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In-situ combustion is a thermal recovery technique in which a part of the heavy oil in place is burnt to generate heat. This heat brings about a reduction in viscosity of the crude oil to lead to the improvement of the mobility and hence oil production rate and recovery. Typical combustion front moves slow (some cm/day) through reservoir matrix (pores) by consuming the fuel as it moves ahead. The combustion zone is often a few centimeters in thickness and it has a temperature up to 700-800oC. The hydrothermal conditions that occur in front of and behind the combustion zone may generate chemico-mineralogical transformations following or not from a new minerals forming. In the paper the authors emphasize for the first time calcium silicates hydrate forming in the matrix of siliciclastic rocks from oil reservoirs exploited by in-situ combustion.

A sol–gel synthesis technique was employed for the preparation of anatase phase {001}-TiO2/Au hybrid nanocomposites (NCs). The scalable, schematic, and cost-efficient method was successfully modified using HF and NH4OH capping agents. The photocatalytic activity of the as-synthesized {001}-TiO2/Au NCs were tested over 2-cycle degradation of methylene blue (MB) dye and pharmaceutical active compounds (PhACs) of ibuprofen and naproxen under direct sunlight illumination at 35 °C and 44,000 lx. Transmission electron microscopy (TEM), high resolution transmission electron microscopy (HR-TEM), fast Fourier transform (FFT), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDS), and ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS) were employed for the characterization of the as-prepared sample. The characterization results from the TEM, XPS, and XRD studies established both the distribution of Au colloids on the surface of TiO2 material, and the presence of the highly crystalline structure of anatase {001}-TiO2/Au NCs. Photodegradation results from the visible light irradiation of MB indicate an enhanced photocatalytic performance of Au/TiO2 NCs over TiO2. The results from the photocatalytic activity test performed under direct sunlight exposure exhibited promising photodegradation efficiencies. In the first cycle, the sol–gel synthesized material exhibited relatively better efficiencies (91%) with the MB dye and ibuprofen, while the highest degradation efficiency for the second cycle was 79% for the MB dye. Pseudo first-order photodegradation rates from the first cycle were determined to be comparatively slower than those from the second degradation cycle.

Developing and producing of the heavy crude oil involved significant economic and technological challenges. The oil industry ability to prospect and capitalize the huge world heavy oil resources both economically and environmentally friendly will be crucial in helping meet future energy needs. Thermal oil recovery is one of the three types of techniques belonging to Enhanced Oil Recovery. It is applied for increasing the cumulative of crude oil that can be produced in an oil field. One of the oldest thermal oil recovery is in-situ combustion or fireflooding applied for the first time about 100 years ago. Despite in-situ combustion has not found widespread acceptance among operators like other thermal processes (such as steam injection), analysis of the successful projects indicates that the process is applicable to a wide range of oil reservoirs, especially to heavy crude oils. An important monitoring parameter of thermal oil recovery process is represented by thermal regime especially in heavy oil fields in which a high-temperature regime must be occur as the in-situ combustion to be successful. In the paper the authors are using thermal analysis (thermogravimetric and thermodifferential analysis) for investigation of the thermal regime involved in the production process of an oil reservoir by in-situ combustion.