Preformed Particle Gel (PPG)

for Conformance Control

Baojun Bai, Yongfu Wu

Petroleum Engineering

Missouri University of Science and Technology

March 23, 2009

Missouri Energy Summit 2009

Outline

Oil Production Mechanisms Enhanced Oil Recovery (EOR) Targets Preformed Particle Gel (PPG) for Conformance Control

Gel Treatments Advantage of PPG Treatments Enhanced Oil Recovery Mechanisms Applications

Future Research Summary

Oil Production Processes

Oil Recovery Mechanisms

EOR Potential in the U.S.A

EOR Targets

Original Oil in Place in USA: 649 Billion Barrels

EOR Potential in the World

The Four Key Issues to be Resolved to Maximize Oil Recovery

Preformed Particle Gel (PPG)

for Conformance Control

What is Preformed Particle Gel (PPG)

(a) Before swelling (b) After swelling

Cross-linked polyacrylamide powder

SUPER ABSORBENT POLYMER

Why Gel Treatment

Excess water production is the most serious problem to reduce oil production as oilfields are maturing.

Improved sweep efficiency has become the most important target to improve oil recovery.

Gel Treatments are often the best choice to mitigate channeling through fractures and super-K streaks

What is Gel?

Gelant (polymer/monomer+crosslinker

+additives)

Gel

Gel Treatment to Block/Reduce Water Flow through High Permeability Zone/Streak

Near Wellbore Treatment (no crossflow)

In-depth Gel Treatment (thick heterogenous layer with crossflow)

KLKL

KhGel KhGel

KL

Gels Used for Conformance Control

In-situ gel systems: Gelant is injected into formation and gel is formed under reservoir conditions after placement. Gelation occurs in the reservoir.

Preformed gel systems: gel is formed in surface facilities before injection, then gel is injected into reservoirs. No gelation occurs in reservoir.

A Newer Trend in Gel Treatment is Using Preformed Gels

Inherent disadvantages of In-Situ Gel Crosslinking reactions are strongly affected by

Shear by pump, wellbore and porous media Adsorption and chromatography of chemical

compositions Dilution of formation water

Possible damage on unswept low

permeability oil zone of in-situ gel

Current Preformed Gel Systems

Preformed Bulk Gel: Dr. Seright/NMT, Robert Sydansk

Micro Particle Gel: µm-sized particle by Zaitoun et

al/IFP. One application in a gas storage well

Bright Water®: Nano particle by Chevron, BP and Nalco

Ten plus well pilot tests.

Preformed Particle Gel: mm-sized Grained particle,

Bai et al, bout 2,000 treatments

PPG Products

Size Adjustable: um-mm

Swelling Ratio: 30200 times original

Salt Resistance: All salt types and concentrations are acceptable

Temperature Resistance: High, to 110 ºC

Long-term Stability: more than 1 year below 110 ºC.

Oil Recovery

ER=ED×EA×EV

ER=Recovery Efficiency

EV=Vertical Sweep Efficiency

EA=Areal Sweep Efficiency

EOR Mechanisms of PPG Treatment

Biggest Impact –Selective Plugging

ED=Displacement Efficiency Some Effect

Kh=8.23 D

No.

Permeability(Darcy)

Split of Flow (percent)

Oil Recovery ( 98% water cut)

Total Oil Recovery

Before (%)

after(%)

before(%)

after(%) ）

Before (%)

After(%)

S1 8.23 91 20 70 75

46.8  64.9 0.54 9 80 22 54

Experimental Results of Parallel Core Flooding(Vertical Heterogeneity Model)

KL=0.54 D

Areal Sweep Efficiency Improvement

Before PPG Inj.

After PPG Inj.

Mainstream

Corner

Injector

Producer

a. Remaining oil distribution in main stream

b. Oil distribution at corner – Now lower

glass

oil drop

PPG

water

MICROMODEL DEMONSTRATION

More water diverted to corner after PPG injection

3cm

Experimental Results from Single SandpackDemonstrates Improved Displacement Efficiency

Core No.

K(D)

PPG Size(mesh)

Swi(%)

Oil Recovery1

(%)

Oil Recovery2

(%)

Increased Oil Recovery

(%)

No1 22.5 250 22.4 62 73 11

No2 20.6 160 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

Field Applications

About 2000 treatments so far Reservoirs:

Naturally fractured reservoirs Reservoirs without initial or hydraulic fractures. Temperature: 30~110 ºC Salinity: 2,900 ~ 300,000 mg/L

PPG amount: 1, 000 ~120,000 lbs/well, commonly 15,000-40,000 lbs/well.

First pilot in Zhongyuan, SINOPEC

0

20

40

60

80

100

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

Production Time

wa

ter

cut (

%)

0

4

8

12

16

20

Oil

pro

du

ctio

n (

ton

s/d

ay)

Water cut

Oil production

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

Increased Oil 29,151 bbl

Oil incr. per PPG

0.3 bbl of oil per lbs of

PPG

Treatment Results

Future Research

Swollen particle transport mechanisms through high permeability zones and fractures.

Development of nano- or micro-sized swelling rate controllable particle gel.

Combination of PPG treatment and other EOR methods to enhance overall oil recovery.

Summary

Up to 65% reserve is remained after waterflood.

EOR should be considered, and can extract up to

additional 25% OOIP.

PPG treatment overcome the distinct disadvantage

of traditional in-situ gel treatments.

PPG treatment is a cost-effective method to

improve oil recovery and reduce water production

Acknowledge

Financial Support from Research Partnership to

Secure Energy for America (RPSEA) under DOE

contract

Missouri University of Science and Technology