Incorporation of Partially Hydrolyzed Polyacrylamide With Zwitterionic Units and Poly(Ethylene Glycol) Units Toward Enhanced Tolerances to High Salinity and High Temperature

Partially hydrolyzed polyacrylamide (HPAM) was widely implemented to improve the rheological properties of displacing fluids, but the high temperature and salinity of the reservoir brine limited their applications. Herein, copolymers including HPAM, zwitterion-modified HPAM (z-HPAM), PEG-modified HPAM (p-HPAM), and zwitterion/PEG-modified HPAM (zp-HPAM) were prepared by free radical polymerization in an aqueous solution. The viscosity of these copolymers under different temperature and salinity was measured in aqueous solution. It is found that the viscosity of the HPAM under the harsh condition (90oC, 20 × 104 mg/L salinity) is only 9.6% of that value under the normal condition (25oC, pure water), while the z-HPAM can significantly improve salt resistance by the effects of salting-in effect and intermolecular electrostatic crosslinking, showing a viscosity retention of 22.9% under the harsh condition. The addition of PEG-containing monomer can strengthen hydrogen bonding between the polymer chains and form a sterically ordered structure with improved salinity and temperature resistance. The synergistic effect of zwitterion units and PEG units endows the zp-HPAM with good salinity and temperature resistance; thus, the sample viscosity under the harsh condition remains 170 mPa s, which retains 29% of the value under the normal condition. The enhanced rheology properties of the zp-HPAM under the harsh condition are significant for the enhanced oil recovery of water-soluble polymer flooding.

Temperature Dependence of the Shear-Thinning Behavior o Partially Hydrolyzed Polyacrylamide Solution for Enhanced Oil Recovery

The viscosity of injection fluid is a critical parameter that should be considered for the design and evaluation of polymer flood, which is an effective and popular technique for enhanced oil recovery (EOR). It is known that the shear-thinning behavior of EOR polymer solutions is affected by temperature. In this study, temperature dependence (25–70 °C) of the viscosity of a partially hydrolyzed polyacrylamide solution, the most widely used EOR polymer for oil field applications, was measured under varying conditions of the polymer solution (polymer concentration: 500–3000 ppm, NaCl salinity: 1000–10,000 ppm). Under all conditions of the polymer solution, it was observed that the viscosity decreases with increasing temperature. The degree of temperature dependence, however, varies with the conditions of the polymer solution. Martin model and Lee correlations were used to estimate the dependence of the viscosity of the polymer solution on the polymer concentration and salinity. In this study, we proposed a new empirical model to better elucidate the temperature dependence of intrinsic viscosity. Analysis of the measured viscosities shows that the accuracy of the proposed temperature model is higher than that of the existing temperature model.

Water shut off gel

Injection of Partially Hydrolyzed Polyacrylamide gels using inorganic crosslinking agents has proven to be one of the best methods for isolating water and enhancing oil recovery. Partially hydrolyzed polyacrylamide forms a gel structure in the presence of trivalent metal ions such as Cr3+, Al3+, which act as a crosslinker. In this case, a sequential injection of a polymer solution and a crosslinking agent is carried out into the formation and the gel is formed directly in the formation. Numerous successful examples of the implementation of this technology to reduce the water cut of the produced products were the basis for the development of a new gel composition, taking into account the disadvantages of the existing ones. The paper presents the results of laboratory studies on core material using the proposed gel composition based on a partially hydrolyzed polyacrylamide polymer and various crosslinking agents (note: thiourea / K2Cr2O7).

COMPARATIVE ANALYSIS OF CARBOXYMETHYL CELLULOSE AND PARTIALLY HYDROLYZED POLYACRYLAMIDE – LOW-SOLID NONDISPERSED DRILLING MUD WITH RESPECT TO PROPER-TY ENHANCEMENT AND SHALE INHIBITION

During drilling, different problems are encountered that can interfere with smooth drilling processes, including the accumulation of cuttings, reduced penetration rates, pipe sticking, loss of wellbore stability, and loss of circulation. These problems are generally encountered with conventional drilling mud, such as the bentonite–barite mud system. Formation damage is the most common problem encountered in bentonite mud systems with high solid content. In this work, we aimed to formulate two low-solid nondispersed (LSND) muds: carboxymethyl cellulose (CMC)–LSND mud and partially hydrolyzed polyacrylamide (PHPA)–LSND mud. A comparative analysis was performed to evaluate their property enhancements. LSND muds aid in maintaining hole stability and proper cutting removal. The results of this work show that the addition of both CMC and PHPA helps to improve drilling fluid properties; however, the PHPA–LSND mud was found to be superior. Shale swelling is a major concern in the petroleum industry, as it causes various other problems, such as pipe sticking, low penetration rates, and bit wear. The effect of these two LSND polymer muds in inhibiting shale swelling was analyzed using shale collected from the Champhai district of Mizoram, India.