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One of the main problems during oil well completion and cementing operation is fluid migration through cement bulk or behind the cemented casing. Slurry composition and characteristic have been focused and improved in last decades to mitigate gas migration and, recently, aspects such as using nanotechnology have been investigated to amend the conditions. In this research, two moderate base slurries with 95 and 120 Pound per Cubic Feet (PCF) densities containing different percentages of nanosilica have been examined using a perfect test package. The results of Fluid Migration Analyzer (FMA) demonstrated that using correct percentage of nanosilica particles modified rheological behavior of the slurries and decreased fluid migration volume. Moreover, adding nanoparticles did not have any negative effects on any conventional parameters. However, static gel strength analyzer showed significant transient time reduction which is an important key in cement setting profile. Triaxial test results together with Mohr circles analyzing presented considerable progress in cement stability and compressive strength.

In petroleum industries, nanofluids have the potential to improve the characteristics of the fluids used in drilling wells or Enhanced Oil Recovery (EOR) processes. In this study, a water based mud containing polymer was considered as the base fluid. Different concentrations of TiO2 nanoparticle (0, 0.5 and 0.75 wt%) and different concentrations of KCl salt (0, 0.5, 1.5, and 3 wt%) were added to the base fluid and exposed to different temperatures (30, 50, 70 and 90 °C) with 19 different shear rates for investigating the effects of nanoparticle concentration, salt concentration, temperature and shear rate on viscosity of the base mud. Presence of TiO2 particles enhanced not only the rheological behavior but also electrical and thermal conductivity of fluid up to 25% and 43%, respectively. Furthermore, the stability of the fluid containing salt and nanoparticle was investigated in these temperatures owing to the fact that the temperature could cause degradation of the fluid. For the purpose of investigating this phenomenon, the after cooling experiment was conducted. In addition, the data gathered in this investigation were examined by using three famous rheological models (Power law, Herschel-Bulkley and Herschel-Bulkley-Papanastasiou models) and the rheological parameters of each model were determined.

Mineral scaling has been considered a great concern for developing the oil production from the underground petroleum reservoirs. One of the main causes of this phenomenon is known as the chemical incompatibility of injected brine, frequently sea water, with the reservoir brine leading to the deposition of various supersaturated salts such as calcium carbonate, calcium sulfate and barium sulfate. In present communication, an evolutionary approach namely, Gene Expression Programming (GEP), was employed for rigorous modeling of formation damage by mineral scaling of mixed sulfate salt deposition. At first, a large databank of damaged permeability datapoints as a function of injected volume, injection flowrate, temperature, differential pressure and ionic concentrations of the existing chemical species in the porous media was employed. In this regard, a user-friendly correlation was extended for the first time by the aforementioned technique in the literature. Professional evaluation of the suggested GEP-based model was implemented by different statistical parameters and appealing visualization tools. Having proposed the GEP-based correlation, statistical parameters of the Average Absolute Relative Deviation Percent (AARD%) of 0.640% and determination coefficient (R2) of 0.984 was calculated. Accordingly, it is demonstrated that the proposed model has a superior performance and great potential for efficient prediction of damaged permeability due to the mixed sulfate salt scaling. Moreover, the implemented outlier diagnosis technique verified the validity of the databank used for modeling, as well as the high robustness of the suggested model was confirmed. In conclusion, the developed correlation in this work can be of enormous practical value for skillful engineers and scientists in any academic study and industrial applications dealing with mixed salt deposition.

In the context of geological CO2 sequestration projects, CO2/water/rock wettability directly affects the capacities of residual and structural trapping mechanisms. Therefore, presenting an accurate model that can simulate the wettability behavior of CO2/water/rock under different environmental conditions is necessary. In this study, a new model based on adaptive neuro-fuzzy interference system (ANFIS) was developed for estimation of CO2/water/quartz contact angle as a function of influencing parameters, such as pressure, temperature, salinity, and salt type. Results of the proposed model were compared to the actual data and it was found that the presented model has immense potential with high correlation coefficient (R2) of 0.991 and average absolute relative error (AARE) of 2.010 for predicting the CO2/water/quartz contact angle. Finally, a sensitivity analysis was performed on the influencing factors. Results of this analysis demonstrated that salinity and pressure have the highest impact on the wettability of CO2/water/quartz. [ABSTRACT FROM AUTHOR]