Partially hydrolyzed polyacrylamide: enhanced oil recovery applications, oil-field produced water pollution, and possible solutions

Abstract

Polymers, such as partially hydrolyzed polyacrylamide (HPAM), are widely used in oil fields to enhance or improve the recovery of crude oil from the reservoirs. It works by increasing the viscosity of the injected water, thus improving its mobility and oil recovery. However, during such enhanced oil recovery (EOR) operations, it also produces a huge quantity of water alongside oil. Depending on the age and the stage of the oil reserve, the oil field produces ~ 7-10 times more water than oil. Such water contains various types of toxic components, such as traces of crude oil, heavy metals, and different types of chemicals (used during EOR operations such as HPAM). Thus, a huge quantity of HPAM containing produced water generated worldwide requires proper treatment and usage. The possible toxicity of HPAM is still ambiguous, but its natural decomposition product, acrylamide, threatens humans' health and ecological environments. Therefore, the main challenge is the removal or degradation of HPAM in an environmentally safe manner from the produced water before proper disposal. Several chemical and thermal techniques are employed for the removal of HPAM, but they are not so environmentally friendly and somewhat expensive. Among different types of treatments, biodegradation with the aid of individual or mixed microbes (as biofilms) is touted to be an efficient and environmentally friendly way to solve the problem without harmful side effects. Many researchers have explored and reported the potential of such bioremediation technology with a variable removal efficiency of HPAM from the oil field produced water, both in lab scale and field scale studies. The current review is in line with United Nations Sustainability Goals, related to water security-UNSDG 6. It highlights the scale of such HPAM-based EOR applications, the challenge of produced water treatment, current possible solutions, and future possibilities to reuse such treated water sources for other applications.

Keywords: Acrylamide; Bioremediation; Enhanced oil recovery; Partially hydrolyzed polyacrylamide; Produced water; Toxicity.

Fig. 1

The three phases of crude oil recovery from oil reservoirs

Fig. 2

The chemical structure of PAM and HPAM

Fig. 3

The chemical structure of acrylamide

Fig. 4

Microbial induced corrosion (MIC) in the oil and gas pipeline system (Modified from Chen et al., 2013)

Fig. 5

Extracellular amidase induce the bacterial degradation of PAM (Caulfield et al., ; Nyyssölä & Ahlgren, 2019)

Fig. 6

The proposed biodegradation pathway of PAM and HPAM to acrylamide (Modified from Joshi & Abed, 2017)

Fig. 7

The chemical structure of polysaccharide biopolymers (A pullulan, B schizophyllan, C Xanthan gum) (Ferreira et al., ; Lochhead, ; Sutivisedsak et al., 2013)