In situ chemical oxidation (ISCO) typically delivers oxidant solutions into the subsurface for contaminant destruction. Contaminants available to the oxidants, however, are limited by the mass transfer of hydrophobic contaminants into the aqueous phase. ISCO treatments therefore often leave sites with temporarily clean groundwater which is subject to contaminant rebound when sorbed and free phase contaminants leach back into the aqueous phase. Surfactant Enhanced In situ Chemical Oxidation (S-ISCO R⃝ ) uses a combined oxidant-surfactant solution to provide optimized contaminant delivery to the oxidants for destruction via desorption and emulsification of the contaminants by the surfactants. This article provides an overview of S-ISCO technology, followed by an implementation case study at a coal tar contaminated site in Queens, New York. Included are data points from the site which demonstrate how S-ISCO delivers desorbed contaminants without uncontrolled contaminant mobilization, as desorbed and emulsified contaminants are immediately available to the simultaneously injected oxidant for reaction. c⃝
Removing oil-based mud (OBM) filter cake is a difficult task. Low removal efficiency of filter cake may result in pay zone damage, including drilling fluid filtrate incompatibilities with reservoir fluids, fines migration, and undesirable change of permeability. This paper proposes a cost-effective and single-stage application of a new surfactant/oxidant system to enhance the removal efficiency of OBM filter cake. A qualitative wettability experiment was performed to test wetting property of OBM emulsion before and after being cleaned by non-ionic surfactants. Phase behavior of the new surfactant/oxidant system was also shown when the variables were the concentration and type of coated persulfates. Filter press simulated various high-pressure/high-temperature (HP/HT) well conditions in laboratory to form and remove the OBM filter cakes. Average permeability ratio (Kfinal / Kinitial) of Berea sandstone disks was calculated by static filtration test to show the degree of formation damage. Surfactant used in the new removal system ensures OBM emulsion to be water-wet and promotes it to flow more easily in contact with the rock surface. Coated persulfate can be circulated out of wellbore after the removal work, based on its low density and tightly coated property. HP/HT filter cake removal tests indicate the optimized new system can disperse and remove the filter cake by up to 98 wt% removal efficiency. The optimized surfactant/oxidant system affects the formation permeability slightly because Kfinal / Kinitial ratio is consistent in the 0.99~1.09 range. With optimized formulation and soaking time, the cleaning solutions will benefit the oilfield industry significantly by removing OBM filter cake under challenging well conditions. Cost-Effective and single-stage application of the new removal system makes the oilfield industry more efficient and economical to remove OBM filter cake. The new surfactant/oxidant system minimizes the effects of drilling fluid on formation properties, based on its compatibility with OBM emulsions, quick removal steps, high removal efficiency, and acceptable Kfinal / Kinitial results.
The production and transportation of heavy and extra-heavy crude oil are two of the paramount concerns in the oil industry due to the difficulties associated with heavy crude oil high viscosity. One of the most efficient techniques to improve the recovery and the transportability of such oil is to reduce its viscosity through dilution that can be applied solely or via thermal methods.In the present work, a new type of plant-based diluent is proposed, and its efficacy in heavy oil viscosity reduction for different concentrations, temperatures and shear rates is studied. Various concentrations of diluent, ranging from 5 to 25 wt%, are added to heavy-oil samples with different concentrations of asphaltene and viscosity, ranging from 48000 to 65000 cp in ambient temperature. A rotational viscometer was then employed to the measure viscosity of the prepared samples at the temperature range of 70 to 190°F and a shear rate of 3 to 50 s Ϫ1 .The application of the proposed diluent led to promising results in that in caused the viscosity of the heavy oil samples to reduce by 93% in 75°F and 85% in 190°F with 20 wt% of diluent. To compare the performance of the proposed solvent and the common viscosity-reducing solvents, heavy oil samples were diluted with xylene and toluene with the same concentrations. Results indicated that the application of proposed diluent outperformed all of the commonly used solvents in terms of decreasing viscosity. The application of 20 wt% of the proposed diluent led to a 93% viscosity reduction of the heavy oil samples, which is 15% more than efficiency of adding the same concentration of toluene.The proposed diluent is a plant-based, non-hazardous substitute to the conventional hazardous diluents, e.g., xylene or toluene, that provides more efficient viscosity reduction compared to its conventional alternatives. Its flashpoint is higher than that of light crude resulting in less evaporation at high temperatures thus a longer period of reduced viscosity can be obtained. Furthermore, due to its high flashpoint, the proposed diluent can be employed in thermal methods more efficiently.
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