The continuous development of global economy with decreasing in available hydrocarbon sources and increasing discovery and extraction costs due to decrease in-situ oil and gas reservoir, displays the necessity of using new techniques for the improve rate of penetration and productivity in well. Nanotechnology has already contributed significantly to technological advances in the energy industries. Nanotechnology has the potential to introduce revolutionary change in DRILLING industry. Nanotechnology produces nanomaterials with many attractive properties, which can play an important role in intensifying mud cake quality, reducing friction, eliminating differential pipe sticking, maintaining borehole stability, protecting reservoir, and enhancing oil and gas recovery. Nano FLUIDs can be designed by adding nano-sized particles in low volumetric fractions to a FLUID. The nano particles modify the FLUID properties, and suspensions of nano-sized particles can provide numerous advantages.This paper presents an extensive literature review of assessing the applications of nanomaterials in DRILLING and DRILLING FLUIDs, and evaluates the potential technical benefits that these nanomaterials might provide to petroleum development and production.

Background: Biodegradation of starch used in DRILLING FLUID by many microorganisms, results in reduction of starch concentration in the FLUID, which leads to FLUID efficiency downfall. The aim of present study was to identifythe major starch degrading bacteria in the DRILLING FLUID and manner of controling the growth and activity of these organisms.Methods: Bacteria present in back up DRILLING FLUID, were isolated and their amylase activity was studied by starch hydrolysis test. The strain with the most ability of starch hydrolysis in all three temperatures (37, 45 and 55oC) was selected as the superior strain and was identified by 16Sr RNA. Also growth curve of superior strain was plotted.Results: 54 bacterial strains include 26 Gram-positive Bacillus, 22 Gram-negative Bacillus and 6 Gram-positive Cocci were isolated. 18 strains from 26 Gram-positive Bacillus were spore forming bacteria. Three strains had growth in all three temperatures (37, 45 and 55oC) and showed significant amylase activity. Bacteria with the most mean of inhibition zone were selected as superior strains. The results of the 16Sr RNA analysis showed 99.8% similarity of superior strain to Bacillus licheniformis. The bacterium was in logarithmic phase at 8-48 hour after inoculation.Conclusion: Spore forming Gram-positive Bacillus belonging to Bacillus Genus like Bacillus licheniformis isolated in this study was the most active bacteria of degrading in well special conditions. Identification of degradation factors with the aim of selecting a suitable biocide is important to prevent the biodegradation.

A successful DRILLING operation depends strongly on a useful DRILLING FLUID system. Using nanoparticles (NP)s to formulate intelligent DRILLING FLUIDs gives them a wide range of optimal properties under different operating conditions and resolves any operational problems. In this study, in order to provide an effective solution for improving the rheological and high pressure/high temperature (HPHT) filtration properties of the oilbased DRILLING FLUID (OBDF), copper oxide (CuO) NPs were synthesized with dandelion morphology. CuO dandelions were characterized by using XRD, FTIR, SEM, and zeta potential measurements. A long time stabilized nanoFLUID (NF) was prepared and evaluated. The OBDF samples consisting of various amounts of NF ranging from 1 to 11% (V/V) were prepared. Then, the FLUID loss and rheological properties of OBDF were examined. The results showed that the OBDF containing 7% (V/V) NF was appropriate to improve the rheological properties such as yield point (YP), apparent viscosity (AV), and gel strength (GS). In addition, the minimum HPHT filtration value of 2 ml was acquired for the DRILLING FLUID containing 9% (V/V) NF. In conclusion, CuO NPs demonstrated a positive effect on the performance of the OBDF system.

In this study, using the results of performed shale formation Characterizatins and the history of DRILLING in Iranian oil fields, an environmentally friendly water based DRILLING FLUID is designed to replace the oil based DRILLING FLUIDs. This DRILLING FLUID has desirable properties in DRILLING water sensitive formations. New DRILLING FLUID additives including shale inhibitors, new polymers and sized solid particles have been used to prepare this new DRILLING FLUID. The most important properties of this new DRILLING FLUID are controlling the mud filtrate and pressure invasion to the formation, clay mineral alteration and activity reduction, improvement of the integrity of DRILLING cuttings, reduction in formation damage, stability at high temperatures, stability in acidity changes and the compatibility by DRILLING FLUIDs dilution during DRILLING operation. The lubricity and shale cuttings recovery of this new DRILLING FLUID are better than those of other similar water based DRILLING FLUIDs. Replacing this DRILLING FLUID by oil based DRILLING FLUIDs in DRILLING industry will be a great means to protect the environment and DRILLING personnel in addition to being economically advantageous.

