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PRESENTED BY:
JULIAN GUILLERMO CARREROARTUR SEBASTIAN FRANCO
JOHAN DARIO CAICEDO
POSITIVE REACTIONS INCARBONATE RESERVOIR
STIMULATION
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CARBONATE RESERVOIR STIMULATION
INTRODUCTION
Carbonate reservoirs About 60% of the worlds oilreserves Huge gas reserves.
The oil trapped in C. reservoirs
Heavy Oil
Notaccessible Economic and technological barriers.
Are stimulated using acid HCl (hydrochloric acid)Create conductive pathways
The Goal stimulated
Effectively treat productivezones Reducing formation skin and improvingproductivity or injectivity.
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CARBONATE RESERVOIR STIMULATION
ACIDIZING IS NOT BASIC
Acid stimulation in carbonate rocks reaction ofhydrochloric acid with the minerals calcite and dolomite[CaCO3 and CaMg(CO
3
)2
]
3 + 2 + + (3) + 4 + + + When the acid is introduced CaCO3 dissolves
creating small conductive channels (wormholes)
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CARBONATE RESERVOIR STIMULATION
ACIDIZING IS NOT BASIC
Conductive wormholesMatrix treatments require lowinjection rates pure HCl cannot
be used rapid acid spendingseverely limits the acid penetrationdistance fails to create awormhole network long enough
Retardation Emulsification and
formation of gels Creates deeperwormholes and the emulsion lesscorrosive.
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CARBONATE RESERVOIR STIMULATION
ACIDIZING IS NOT BASIC
The stimulation fluid must be properly placed in theselected intervals Downhole through the casing orcoiled tubing
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CARBONATE RESERVOIR STIMULATION
ACIDIZING IS NOT BASIC
Mechanical-diversion techniques use of ball sealers orcoiled tubing with straddle packers Not very effectivein the stimulation of long horizontal and extended reachwells.
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CARBONATE RESERVOIR STIMULATION
ACIDIZING IS NOT BASIC
Chemical-diversion methods nitrogen foam, bridgingagents like benzoic acid flakes and crosslinked polymergels Polymer-base gels use reversible pH for alter the viscosity have several drawbacks Have shown that obstructwormholes and could damage the formation.
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CARBONATE RESERVOIR STIMULATION
A UNIQUE FLUID EMERGES Due the damaging effects of polymer-base stimulation
fluids Schlumberger Product Center to explore theuse of VES (viscoelastic surfactants) ClearFRACpolymer-free fracturing fluids
Schlumberger applied VES chemistry to produce apolymer-free acid called the VDA (Viscoelastic DivertingAcid) system maintains a low viscosity.
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CARBONATE RESERVOIR STIMULATION
A UNIQUE FLUID EMERGES
The acid is consumed through the reaction with the calcite
or dolomite the surfactant gels in the form of
monomers
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CARBONATE RESERVOIR STIMULATION
A UNIQUE FLUID EMERGES
Spend acid form long structures called micelles
Dissolution of CaCO3 in HCl results in the formation of
CaCl2 brine creating long worm-like micelles
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CARBONATE RESERVOIR STIMULATION
A UNIQUE FLUID EMERGES
The increased viscosity of the gel reduces flow
Wormholes and fissures within the treated zones
providing effective in-situ acid diversion to unstimulated
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CARBONATE RESERVOIR STIMULATION
A UNIQUE FLUID EMERGES
Produced hydrocarbon Transforming them into
spherical micelles lower viscosity, facilitating complete
break and efficient cleanup.
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CARBONATE RESERVOIR STIMULATION
Stimulation with in-situ diversion
The VDA fluid mixed with acid maintains a low viscosity
Enters the most permeable zone first.
The acid begins to react in the reservoir rock The VESincreases in viscosity
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CARBONATE RESERVOIR STIMULATION
Stimulation with in-situ diversion
The higher viscosity causes new fluid to divert to the next most-
permeable zone The acid stimulates and the surfactant
diverts into the next permeable zone.
