X-ray Computed Tomography (CT) to Scan the Structure and Characterize the Mud Cake Incorporated with Various Magnetic NPs Concentration: An Application to Evaluate the Wellbore Stability and Formation Damage.

The X-ray computed tomography method has provided unrivalled data about the characterization and evolution of the internal/external structure of materials by analyzing CTN and non-destructive imaging approach. Applying this method on the appropriate drilling-fluid ingredients plays a significant role in generating proper mud cake quality to stabilize wellbore, and avoid formation damage and filtration loss by preventing drilling fluid invasion into the formation. In this study, smart-water drilling mud containing different concentrations of magnetite nanoparticles (MNPs) was used to assess the filtration loss properties and formation impairment. Conventional static filter press, non-destructive X-ray computed tomography (CT) scan images and high-resolution quantitative measurement of CT number method were used to estimate the filtrate volume and characterize the filter cake layers, hence evaluating the reservoir damage through hundreds of merged images. The CT scan data were combined with the HIPAX and Radiant viewer digital image processing. The variation in CT number of mud cake samples under different concentrations of MNPs and without MNPs concentration were analyzed, and hundreds of 3D images as a cross-sectional profile were used. This paper highlights the importance of MNPs property in terms of minimizing filtration volume and improving mud cake quality and thickness, and hence improving the wellbore stability. From the results, a notable reduction of filtrate drilling mud volume and mud cake thickness to 40.9% and 46.6%, respectively, were recorded for drilling fluids incorporated with 0.92 wt.% of MNPs. However, this study asserts that optimal MNPs should be implemented to guarantee the best filtration property. As confirmed from the results, increasing the MNPs concentration beyond the optimal value (up to 2 wt.%) increased the filtrate volume and mud cake thickness by 3.23 and 33.3%, respectively. CT scan profile images show two layers of mud cake produced from water-based drilling fluids possessing 0.92 wt.% MNPs. The latter concentration was found to be the optimal additive of MNPs as it caused a decrease in filtration volume, mud cake thickness, and pore spaces within the structure of the mud cake. Using the optimum MNPs, the CT number (CTN) shows a high CTN and density material, and uniform compacted thin mud cake structure (0.75 mm). The produced thin mud cake layer reveals the precipitation or exchange of elemental/mineral composition during fluid-solid interaction. These results confirm that MNPs could help in avoiding or reducing the formation damage, driving away drilling fluid from the formation, and improving borehole stability.

A Critical Overview of ASP and Future Perspectives of NASP in EOR of Hydrocarbon Reservoirs: Potential Application, Prospects, Challenges and Governing Mechanisms.

Oil production from depleted reservoirs in EOR (Enhanced Oil Recovery) techniques has significantly increased due to its huge demands in industrial energy sectors. Chemical EOR is one of the best approaches to extract the trapped oil. However, there are gaps to be addressed and studied well for quality and cost consideration in EOR techniques. Therefore, this paper addresses for the first time a systematic overview from alkaline surfactant polymer ((ASP)) and future perspectives of nano-alkaline surfactant polymer ((NASP)), its synergy effects on oil recovery improvement, and the main screening criteria for these chemicals. The previous findings have demonstrated that the optimum salinity, choosing the best concentration, using effective nano-surfactant, polymer and alkaline type, is guaranteed an ultra-low IFT (Interfacial Tension). Core flood results proved that the maximum oil is recovered by conjugating nanoparticles with conventional chemical EOR methods (surfactant, alkaline and polymer). This work adds a new insight and suggests new recommendation into the EOR application since, for the first time, it explores the role and effect of nanotechnology in a hybrid with ASP. The study illustrates detailed experimental design of using NASP and presents an optimum micro-model setup for future design of NASP flow distribution in the porous media. The presence of nano along with other chemicals increases the capillary number as well as the stability of chemicals in the solution and strengthens the effective mechanisms on the EOR.

The geologic history of seawater oxygen isotopes from marine iron oxides.

The oxygen isotope composition (δ18O) of marine sedimentary rocks has increased by 10 to 15 per mil since Archean time. Interpretation of this trend is hindered by the dual control of temperature and fluid δ18O on the rocks' isotopic composition. A new δ18O record in marine iron oxides covering the past ~2000 million years shows a similar secular rise. Iron oxide precipitation experiments reveal a weakly temperature-dependent iron oxide-water oxygen isotope fractionation, suggesting that increasing seawater δ18O over time was the primary cause of the long-term rise in δ18O values of marine precipitates. The 18O enrichment may have been driven by an increase in terrestrial sediment cover, a change in the proportion of high- and low-temperature crustal alteration, or a combination of these and other factors.

Stable iron isotopes and microbial mediation in red pigmentation of the Rosso Ammonitico (mid-late Jurassic, Verona area, Italy).

The iron (Fe) isotopic composition of 17 Jurassic limestones from the Rosso Ammonitico of Verona (Italy) have been analyzed by Multiple-Collector Inductively Coupled Plasma Mass Spectrometry (MC-ICP-MS). Such analysis allowed for the recognition of a clear iron isotopic fractionation (mean -0.8 per thousand, ranging between -1.52 to -0.06 per thousand) on a millimeter-centimeter scale between the red and grey facies of the studied formation. After gentle acid leaching, measurements of the Fe isotopic compositions gave delta(56)Fe values that were systematically lower in the red facies residues (median: -0.84 per thousand, range: -1.46 to +0.26 per thousand) compared to the grey facies residues (median: -0.08 per thousand, range: -0.34 to +0.23 per thousand). In addition, the red facies residues were characterized by a lighter delta(56)Fe signal relative to their corresponding leachates. These Fe isotopic fractionations could be a sensitive fingerprint of a biotic process; systematic isotopic differences between the red and grey facies residues, which consist of hematite and X-ray amorphous iron hydroxides, respectively, are hypothesized to have resulted from the oxidizing activity of iron bacteria and fungi in the red facies. The grey Fe isotopic data match the Fe isotopic signature of the terrestrial baseline established for igneous rocks and low-C(org) clastic sedimentary rocks. The Fe isotopic compositions of the grey laminations are consistent with the influx of detrital iron minerals and lack of microbial redox processes at the water-interface during deposition. Total Fe concentration measurements were performed by Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) (confirmed by concentration estimations obtained by MC-ICP-MS analyses of microdrilled samples) on five samples, and resultant values range between 0.30% (mean) in the grey facies and 1.31% (mean) in the red facies. No correlation was observed between bulk Fe content and pigmentation or between bulk Fe content and Fe isotopic compositions. The rapid transformation of the original iron oxyhydroxides to hematite could have preserved the original isotopic composition if it had occurred at about the same temperature. This paper supports the use of Fe isotopes as sensitive tracers of biological activities recorded in old sedimentary sequences that contain microfossils of iron bacteria and fungi. However, a careful interpretation of the iron isotopic fractionation in terms of biotic versus abiotic processes requires supporting data or direct observations to characterize the biological, (geo)chemical, or physical context in relation to the geologic setting. This will become even more pertinent when Fe isotopic studies are expanded to the interplanetary realm.