Chelating agents show very effective performance in different applications in the upstream oil and gas industry. This study presents a critical review of the application of chelating agents in acidizing, scale removal, filter cake removal, wettability alteration, enhanced oil recovery (EOR), and hydraulic fracturing treatments. The advantages and disadvantages of using several types of chelating agents for improving the well/reservoir productivity and enhancing the oil recovery from sandstone and carbonate reservoirs are discussed. Also, detailed comparisons between different chelating agents and their applications in many oil and gas areas are presented. Moreover, the combination of chelating agents with different chemicals to achieve better performance is addressed. Hydroxy amino carboxylic acids [such as ethylenediaminetetraacetic acid (EDTA) and glutamic acid diacetic acid (GLDA)] have replaced conventional acids, such as hydrochloric acid (HCl), hydrofluoric acid (HF), and organic acids, at high temperature and salinity conditions to stimulate carbonate and sandstone reservoirs without any side effects on the formation integrity. Furthermore, diethylenetriaminepentaacetic acid (DTPA) and GLDA are effective in removing different types of scales, such as carbonate, sulfate, and sulfides, without releasing hydrogen sulfide (H 2 S) and using corrosion inhibitors. Also, DTPA, EDTA, and GLDA are very active in dissolving filter cake layers formed by different drilling fluids. Aminopolycarboxylic groups can be injected into sandstone and carbonate reservoirs to adjust the wettability conditions and enhance oil recovery. Chelating agents, such as GLDA, EDTA, and DTPA, optimize the fracture conductivity and, meanwhile, minimize the number of additives in hydraulic fracturing, which significantly cut the cost of the operation. Overall, chelating agents are economically attractive chemicals for various upstream operations since produced, and seawater can be used without further treatment.

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Fine, small-size, drilled cuttings, if not properly separated using mud conditioning equipment at the surface, are circulated with the drilling fluid from the surface to the bottom hole. These drilled cuttings have a significant effect on the drilling fluid properties and filter cake structure. During drilling long lateral sandstone formations, different cuttings with varied properties will be generated due to sandstone formations being heterogeneous and having different mineralogical compositions. Thus, the impact of these cuttings on the drilling fluid and filter cake properties will be different based on their mineralogy. In this paper, the effect of different sandstone formation cuttings, including arenite (quartz rich), calcareous (calcite rich), argillaceous (clay rich), and ferruginous (iron rich) sandstones, on the filter cake and drilling fluid properties was investigated. Cuttings of the mentioned sandstone formations were mixed with the drilling fluid to address the effect of these minerals on the filter cake thickness, porosity, and permeability. In addition, the effect of different sandstone formation cuttings on drilling fluid density and rheology, apparent viscosity (AV), plastic viscosity PV), and yield point (YP) was investigated. High-pressure high-temperature (HPHT) fluid loss test was conducted to form the filter cake. The core sample’s petrophysical properties were determined using X-ray fluorescence (XRF) and X-ray diffraction (XRD) techniques and scanning electron microscopy (SEM). The results of this work indicated that all cutting types increased the rheological properties when added to the drilling fluid at the same loadings but the argillaceous sandstone (clay rich) has a dominant effect compared to the other types because the higher clay content enhanced the rheology. From the filter cake point of view, the ferruginous sandstone improved the filter cake sealing properties and reduced its thickness, while the argillaceous cuttings degraded the filter cake porosity and permeability and allowed the finer cuttings to penetrate deeply in the filter medium.