**3. Gelling polymer system screening**

Field tests, both onshore and offshore, carried out in North America, Asia, Africa, Europe, and South America, showed that BrightWater™ submicrogels can travel long distances, allowing

Preformed particle gels (PPG) and partially preformed gel systems are millimeter-sized preformed gels (10 μm to mm) based on acrylamide, polyacrylamide copolymers (e.g. PAM, PHPA, PAtBA, and PAM-AMPS), modified superabsorbent polymers (SAP), or biopolymers (e.g. chitosan and starch) cross-linked with metal ions (e.g. chromium acetate), organic compounds (e.g. N-N′-methylene-bis-acrylamide and PEI) or biopolymers (e.g. chitosan and

The PPGs are prepared by solution polymerization/cross-linking followed by drying, crushing, and sieving the preformed bulk gels to the desired particle size. In the field, prior to be injected into the reservoir, these preformed particles swell in water forming strong and stable

PPGs were applied in China for more than 2000 wells to reduce the water production in mature water-flooded reservoirs. Since PPGs particles are relatively large, their application is

The PPGs have many advantages over other conformance-improvement treatments, such as

• high thermal and chemical stability at temperatures up to 120°C and salinities up to

• ease preparation in surface facilities (e.g. produced water can be used to prepare them).

In order to improve the PPG swellability, thermal stability and mechanical strength (modulus, elasticity, and deformability) nanoclays (e.g. kaolinite, laponite, and montmorillonite) can

pH-sensitive gel systems are micrometer-sized particle gels (1–10 μm) that are based on anionic polyelectrolytes (e.g. PHPA and poly(acrylic acid)) cross-linked by allyl ethers of

In these systems, the pre–cross-linked microgels injection is carried out at low pH values. The pre-addition of hydrochloric acid or citric acid is necessary to reduce the viscosity of the microgels before injection − the low-pH coils polymer chains reducing the gelant viscosity. Once deep into the reservoir, the gel microglobules swell (polymer chains uncoil absorbing

the permeability control of the reservoir at great depths [69, 71–73].

*2.2.4. Preformed particle gels (PPG)*

hydrogels in surface facilities [74–76].

be added to their formulation [75].

polyols (e.g. allyl pentaerythritol).

*2.2.5. pH-sensitive gel systems*

limited to reservoirs with fractures or fracture-like channels.

• insensitivity to reservoir minerals and formation water salinity;

300,000 mg/L TDS (including multivalent cations); and

• good size distribution control of particles (μm–cm);

starch) [74, 75].

78 Hydrogels

[74, 76]:

The success of a hydrogel-conformance-improvement treatment depends on the correct assessment of the nature of the conformance problem and on the selection of an effective gelling system.

Reservoir conformance problems that can be treated with gelling polymer systems are basically [21, 22]:


The screening and selection of the most appropriate gelling polymer system for the conformance-improvement treatment of an oil reservoir can be done using different laboratory tests (i.e. bottle tests, continuous and oscillatory rheological measures, and core flooding experimental tests) to access information on the gelation time and final gel strength, as well as the short- and long-term stability of gelling polymer systems under specific reservoir conditions − temperature, salinity, pH value of the formation water, and the presence of either carbon dioxide (CO<sup>2</sup> ) or hydrogen sulfide (H<sup>2</sup> S) [20, 35, 53, 80–83].

Gelling polymer systems used to control the anisotropic permeability profile of oil reservoir should:

• behave as moderately pseudoplastic fluids, with viscosity between 10 and 30 mPa.s at a constant shear rate of 7 s−1 to ensure good injectivity and propagation in the porous medium. These injectivity and propagation parameters can be obtained by continuous rheological tests [56, 84, 85];

**Author details**

Rio de Janeiro, RJ, Brazil

2010;**65**(6):859-878

Technology. 2006;**29**(6):117

2007;**55**(3):294-300

**References**

Fernanda G. C. Tessarolli\*, Ailton S. Gomes and Claudia R. E. Mansur

Institute of Macromolecules (IMA), Federal University of Rio de Janeiro (UFRJ),

[1] Sydansk RD, Romero-Zerón L. Reservoir conformance improvement. Richardson:

Hydrogels Applied for Conformance-Improvement Treatment of Oil Reservoirs

http://dx.doi.org/10.5772/intechopen.73204

81

[2] Liu Y, Bai B, Wang Y. Applied technologies and prospects of conformance control treatments in China. Oil and Gas Science and Technology D'IFP Energies Nouvelles.

[3] Kabir AH. Chemical water & gas shutoff technology: An overview. In: SPE Asia Pacific

[4] Feng Y, Tabary R, Renard M, Le Bon C, Omari A, Chauveteau G. Characteristics of microgels designed for water shutoff and profile control. In: International Symposium

[5] Hu S, Zhang LH, Yu HJ, Wei W, Luo J. Development and prospect of the profile control/ water shutoff technology in reservoir high-capacity channels. Drilling and Production

[6] Ma S, Dong M, Li Z, Shirif E. Evaluation of the effectiveness of chemical flooding using heterogeneous sandpack flood test. Journal of Petroleum Science and Engineering.

[7] Moradi-Araghi A. A review of thermally stable gels for fluid diversion in petroleum

[8] Sengupta B, Sharma VP, Udayabhanu G. Gelation studies of an organically cross-linked polyacrylamide water shut-off gel system at different temperatures and pH. Journal of

[9] Tokita M, Nishinari K. Gels: structures, properties, and functions: Fundamentals and

[10] Doe PH, Moradi-Araghi A, Shaw JE, Stahl GA. Development and evaluation of EOR polymers suitable for hostile environments Part 1: Copolymers of vinylpyrrolidone and

[11] Vossoughi S. Profile modification using in situ gelation technology—A review. Journal

production. Journal of Petroleum Science and Engineering. 2000;**26**(1):10

Petroleum Science and Engineering. 2012;**81**:145-150

applications. Vol. 136. Springer-Verlag Belin Heidelberg; 2009

acrylamide. SPE Reserv Eng SPE-14233-PA. 1987;**2**(04):461-467

of Petroleum Science and Engineering. 2000;**26**(1):199-209

\*Address all correspondence to: fernandagcordeiro@gmail.com

Improved Oil Recovery Conference, SPE-72119-MS. 2001

Society of Petroleum Engineers; 2011

on Oilfield Chemistry, SPE-80203-MS. 2003


Other parameters that should also be considered during the screening are the toxicity and cost of the gelling system components, as well as their thermal, mechanical, and biological stability, retention, and adsorption on reservoir rock.

**Figure 3.** Bottle testing characterization of PAM-PEI hydrogels using the Sydansk's gel-strength code.
