Assessment of Enhanced-Oil-Recovery-Chemicals Production and its Potential Effect on Upstream Facilities
Authors: AlSofi Abdulkareem M. , AlKhatib Ali M. , Al-Ajwad Hassan A. , Wang Qiwei , Zahrani Badr H. 
Published: January 2019

Review of past chemical-enhanced-oil-recovery (EOR) projects illustrates that chemical-EOR implementation can result in produced-fluid-handling issues. However, in all projects such issues were resolved, mainly through a combination of improved demulsifiers and oversized vessels. In previous work, we have demonstrated the potential of surfactant/polymer flooding for a high-temperature/high-salinity carbonate. In consideration of future plans to pilot the process, further assessments were conducted to evaluate any side effects of these EOR chemicals on upstream facilities and determine mitigation plans if needed. In this work, we initially conduct a critical review of past experience. Then, we investigate the surfactant/polymer compatibility with the additives used in processing facilities for demulsification and scale and corrosion inhibition as well as the possible effect of surfactant/polymer on oil/water separation, metal corrosion, and scale inhibition. For this purpose, we first perform a sensitivity-based simulation study to estimate the volumes of produced EOR chemicals. Second, a compatibility study is conducted to evaluate EOR chemical compatibility with oilfield additives (i.e., demulsifier, corrosion inhibitor, and scale inhibitor). Third, bottle tests are conducted using surfactant/polymer solutions prepared in both injection and produced water to evaluate the effect of EOR chemicals on oil/water separation. Separated-water qualities are also evaluated using solvent extraction followed by ultraviolet (UV) visibility testing. Fourth, static autoclave and dynamic rotating tests are performed to evaluate the possible side effects of EOR chemicals on corrosion inhibition. Finally, static bottle and dynamic tube tests are performed to evaluate the possible side effects of EOR chemicals on scale inhibition; these observations are supported by characterization of precipitates using environmental scanning electron microscopy (ESEM) and X-ray diffraction (XRD).

Depending on simulation, the peak polymer and surfactant concentrations at the separation plant are 83 and 40 ppm, respectively. The sensitivity study suggests a worst-case scenario in which peak polymer and surfactant concentrations of 174 and 128 ppm are produced. Compatibility testing confirms the compatibility of EOR chemicals with the additives used in upstream facilities. In those tests, neither precipitation nor phase separation is observed. Bottle tests indicate an overall negligible effect on oil/water-separation speed. However, analyses of separated-water quality indicated a noteworthy deterioration in separated-water qualities. Oil-in-water concentrations increase from 100 to 750 ppm and from 300 to 450 ppm at injection- and produced-water salinities, respectively. Furthermore, corrosion tests suggest that surfactant/polymer presence results in a significant reduction in corrosion rates by 70 and 86% at static and dynamic conditions, respectively, without any pitting issues. Finally, static and dynamic scale-inhibition studies performed at exacerbated conditions suggest that EOR chemicals can reduce the effectiveness of scale inhibitors. In static scaling tests, the effectiveness of the base polyacrylate inhibitor diminishes completely. However, the same degree of inhibition was achieved by switching to phosphonate inhibitors, but at a slightly higher dosage between 5 and 15 mg/L. In dynamic scaling tests, the base polyacrylate inhibitor failed at all tested dosages up to 100 mg/L. However, the alternative phosphonate inhibitors passed at dosages between 20 and 45 mg/L. Such effects can be attributed to changes in scale morphology and polymorphs, as demonstrated by the XRD and ESEM results.

On the basis of those results, we conclude that the selected surfactant/polymer implementation will have a manageable effect on separation facilities. Finally, this work provides an experimental protocol to evaluate the potential side effects of a chemical-EOR process on upstream facilities.