Hydrogen sulfide is a very dangerous, toxic and corrosive gas. It can diffuse into DRILLING FLUID from formations during DRILLING of gas and oil wells. Hydrogen sulfide should be removed from this FLUID to reduce the environmental pollution, protect the health of DRILLING workers and prevent corrosion of pipelines and equipments. In this research nano zinc oxide with 14-25 nm particle size and 44-56 m2/g specific surface area was synthesized by spray pyrolysis method. The synthesized nanoparticles were used to remove hydrogen sulfide from water based DRILLING FLUID. The efficiency of these nanoparticles in the removal of hydrogen sulfide from DRILLING mud were evaluated and compared with that of bulk zinc oxide. The obtained results show that synthesized zinc oxide nanoparticles are completely able to remove hydrogen sulfide from water based DRILLING mud in just 15 min., whereas bulk zinc oxide is able to remove 2.5% of hydrogen sulfide in as long as 90 min. under the same operating conditions.

In this study, predictive capabilities of apparent viscosity of oil-based DRILLING FLUIDs which is used in National Iranian South Oilfields Company (NISOC) were evaluated using Newtonian and non-Newtonian models to drive a new suitable equation. The non-Newtonian models include Bingham plastic, Power law, Herschel-Bulkley, Casson, and Robertson-Stiff. To validate the results, the calculated viscosity from rheology models was compared to the fann 35 data of viscometer. The results showed that Robertson-Stiff model has the best prediction of shear stress and viscosity with an absolute average percent error of 3. 58. This was followed by Herschel-Bulkley, Casson, Power law, Bingham plastic, and Newtonian with the absolute average percent error of 3. 68, 3. 77, 9. 04, 20. 09, and 44. 02 respectively. Therefore, the new equation was proposed to predict the shear stress for oil-based DRILLING FLUIDs which is used in Southwestern Iranian Oilfields. In comparison to the results of the experimental data of this study, it was revealed that the proposed equation has a good agreement with the real shear stress and apparent viscosities.

The invert-emulsion DRILLING FLUIDs are commonly used to drill reactive formations because they inhibit water interaction with sensitive shales and dispersive formations. In an invert-emulsion DRILLING FLUID solid additives should not be wet. In the absence of oil wetting agents, solid particles including weighting agents and shale are usually preferentially water-wet in mineral oils/brine emulsions saturated with calcium chloride or sodium chloride. Phospholipid and alkylimidazoline were used to make the solids oil-wet. Then the wettability of Barite and Calcite in invert-emulsion was studied along with evaluation of yield point and gel strength of DRILLING FLUIDs. These oil- wetting agents caused Barite and Calcite to be moderately to strongly oil-wet resulting in lower yield point and gel strength for FLUID. Alkylimidazoline is the comparatively more effective oil-wetting agent in different invert-emulsion DRILLING FLUIDs.

An improved model of mud dispersion has been introduced in this work. The advantages of this model consist of a new analytical correlation for dispersivity by using resistivity log data and using a new aspect of capacitance dispersion model. Mathematical formulations were expressed, solved by numerical model taking advantage of actual log and formation data. Achieved results yielded reasonable values and trends which can be used to predict the DRILLING FLUID concentration near wellbore region and interpret the well log data. In comparison with the previous models (Civan and Engler, 1994; Donaldson and Chernoglazov, 1987), this model uses more reasonable data and assumptions making it closer to real conditions.

DRILLING FLUIDs are an essential component of the rotary DRILLING process used to drill for oil and gas on land and offshore environments. The injection of this nano particle into DRILLING FLUID increases the viscosity levels FLUIDs. In these experiments, the rheological properties of the FLUID including apparent viscosity (AV), plastic viscosity (PV), yielding point (YP), mud cake thickness and FLUID loss (FL) were studied before and after the addition of the nanoclay with different concentrations. In this study, nano particles of clay were used in order to enhance the rheological properties of DRILLING FLUIDs. The results showed nanoclay controls the FLUID loss and is resistant to high temperatures and also FLUID loss. We also found that nanoparticles varying in concentration (0.1 to 1 Wt %) and also size 1, 50 and 500 nm are shown to be effective at improving FLUID rheology.