJ-aced using balance plug method to cure the
loss zones encountered at 780 meter (first foss zone) and BB0
meter (second loss zone). A first LCC pi-ll which is used to cure
the loss zone at 780 meters is placed using a 5a¿ inches Open
Ended Drill Pipe (OEDP) at 750 meters i.e. at top of the first
loss zone. A second LCC pill which is used to cure the loss zone
at BBO meters is placed through a I2L< inches buitdup assembly at
850 meters. Cnce the two LCC piJ-J-s have l:een placed, af ter
waiting on piJ-l for 5-6 hours, the dynamj-c'and static losses in
the loss zones I¡/ere surpr.i singll' reCuced tc ni1. Further, after
the second field triaf is complete the set LCC pills are washed
ah/ay without any losses and hole deviatiofl; Iû an exemplary
embodiment of the present invention, TABLE B shows the .results
for the field trial.
TABLE B
l004Bl Based on the test resul-ts in TABLE B, 1t may be
the art that the LCC
150 BPH to absol-utely
of 100%. Further, the
a I20 BPH and thus,
apparent to a person of ordinary skill in
pills managed to reduce dynamic losses from
nil losses thus, achieving a success ratio
static losses \^/ere reduced to ni1 from
achieving a success ratio of 1003.
Losses Dynamic Loss (BPH) Static Loss (BPH)
Before 150 720
After NiI Nif
Success Ratio (å) 100 100
L9
l004el Thus, based on various tests conducted on the LCC pills
and also field trials of the LCC pills, it may be apparent to a
person of ordinary skill in the art that the one or more
compositions of the LCC pifJ-s of the present inventlon provide
an effective sol-ution to mítigate severe dynamic and static
circufation losses in the depleted reservoirs. The LCC pills
also demonstrate surprising and unexpected results in both
producing and non-producing reservoir zones. Further, the one or
more compositions of the LCC p111s can be prepared from
indigenously available chemicals and materials. Thus, the one or
more compositlons of 't-he LCC pi1ls provicle u ¡¡ i quer easy/
effective and a cost benefit soÌution over the tradrtionally
known and available lost control sol-utions.
t00501 Whlfe the present invention has been shown and
described with reference to preferrecl embodiment-s, it will be
understood by those skilled in the art that various changes in
form and detail may be made therein without departing from or
offending the spirit and scope of the invention as defined by
the appended claims.

We Claim:
1. A composition for a Lost Circulation Control (LCC) pitl, the
composition compris ing :
water in a range of 60å to 100å by volume of the LCC pill;
a deformer, wherein the deformer ranges from 0.22 to 0.5%
volume/vofume of water,'
boric acid in a range of 3% to 15U weíght/vofume of water,'
XC PoJ-ymer in a range of 0.25e. to 0.5? weight/volume of
water;
magnesium sul-fate in a range of 602 to 1003 weight/volume
of water,'
Dead Burnt Magnesite" (DBM) in a range of 402 to I20Z
weight/volume of wateri and
wollastonite in a range of 10? to 202 weight/volume of
water;
2. The composition as cfaimed in claim I, wherein the LCC pilf
achieves a success rate of 50å in curing dynamic loss and a
success rate of 90å in curing static loss in moderate l-ost
circufation conditions.
3. The composition as cl-aimed in claim 7, wherein the LCC pill
achieves a success rate of 100å j-n curing dynamic loss and
static Ìoss in high lost circuÌation conditions.
4. The composition as claj-ned in claim 1, wherein set time of the
LCC pill ranges from 90 minutes to 110 mlnutes at Bottom Hole
Circulating Temperature (BHCT) in a range of 60'C to 105'C.
5. The composition as claimed in claim I, wherein at 60'C, the
LCC pil1 maintalns an initial consistency of 10 Bearden units
2t
of consistency
a right angle
(Bc) for up to B5
set behavior.
The composítion as claimed in
LCC pill maintains an initial
95 minutes prior to displaying
minutes prior to displaying
claim 7 , wherein at '7 0" C, the
consistency of 10 Bc for up to
a right angJ-e set behavior.
The composition as claimed in claim 1, wherein thickening time
of the LCC pilt ranges from 280 minutes to 84 m:rnutes for BHCT
in a range of 45'C to 105'C, further wherein the LCC pill is
unconditioned.
The composition as claimed in claim 1, wherein thickening time
of the LCC pill ranges from 280 minutes to 100 minutes for
BHCT in a range of 45oC to 105'C, further wherein the LCC pill
is conditioned"
The composition as claimed in cfaim I, wherein compresstve
strength of the LCC pill is in a range of 200 per square inch
(psi) to 300 psi in 5 to 6 hours.
10. The composition as claimed ì-n claim 1, wherein the LCC pill
takes 75 minutes to 135 minutes to dissol-ve completely in 15?
volume/vol-ume Hydrochloric acid (HCL) acid at 45 "C.
11. The composition as claimed in claim 7-, wherein particle
síze of the LCC pilÌ is in a range of 5-10 microns.
. The composition as cl-aimed in claim I, wherein physical
properties of the DBM comprise: fíneness retained on 100 BSS
mesh - maximum 53 by mass, fineness retained on 200 BSS mesh
- maximum 5% by mass, moisture content in a range of 103'C
12
22
107"C - maximum 22 by
maximum 2å by mass.
13. The composition as
comprises a maximum B5å
maximum 2å by mass CaO,
mass, loss on ignitlon at 1000'C
claimed in claim I, wherein the DBM
by mass MgO, maximum 4Z by mass SiO2,
and maximum 53 by mass Fe2O3.