Mechanistic Aspects of Polymeric Relative Permeability Modifier Adsorption onto Carbonate Rocks

• Published in: Energy & fuels Vol. 34; no. 10; pp. 12065 - 12077
• Main Authors: Qin, Liming, Arjomand, Eghan, Myers, Matthew B, Otto, Claus, Pejcic, Bobby, Heath, Charles, Saeedi, Ali, Wood, Colin
• Format: Journal Article
• Language: English
• Published: American Chemical Society 15.10.2020
• Subjects: Fossil Fuels
• ISSN: 0887-0624; 1520-5029
• DOI: 10.1021/acs.energyfuels.0c01590

Relative permeability modifiers (RPMs) are chemicals that can be injected into a reservoir to change its fluid/gas transport characteristics. For example, RPMs can reduce the relative permeability to water in a subterranean reservoir while having minimal impact on hydrocarbon production. Most commercially available RPMs are specifically designed for silica surfaces which are dominant in sandstone reservoirs. However, the concentration of silica in carbonate rocks is very low and many of these RPMs are unsuitable for carbonate reservoirs (which hold a significant portion of the remaining 60% hydrocarbon reserves). Furthermore, carbonate reservoirs tend to have more complex permeability and porosity characteristics and as such few research publications report the utilization of RPMs in the reservoirs of this type. The main mechanism of RPMs is either chemical adsorption onto, or functionalization of, a rock surface. However, as carbonates have distinctly different chemistry compared to silica, a new RPM formulation is required. The approach reported here overcomes this obstacle by using sodium silicate to functionalize the carbonate rock surface thereby converting it into a surface that in many ways exhibits the chemistry of silica. This has been confirmed by sodium silicate adsorption tests and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) analysis. The other components consist of an amine-containing silylation reagent which reacts with the newly formed silicate surface, a polymer containing amine functional groups, and a linker molecule that reacts with the amines on the silane immobilizing the polymer. The chemistry is confirmed using five different chemical solutions to investigate their adsorption onto carbonate rocks using static tests. The results show that carbonate particles treated by the RPM have the highest adsorption weight, 7.33 mg/g and according to the measurements of X-ray photoelectron spectroscopy (XPS), the atomic percentage of Si 2p and N1s is 9.89% and 7.51% respectively, indicating the adsorption of RPM onto carbonate particles. To further verify the performance of RPM under reservoir conditions (1500 psi and 60 °C), three core flooding tests have been conducted. The results show that relative permeability to water decreased much more than oil. RRF to water in sample indinana-2 can reach up to 5.21, but RRF to oil is less than 2. The disproportionate ratio (RRFbrine/RRFoil) is 3.1, indicating the good performance of RPM under reservoir conditions. This work first introduced sodium silicate and APTES to make polyacrylamides as a new RPM material strongly stabilized onto carbonate rock surfaces, which provided further insights into the effectiveness of this approach applied in carbonate reservoirs.