Positive Reactions in Carbonate

7/30/2019 Positive Reactions in Carbonate

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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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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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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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The stimulation fluid must be properly placed in theselected intervals Downhole through the casing orcoiled tubing

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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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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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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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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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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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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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Produced hydrocarbon Transforming them into

spherical micelles lower viscosity, facilitating complete

break and efficient cleanup.

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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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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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This process continues until all perforated zones of varying

permeability are stimulated

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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 temperatures 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 openhole-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

Positive Reactions in Carbonate

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