Preformed Particle Gel (PPG) for Conformance Control

Baojun Baibaib@umr.edu

Petroleum Engineering ProgramUniversity of Missouri, Rolla

(Missouri University of Science and Technology)

Contents

IntroductionPreformed Particle Gel (PPG) Properties

Advantages of PPG over Traditional Bulk Gel

IOR Mechanisms

Application Cases and Lessons

Conclusions

Introduction

What is Preformed Particle Gel (PPG)

(a) Before swelling (b) After swelling

Cross-linked polyacrylamide powder

Introduction

Target for Large Volume Gel Treatments

More and more oilfields are maturing, and excess water production

is the most serious problem to reduce oil production.

Reservoir heterogeneity is a bigger problem as a waterflood

matures -- poorer sweep.

Very low oil saturation near injection wellbore and innerlayer

crossflow require to correct in-depth heterogeneity.

Series of PPG Products

Size Adjustable um-cmSwelling Ratio 30∼200 times original Salt Resistance: All salt type and concentrations

are acceptableTemperature Resistance: High, to 120 ºCLong-term stability: more than 1 years

below 110 ºC.

Advantages of PPG Treatments

PPG treatments more controllable - versusin-situ polymer-gel systems which rely on chemical transport/reactions inside reservoir.PPG is a gel, and so has desirable visco-elastic properties.PPG is a particle, which can selectively enter super-K zones or intervals.PPG quickly well disperses into water (almost any convenient water source).

Advantage of PPG over Traditional Bulk Gel

PPG Bulk Polymer Gel

Chemical reaction Manufactured particle, no in-situ reactions

Affected by interactions with reservoir rocks and fluids

Status in Water Suspension, low viscosity Bulk chemical solution, high viscosity

Temperature Resistance

120 ºC Depend on polymer, usually below 90 ºC

Salinity Resistance

Any salt and concentration Depend on polymer, more sensitive to divalent cationic

Possible damage on formation

Small particle, Selectively enter super-K zones/interval

Like polymer flooding during injection. Gel may form in low permeability zones

Advantage of PPG over Traditional Bulk Gel (Cont.)

PPG Bulk Polymer Gel

Water Any convenient water Usually fresh water requiredPreparation of fluids

Injection SchemeSlug, Alternated injection of PPG/W

Consecutive, Alternated slugs of W/Chemicals not allowed

Costs One composition Polymer+Crosslinker+ Additives

Environmental Friendly (Salty water) Fresh water usually required

Pressure monitoring as an indicator during injection

Quick, good diagnoticto adjust particle size, strength and conc.

Not a diagnostic for gel behavior.

mixing Quickly, well disperse At least 30-60 minutes

Oil Recovery

ER=ED×EA×EV

ER=Recovery Efficiency

ED=Displacement Efficiency Some Effect

EA=Areal Sweep Efficiency

EV=Vertical Sweep Efficiency

IOR Mechanisms of PPG

Biggest Impact –Selective Plugging

Split of Flow (percent)

Oil Recovery ( 98% water cut)

Before (%)

before(%)

7022

after(%)）

91 75549

Total Oil Recovery

No. Permeability

(Darcy) after(%)

Before (%)

After(%)

8.23 20S1

800.5446.8 64.9

Experimental Results of Parallel Core Flooding(Vertical Heterogeneity Model)

Areal Sweep Efficiency Improvement

Before PPG Before PPG InjInj.. After PPG After PPG InjInj..Mainstream

Corner

Injector

Producera. Remaining oil distribution in main stream

b. Oil distribution at corner – Now lower

glass

oil drop

PPGwater

MICROMODEL DEMONSTRATION

More water diverted to corner after PPG injection

Experimental Results from Single Sandpack –Demonstrates Improved Displacement Efficiency

Core No.

K(D)

No1 22.5

20.6No2

PPG Size

(mesh)

Swi(%)

Oil Recovery1

(%)

Oil Recovery2

(%)

Increased Oil Recovery

(%)250 22.4 62 73 11

160 23.2 64 74 10

“1” refers to oil recovery from water flood before PPG injection“2” refers to total oil recovery from both water flood and PPG treatments

Applications

About 2000 treatments so far

Reservoirs:

Sandstone reservoirs.

Naturally fractured reservoirs.

Temperature: 30~110 ºC

Salinity: 2,900 ~ 300,000 mg/L

PPG weight: 6,600 ~88,000 lbs/well, commonly 17,600-33,000 lbs

per well

Application Cases

Case 1 Case 2Oilfield Zhongyuan, Sinopec Daqing, Petro-China

Well No. W51-75 and P-72 Xing 7-2-24reservoir Sandstone Sandstone

permeability Kavg =121 md Kmax=1200 md

salinity 150,000 mg/L 4,500 mg/L

Temp. 107 ºC 45 ºC Connected producers 3 4

Comments 2 days tracer breakthrough

Application Cases (cont.) --Design of Operations

W51-75 P-72 Xing 7-2-24

PPG Conc. 0.3 % 0.3 % 0.5 %PPG weight 13 tons 7.5 tons 15.5 tons

PPG Suspension Vol.

4,200 m3 2,500 m3 3,100 m3

Water Produced water

Injection methods Alternated injection of PPG suspension and water

Application Cases (cont.)

Injection scheme (facilities)

Electric source

Pump Mixers

Produced Jet Pump Water X7-2-24 Mixing Tank

Results

0

20

40

60

80

100

Feb-99 May-99 Aug-99 Dec-99 Mar-00

Production Tim e

wat

er c

ut (%

)

0

4

8

12

16

20

Oil

prod

uctio

n (to

ns/d

ay)

Water cut

Oil production

The performance of center producer connected with W51-75 and P-72

Case 1 Case 2

Oil increase(bbl) 22,670 29,400

Oil incr. per PPG

(bbl/lb)0.5 0.86

PPG treatment results

Lessons from Applications

Well Selection CriteriaReservoir temperature below 120 ºC, but salinity is not required;Reservoirs with high perm channels or fractures;High injectivity; High water cut and high liquid rate of connected producers;Well group with low waterflood oil recovery is preferred.

Lessons from Applications (Cont.)

PPG injection DesignPPG concentration: < 1% (0.3~0.5 %)

Injection method: alternating injection of PPG/Water.

Injection rate : low rate is suggested.

Injection pressure : monitor real-time to adjust particle size, strength and concentration.

New Development of PPG

Swelling time controllable PPG was synthesized in PEER lab

a. 24h b. 150 h c. 200 h

0

40

80

120

160

200

0 50 100 150 200 250Time (hrs)

Sw

ellin

g R

atio

New PPG PPG

25ºC 90 ºC

Future Work on PPG Technology

Mature reservoir description to characterize fracture or fracture-like streak

Transport mechanism through porous media of new PPG

IOR mechanism

Scale up laboratory results to field application

Conclusions

PPG has been successfully synthesized in the laboratory and on a commercial scale. PPG strength and size can be controlled. It has high temperature and salinity resistance.PPG can overcome some distinct drawbacks inherent to in-situ gelation systems.PPG can be added to produced water for injection into target wells. This avoids use of fresh water and so has an environmental advantage.

Conclusions (cont.)Application process and surface injection facilities are relatively simple, which can reduce operation and labor costs.Lessons from applications were presented. Proper well selection and injection procedures are important for successful PPG treatments.Field application results demonstrate that the PPG can effectively improve water conformance.

Thanks!