Abstract
Excessive water production from hydrocarbon reservoirs is considered as one of major problems, which has numerous economic and environmental consequences. Polymer-gel remediation has been widely used to reduce excessive water production during oil and gas recovery by plugging high permeability zones and improving conformance control. In this paper, we investigate the performance of a HPAM/PEI (water-soluble Hydrolyzed PolyAcrylaMide/PolyEthyleneImine) polymer-gel system for pore space blockage and permeability reduction for conformance control purpose. First, the gel optimum composition, resistance to salt and long life time are determined using bottle tests as a standard method to specify polymer-gel properties. Then the performance and stability of the optimized polymer-gel are tested experimentally using coreflood tests in sandpack core samples. The effects of different parameters such as gel concentration, initial permeability of the cores, and formation water salinity on the final permeability of the cores are examined. Finally, the gel flow-induced local porosity changes are studied in both a sandpack core and a real carbonate sample using grayscale intensity data provided from 3D Computed Tomography (CT) images in pre- and post-treatment states. The results show that the gel system has a good strength at the middle formation water salinity (in the range of typical sea water salinity). In addition, despite a higher performance in high permeability cores, the gel resistance to degradation in such porous media is reduced. The CT images reveal that the initial porosity distribution has a great influence on the performance of the gel to block the pore space.
Highlights
Water produced during the production of hydrocarbons from underground formations constitutes the petroleum industry’s most important waste stream on the basis of volume (Reynolds and Kiker, 2003)
We focus on the evolution of pore space and permeability induced by polymer-gel treatment in this study
Each gel system requires a minimum concentration of polymer, called the Critical Overlap Concentration (COC), to form the gel structure
Summary
Water produced during the production of hydrocarbons from underground formations constitutes the petroleum industry’s most important waste stream on the basis of volume (Reynolds and Kiker, 2003). This problem is intensified in mature oil fields when the reservoir is subject to long water flooding. Water production creates additional costs due primarily for separation, handling and disposal (Seright et al, 2003) It may cause high levels of corrosion and scales, inevitably bring about increased load on fluid transport pipelines and facilities (Imqam and Bai, 2015), and pose environmental concerns due to the presence of toxic elements such as mercury and arsenic in the water.
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