Well Stimulation _ Hydraulic Fracturing

G

R

O

U

P

Production Enhancement

(Matrix Stimulation and Hydraulic Fracturing) Alberto Casero

Eni Corporate University – Eni E&P Division

Junior Production Engineering/Stimulation Rev. 00 - Jan. 05/EP Page 1 of 41

Eni – E&P Division

Well Stimulation Eni Corporate University – Eni E&P Division


Production Enhancement

REMOVE DAMAGE

MAX PRODUCTIVITY



FORMATION DAMAGE

•Filter cake

•Formation



FORMATION DAMAGE HOLE Formation

FRACTURE Filter Cake Zone invaded by mud spurt Formation

Bridging Zone



PERFORATIONS

#2 A downside perforation #4 A topside perforation Multiple Perforations in Sandstone block



Production Enhancement in Limestone Formation type

Main treatment technique

i Good K ii

Medium K or Low K with existed micro fractures

iii Low K

CT Jetting HCl

With the help of Pulsonix® Hydra Blast Pro® Gelled HCl

CT Spotting+ Bullheading Gelled HCl using MAPDIR StimGun® – StimStick®

Acid Gelled Frac with Closure Fracture Acidizing

Mechanical barrier in CH SurgiFrac in OH

iv Very Low K and closure stress problem

Proppant Frac


Proppant bridge Mechanical barrier Junior Production Engineering/Stimulation Rev. 00 - Jan. 05/EP Page 7 of 41

PURPOSE OF MATRIX STIMULATION

To remove formation damage from the ENTIRE producing sections of Vertical Wells & Horizontal Wells



TRADITIONAL APPROACH

PROBLEM : Fluid naturally tend to follow the path of least resistance (higher permeability / undamaged zones )

SOLUTION : Effective diversion methods



UNIFYING CONCEPT FOR DIVERSION TECHNIQUES

To be effective , any Diversion Technique must be able to provide sustained , planned Dp levels during matrix stimulation



UNIFYING CONCEPT FOR DIVERSION TECHNIQUES Darcy’s equation shows how different diversion techniques help maximize ∆p in radial flow conditions :

141.2 qi µw ∆p = Kwh

[ ( ) ] In

Mechanical Isolation z Ball Sealers z Chemical ( Particulate ) Diverters z Viscosified Fluids , Foams z

z

New Diversion Technique


rb rw

+s

(1)

Reduction of h (Kh) Reduction of h (Kh) Increase of s Increase of µ

Increase of qi


MAXIMIZED PRESSURE DIFFERENTIAL INJECTION RATES ( MAPDIR ) TECHNIQUE

Injection rate is the key for sustained , planned Dp levels Stimulation fluids must be placed downhole so as to cover the total interval to be treated Applicable wherever Darcy’s law holds z Sandstones z Poorly consolidated sands z Unfractured or microfractured limestones / dolomites



MAPDIR TECHNIQUE GUIDELINES FOR FIELD APPLICATION 1) Set ∆pmax in matrix conditions

z

z

∆pmax = 0.8 ∆pf = 0.8 ( pf - pe ) pf = 2

(

ν 1- ν

) (p

o

)

- pp + pp



MAPDIR TECHNIQUE GUIDELINES FOR FIELD APPLICATION

2) Select qimax stimulation rates

qimax

0.00708 Kwh = ∆pmax rb µw In rw + s

[ ( ) ]



MAPDIR TECHNIQUE OVER A 100ft INTERVAL



MAPDIR TECHNIQUE STIMULATION RATE SCHEDULE



FIELD - ACID - RESPONSE CURVES FOR SANDSTONES



MAPDIR TECHNIQUE

FIELD ACID RESPONSE OF SEVERAL SANDSTONE RESERVOIR



FIELD - ACID - RESPONSE CURVES FOR LIMESTONES



FIELD EXPERIENCE

The MAPDIR technique has been applied to 1200+ matrixstimulation treatments

Key factor for success rate : > 85 %

Multilayered sandstone reservoirs as thick as 300+ ft successfully stimulated ( without diverting agents )

MAPDIR an effective stimulation technique for horizontal well and drain hole



MATRIX STIMULATION DESIGN WELLHEAD PARAMETERS



FRICTION LOSS REDUCTION FOR ACID MIXTURE



SUMMARY OF ANALYZED HORIZONTAL DRAIN - HOLE WELLS WELL

TURNING RADIUS

HOLE SIZE (inches)

COMPLETION

OPEN LENGHT (feet)

MATRIX STIMULATION

C.E. (%)

H1 H2 H3

MEDIUM SHORT LONG

6 1/2 6 8 1/2

OPEN HOLE OPEN HOLE 5” SLOTTED LINER

1460 564 650

H4 H5 H6 H7 H8 DH1 DH2 DH3 DH4

LONG LONG LONG LONG LONG SHORT SHORT SHORT SHORT

8 8 8 8 8 5 5 5 6

5” SLOTTED LINER 7” CEMENTED 7” CEMENTED 7” CEMENTED 7” CEMENTED OPEN HOLE OPEN HOLE OPEN HOLE OPEN HOLE

815 720 846 920 510 470 314 626 380

CT + BH TP + BH CT + BH ( 13 bbl / min ) CT + BH ( 30 bbl / min ) CT CT CT + BH CT + BH CT TP + BH TP + BH CT + BH CT + BH