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CARBONATE RESERVOIR STIMULATION
Stimulation with in-situ diversion
This process continues until all perforated zones of varying
permeability are stimulated
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CARBONATE RESERVOIR STIMULATION
Stimulation with in-situ diversion
Upon flowback of hydrocarbons, the viscoelastic surfactant
changes its rheology again the long micelles become
spherical micelles the viscosity decreases, allowingcomplete cleanup during flowback.
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DIVERSION IN KUWAIT
Kuwait Oil Company (KOC)
The new VDA system was first used in Kuwait
The carbonate reservoir range permeability
went from 3 to 600 mD
Reservoir pressure averages 2500 psi [17.2
MPa] and typical well tempera- tures reach
170 to 180F [77 to 82C]
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RESULTS OF PLT IN WELL 5
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OTHERS CASES IN KUWAIT
Wells 11, 12 and 13 (which produce heavier oil)
it is pumped down coiled tubing, because the friction, allowing higher pumping rates. After the VDA
treatments, all three wells began flowing naturally
Wells 7
was identified as a stimulation candidate well because it had upper zone with extremely highpermeability and multiple lower zones of lower permeability that had not been stimulated in the past
because of a lack of acid diversion
Production increased dramatically, from 300 BOPD [48 m3/d] with a water cut of 11% before the VDA
treatment to 1300 BOPD [207 m3/d] with a water cut of 15% two months after VDA stimulation
Well 14 and Well 17 (Two HPHT)
Well 13
contained a 2000-ft horizontal open- hole-completion interval and was flowing 1037 BOPD, nly two
stages were required to reach the desired productivity, production increase to 3800 BOPD.
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A SUMMARY OF SAUDI SUCCESSES
Horizontal wells with
openhole horizontal sections
( VES alternatives in 2001)
The use of nitrogen
accelerated cleanup and
minimized acid leakoff,
provided better coverage and
reduced acid- volume
requirements.
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ACID FRACTURING IN SAUDI ARABIA
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Vertical HPHT gas wells
Porosity: natural fracture.
The high temperatures: greatly increase
acid reactivity
high-temperature: the acid is more
corrosive
The combination of Crossslinked gel,
emulsified acid, VDA fluid and a mutual
solvent has proved to be an effective
treatment
ACID FRACTURING IN SAUDI ARABIA
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ACID FRACTURING IN MEXICO
Location of the Matapionche and Mecayucan
fields, Veracruz basin, Mexico 06/05/2013
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PEMEX has employed acid fracturing
Increased gas production
attempts to divert treatments using ball sealers and tocontrol leakoff using gelled oil-base pads were
frequently unsuccessful
The effects of polymers use of VES technology .
The ClearFRAC fluid and the new VDA system
provides PEMEX.
ACID FRACTURING IN MEXICO
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FRACTURING TREATMENTS
USE THREE FLUIDS AND THE STEPS
First: A viscous nonacid ClearFRAC pad initiates the
hydraulic fracture and creates fracture.
Second: An alcohol-acid wiht HCl concentration createwormholes lead to the loss of fluid.
Third: A VDA fluid stage is pumped to fill the worm-holes
establishedWormholes the next volume of alcohol-acid is diverted
to new zones.
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BUILDUP-TEST ANALYSIS FROM
MATAPIONCHE WELL
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NODAL ANALYSIS ON MATAPIONCHE WELL
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MATAPIONCHE WELL TREATMENT PLOT
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A POSTFRACTURE GAMMA RAY LOG
SURVEY ON MATAPIONCHE WELL
The VDA system
has proved highly
effective for
diversion in the
Veracruz basin
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The enormous success of the VDA system is due to the
combination of innovative chemistry, far-reaching technical
support, uncompromising quality control during the design
and operation stages, and the willingness of operators toapply new technology.
This development in carbonate stimulation is making a
clear and positive impact on production and injection rates,
from the smallest wormholes to the largest fields.
THE RIGHT CHEMISTRY
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Please! You don't ask questions.
Thank You!!!31