Polymer Systems for Water Shutoff and Profile Modification: A Review Over the Last Decade

Abstract

Unwanted water production is a serious issue in oil-and gas-producing wells. It causes corrosion, scale, and loss of productivity. One method of treating this problem is to chemically reduce unwanted water. This paper discusses the use of polymer systems for this purpose and presents a thorough review of available literature over the last decade. In this paper, field-application data for various polymer systems are summarized over the range of 40 to 150 C (104 to 302 F). These applications cover a wide range of permeabilities from 20 to 2,720 md in sandstone and carbonate reservoirs around the globe. Moreover, the review revealed that the last decade of developments can be categorized into two major types. The first type is polymer gels for total water shutoff in the near-wellbore region, in which a polymer is crosslinked with either an organic or an inorganic crosslinker. The second type is concerned with deep treatment of water-injection wells diverting fluids away from high-permeability zones (thief zones). These thief zones take most of the injected water, which results in a large amount of unrecovered oil. For the total-blocking gels, various systems were identified, such as polyurethane resins, chromium (Cr 3þ ) crosslinking terpolymers, Cr 3þ crosslinking foamed partially hydrolyzed polyacrylamide (PHPA), and nanoparticle polyelectrolyte complexes (PECs) sequestering Cr 3þ for elongation of its gelation time with PHPA. In addition, polyethylenimine (PEI) was identified to crosslink various polyacrylamide-(PAM-) based polymers. The Petróleos de Venezuela S.A. (PDVSA) Research and Development Center developed a PAM-based thermally stable polymer and an organic crosslinker. The system is applicable for a wide temperature range from 50 to 160 C (130 to 320 F).For the deep modification of water-injection profiles in waterinjection wells, two systems were identified: microspheres prepared from PAM monomers crosslinked with N,N 0 -methylenebisacrylamide and microspheres produced by crosslinking 2-acrylamido-2-methylpropane sulfonic acid (AMPS) with diacrylamides and methacrylamides of diamines (thermally activated microparticles known as Bright Water). This paper highlights all major developments in these areas. Important Factors for Successful CITsThe identification of the water source is a key factor for successful CITs. The characterization of water production can be performed

Modelling Gelation Time of Organically Cross-linked Water-shutoff Systems for Oil Wells

“…Water production affects the economics of producing wells as it has to be treated and disposed of in an environmentally friendly manner at an additional cost [3,5]. Produced water cost the petroleum industry about $45 billion in 2002 [5,6], and this could be on the increase with development of additional wells. High water cut comes with its associated problems such as corrosion, sand production, scale formation and loss of productivity [1,[7][8][9].…”

“…Excessive water production can be controlled either by mechanical or chemical means [6,13]. The mechanical methods include using hardware or cement as mechanical seals or isolations to control water production, coning control through draw-down reduction and coproduction and downhole separation.…”

“…Researchers [1,6,[13][14][15][16] have identified polymer gels for near wellbore area (organically or inorganically crosslinked) and microgels for deep profile modification (Bright water and Methylene bisacrylamide Aggregates) as the broad categories of chemicals for water sealants in wells producing excessive and unwanted water. According to Watters, Kabir, Sydansk, these broad categories include; inorganic gels, resins or elastomers, monomer based systems, polymer gels, viscous systems, bio-polymers and foam gel among others [1,13,17,18].…”

“…The gelation time of water-shutoff systems is a function of the concentrations of polymer (base gel), cross-linker concentration, temperature, salinity of mixing water and pH of the fluid system among others [6]. Temperature has an important effect on the rheological properties of polymeric melts, just as it does on polymeric solids.…”

“…It was concluded that increasing degree of salinity increased the gelation time of organically crosslinked water-shutoff systems. El-Karsani, Reddy BR, Al-Muntasheri and Das concluded that increasing the polymer and cross-linker concentrations resulted in a decrease in the gelation time of water-shutoff systems [4,6,9,14,20].…”