70 --35 75 --60 84 95 -----------

1/2 1/2 1/2 1/2 1/2 7/8 7/8 7/8

CT = Spotting acid mixture with coiled tubing BH = Bullheading phase


TP = Spotting acid mixture with tail pipe C.E.. = Completion efficiency


FIELD EXPERIENCE

SUCCESS IS RELATED TO THE MAXIMUM INJECTION RATE

H3

LONG

8 1/2

5” SLOTTED LINER

650

CT + BH ( 13 bbl / min )

35

CT + BH ( 30 bbl / min )

75

H5

LONG

8 1/2

7” CEMENTED

720

CT

60

H6

LONG

8 1/2

7” CEMENTED

846

CT + BH

84

H7

LONG

8 1/2

7” CEMENTED

920

CT + BH

95



DEPENDENCE COMPLETION EFFICIENCY ON SPECIFIC INJECTION RATE



WELL H7 EXPERIENCE

H7 H7

LONG LONG

88 1/2 1/2

7” 7” CEMENTED CEMENTED

920 920

CT CT ++ BH BH

95 95

Stimulation job steps :

Spotting HCI 28 % ( 15 gal / Ft ) with coiled tubing Bullheading phase with HCI 28 % ( 30 gal / Ft )

Maximum injection rate : 52 bbl / min



WELL H7

MATRIX STIMULATION PRESSURE - RATE CHART



WELL H7

EVALUATION OF MATRIX STIMULATION



WELL H2 EXPERIENCE H2 H2

SHORT SHORT

66

OPEN OPEN HOLE HOLE

564 564

TP TP ++ BH BH

-----

Stimulation job steps :

Spotting acid mixture with tail pipe Bullheading phase : 6000 gal 28 % HCL 3000 gal 28 % viscosified HCI 2000 gal 28 % HCI 2000 gal 28 % viscosified HCI 4000 gal 28 % HCI

Maximum injection rate : 56 bpm ( Equivalent rate at µw = 1 cp ) Eni Corporate University – Eni E&P Division


WELL H2

MATRIX STIMULATION PRESSURE - RATE CHART



WELL H2

EVALUATION OF MATRIX STIMULATION



WELL H2

SKIN FACTOR vs INJECTED ACID MIXTURE VOLUME



CONCLUSIONS

Effective diversion is obtained by using injection rate as the key to maximized ∆p during matrix stimulation

Fluids must be placed down hole so as to cover entirely the interval to be stimulated

The MAPDIR technique : z

Is very simple to use ; cheap and low risky

z

Is applicable to both cased and open holes

z

Favourably replaces diverting agents

z

Allows real-time evaluation and fast decision

z

Allows field stimulation response evaluation



STIMULATION TECHNIQUES HYDRABLAST This CT-run tool is effective in cleaning out tubulars and perfs: • Fluid jet technology from downward and side nozzles • Low rotating speed to allow for enough time for jetting action to remove damage/deposits



STIMULATION TECHNIQUES PULSONIX Effective for near wellbore and perforation damage: • Fluidic oscillator: no moving parts (lower chance of failure) • Pulsating pressure waves are generated that break damage/deposits by fatigue



STIMULATION TECHNIQUES STIMGUN-STIMSTICK These tools combine conventional guns with perforation frac capability: • High pressure CO2 is produced upon gun detonation • The gas enters the perfs and small fractures are generated

• Can be used in combination with extreme under or over-balance

• Can be used to favor frac initiation



STIMULATION TECHNIQUES SURGIFRAC To create multiple fractures in openhole sections: • Combines annular and tubing flow • High P fluid jet from tbg creates a cavity which initiates a frac • Annular fluid is drawn into the frac extending it

• DP or CT conveyed tool • Suitable for prop and acid fracturing



STIMULATION TECHNIQUES ACID FRACTURING

Guidelines: • Target intervals 60-70 m high • Typical volumes: 30 m3 pad + 30 m3 acid (gelled HCl 15%) • Perform closed-fracture acidizing • Short perf interval Expected results: • 30-35 m half length • Production FOI: • 1.3 for one frac • 2.3 for four fracs


Half length Up growth Down growth Width


INTELLIGENT COMPLETIONS Selective interval production

No effective fluids placed during stimulation

•ANTICIPATE HYDROCARBON PRODUCTION

•REDUCTION OF FORMATION DAMAGE ?

•SHUTOFF UNDESIDERATE FLUIDS

•FUTURE NEW STIMULATION TECHNIQUES ?



DRILLING AND COMPLETION FLUIDS Reduce the solid and filtrate invation into producing zones – Environmentally friendly oil mud (LAO) – Drill-in fluids (DIF) – Clean brine during perforation and completion Please, – monitor pore pressure development-minimize the overbalance – Properly use shale shaker and cyclone – Clean tanks and equipment – When necessary waste the old dirty fluids and input new one



STIMULATION PERFORMANCE

Well Umoru N° 3 Well Performance WHP vs. Flow rate Back pressure equation

250

FTHP

(Kg/cm²)

200

150

After stimulation 100

50 Before Stimulation

Initial IPR

0 200

400 Flow rate (STm³/d) 600


800

1 000


Well Stimulation _ Hydraulic Fracturing

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