A comprehensive review ofin situpolymer hydrogels for conformance control of oil reservoirs

Abstract

In fractured reservoirs, fluids injected Enhanced Oil Recovery (EOR) are channeled through the fracture zones and travel through highly permeable regions, failing to displace part of the oil, and decreasing oil recovery efficiency. To solve these problems, the conformance control technique is now widely used, as it allows the reservoir to be swept totally, similar to the ideal condition. In this context, polyacrylamide-based polymer gel systems can be used to block the high-permeability regions of the rock matrix, forming in situ hydrogels that block the rock pores, avoiding the channeling of the fluids, and increasing the oil production. These polyacrylamide-based hydrogels can be crosslinked by inorganic (metal ions) or organic substances, and various systems are used for conformance control. Due to the greater stability of the bond formed between the polymer and the organic crosslinker, these systems are now used in higher temperature reservoirs. In order to produce hydrogels with higher resistance to severe salinity and temperature conditions, nanoparticles are applied to form systems with good mechanical resistance, and high thermal stability. These have presented promising results for conformance control.

Investigation of acid pre-flushing and pH-sensitive microgel injection in fractured carbonate rocks for conformance control purposes

“…During waterflooding, the injected water rapidly flows through fractures and high permeable strata and breaks through in production wells. Thus, this early water breakthrough leaves a high residual oil saturation in low permeable areas (rock matrix) and reduces ultimate oil recovery [1][2][3]. One remedy to overcome this early water breakthrough problem is implementing gel treatment methods like preformed particle gels [4,5], pH-sensitive microgels [6,7], pH-insensitive polymeric solutions [8], or other smart polymers [9].…”

Behavior of partially hydrolyzed polyacrylamide/polyethyleneimine reinforced with coal fly ash for preformed particle hydrogels

“…[1,2] In this scenario, fluids tend to move inefficiently through the reservoir, and in the case of carrier fluids, movement occurs through preferential regions, which decreases oil production and increases water production. [3,4,5] The chemical treatment to reduce water production while preserving oil flow is known as conformance control. [5] Among other substances, polymeric materials and their crosslinked gels have been found to be economical and effective for water control in EOR in many oilfields.…”

“…[3,4,5] The chemical treatment to reduce water production while preserving oil flow is known as conformance control. [5] Among other substances, polymeric materials and their crosslinked gels have been found to be economical and effective for water control in EOR in many oilfields. [6] These systems are injected into a reservoir formation with the purpose of reducing water production, diverting it to areas not previously crossed with higher oil saturation.…”

Dynamic and static gelation behavior of phenol formaldehyde resin gel system in ampoule bottles and porous media

“…Because of long gelation time, PFR gel could be used conveniently in a range of indepth treatments in matrix as well as in fractured formations. To verify the applicability of hydrogel in conformance control, it is important to evaluate the gelling behaviors, such as: gelation time, gel strength and stability (de Aguiar et al, 2020). The bulk gelation time was an important influence to choose pumping time.…”