Clay Minerals in Hydrocarbon Reservoir Rocks and Their Interactions with Crude Oils and Brines:

Abstract

Low saline water flooding (LSWF) is an emerging, low-cost and environment friendly technique for enhanced oil recovery (EOR) from hydrocarbon reservoirs. However, the mechanism behind this incremental oil recovery is still debated. Detailed molecular level insights of the interaction among the reservoir rock-crude oil-brine are very crucial for designing effective low saline water for maximizing oil recovery. Present research work is an attempt to investigate the detailed characterization of clay minerals and crude oils present in the different reservoir rocks followed by understanding the interaction phenomenon which takes place among different clay minerals (using kaolinite, montmorillonite, and clay minerals present in crystalline basement rock), crude oils (collected from Cambay basin, India), and different concentrations of brine (using NaCl, CaCl2, and MgCl2) for designing effective low saline water (LSW). An attempt has been made to understand the macromolecular level interaction among clay-bearing crystalline basement rock, crude oil, and saline water for designing effective flooding fluid for EOR which is very limited in the existing literature. In this thesis, different analytical techniques were used giving special emphasis to various optical spectroscopic techniques (Fourier transform infrared (FTIR), UV-visible, fluorescence and gas chromatography- mass spectroscopy) for understanding macromolecular level interaction phenomena during LSWF by performing lab-scale experiments. The key results connote that the kaolinite and montmorillonite clays are the predominating clay species in most of the hydrocarbon reservoir rocks. The clay minerals are found primarily, as authigenic pore-filling and pore bridging material in the reservoir rocks. The macromolecular level characterization marks the difference among the studied crude oils in terms of their SARA distribution and presence of polycyclic aromatic hydrocarbon (PAH) with fused aromatic ring (FAR) structures associated with the polar oil components. These components particularly, the asphaltenes are adsorbed onto the surfaces of clay minerals where the interaction varies with the variation of the PAH structures present in the asphaltenes of the crude oil. The study reveals that (i) clay specific designing (selection of cation type and salinity range) of LSW flooding fluid is required for optimum oil recovery from the hydrocarbon reservoir which needs a detailed characterization of clay minerals present inside the reservoir rock (ii) the macromolecular level characterization of the crude oil and its components (saturates, aromatics, resins, and asphaltenes) particularly, the PAH (ring size) structures associated with the polar components is one of the key requirements prior to designing the injection fluid as LSW is efficient to remove polar oil components rich in 3-6 ring PAH structures (iii) sodium (Na+) bearing low saline water is most effective for enhanced oil recovery for clay-laden reservoir during LSWF compared to other (Ca++, Mg++) cations bearing LSW.