Abstract
The complete characteristics knowledge of clay minerals is necessary in the evaluation studies of hydrocarbon reservoirs. Ten samples taken from two wells in a heterogeneous clastic gas reservoir formation in NE Iran were selected to conduct the transmission Fourier transform infrared spectroscopy (FTIR) tests for the clay mineralogy studies. The FTIR analysis showed that there were clear signs of clay minerals in all samples. The wavenumber region of the clay minerals in FTIR tests was detected to be 3621, 3432, 1034, and 515 cm−1 for illite, 3567, 3432, 1613, 1088, 990, 687, 651, and 515 cm−1 for magnesium-rich chlorite, 3700, 3621, 3432, 1034, 687, and 463 cm−1 for kaolinite, and 3567, 1088, 990, and 463 cm−1 for glauconite. After screening of samples by the FTIR method, the samples were then analyzed by powder X-ray diffraction (PXRD), wavelength dispersive X-ray fluorescence (WDXRF), and scanning electron microscopy (SEM). The PXRD and SEM result showed illite was by far the most common clay present. Kaolinite, magnesium-rich chlorite, and traces of smectite and the mixed-layer clays of both the illite–smectite and chlorite-smectite types were also recognized. The combination of PXRD and WDXRF results could quantify the clay abundances in the each well too. It was concluded that the FTIR analysis successfully could show the absorption bonds of all constituent clays. However, the infrared absorption spectra of mixed-layer clays overlapped those of the respective constituents of each mixed-layer minerals. This can be considered as the evidence of the usefulness of FTIR technique in the screening of the samples for the clay mineralogy studies.
Highlights
The clay minerals, even in the small amounts, strongly affect the properties of petroleum reservoirs as well as the response of most well logging tools (Attia et al 2015; Abudeif et al 2016a, 2016b, 2018; Hasan et al 2020; Radwan 2020; Radwan et al 2020; Jiu et al 2021)
The infrared absorption spectra of mixed-layer clays overlapped those of the respective constituents of each mixed-layer minerals. This can be considered as the evidence of the usefulness of Fourier transform infrared spectroscopy (FTIR) technique in the screening of the samples for the clay mineralogy studies
It was obvious that the clay minerals were present in all samples; it was decided to check the accuracy of FTIR prediction with X-ray diffraction (XRD), and XRF methods to demonstrate the clay minerals existence in the samples. It is clear from the results of the wavelength dispersive X-ray fluorescence (WDXRF) test (Table 1) that the silicon was present in the major quantities in both wells, while the aluminum oxide was moderate and the other elements such as sulfur, calcium, potassium, sodium, magnesium, and iron were present in only minor amounts
Summary
The clay minerals, even in the small amounts, strongly affect the properties of petroleum reservoirs as well as the response of most well logging tools (Attia et al 2015; Abudeif et al 2016a, 2016b, 2018; Hasan et al 2020; Radwan 2020; Radwan et al 2020; Jiu et al 2021). A comprehensive knowledge of clay mineralogy is needed for both the reservoir modeling and the interpretation of wire-line log data (Hong et al 2020; Wang et al 2020; Radwan, 2021a; Radwan et al, 2021a). The conventional XRD method needs careful sample preparation besides several specialized treatments to identify particular clay minerals (Kumar & Lingfa 2020). Such treatments run the risk of destroying or altering clays of interest (Moore & Reynolds 1989). Infrared spectroscopy (IR) is a widely used analytical technique in the geosciences studies (Stanienda 2016) and sometimes used as a screening tool to recognize the samples containing clays for more sophisticated and time-consuming procedures such as XRD. The FTIR analysis has several advantages over the XRD including: (i) the
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