International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

Since 90% of all problems related to the wellbore instability occur during drilling through shales, which are mostly consisted of clay minerals, the filtrate from drilling mud penetrate into shale rocks and lead to their destabilization, so the industry is considering the possible application of new types of additives because conventional additives, due to their size, cannot enter in pores of shales, plug them and reduce further filtrate penetration. The oil industry in last few years turns to investigate possible application of nanoparticles because they can enter in small shale pores and plug them, thus increasing the wellbore stability. In this paper the influence of the size (50 nm and between 20 and 30 nm) and concentration (0.5, 1, 3 and 5 wt%) of Fe2O3 nanoparticles on density, rheology, API filtration, and swelling of laboratory prepared pellets in contact with mud without and with nanoparticles was determined. Due to the fact that the rheological properties are significantly increased at higher concentrations, and that smaller particles give better results with an emphasis on increasing the wellbore stability further tests should be carried out with nanoparticles Fe2O3 which size is between 20 and 30 nm in maximum concentration of 1 wt%.

The use of biodegradable waste is interesting for many companies from different industries, and in the last few years, more detailed research about its usefulness in the oil and gas industry, specifically as potential additives for the preparation of water-based drilling mud, has begun. Given that this type of research is globally important, there are data on the use of different types of food waste for this purpose, and scientists have mainly researched the biodegradable waste that is generated in larger quantities in a certain part of the world. Among the different types of waste whose effect has been investigated through laboratory measurements of various properties essential for drilling mud, there is also some data on egg shell. In this article, detalied set of data shows how egg shell affects the filtration properties of the drilling mud, the rheological properties, as well as the swelling reduction of the clay component of the rock when it is in contact with drilling mud with added egg shell in its composition.

During mud circulation pressure losses occur in all sections of the wellbore: surface pipeline, inside drill string, drill bit and around drill string. The sum of the pressure losses calculated for each section is equal to the total pressure loss in the system, i.e. the pressure that is read on the manometer of the mud pump. The mud flow through annulus (between drill pipes/collars and open hole/casing) causes an increased pressure loss for the certain flow rate which increases the pressure exerted on the wellbore wall, so it is important to manage it. In this paper, the influence of SiO2 nanoparticles on the rheological properties of bentonite mud was examined. After tha t, for a typical wellbore construction and selected mud flow was calculated their influence on pressure losses in the area around drilling pipes and collars. The pressure losses were determined using the Bingham model which provides an easy way to obtain data of acceptable accuracy for the case of application in conventional vertical wells. The results indicate that the addition of SiO2 nanoparticles can reduce the pressure loss during mud circulation, in some cases by more than 50%.

Casing is an extremely important element in the process of drilling a well borehole, as they define the diameter of the well and, among many other tasks, protect it from collapsing. In order to ensure long-term successful performance of all tasks, it is necessary to appropriately dimension casing, which means that the appropriate inner and outer diameter should be selected with the appropriate material and its quality, with proper installation depth for each set of casing. Conventional casing made of steel is most often used and this is still an ideal material for most wells. However, this material is prone to corrosion, which is a major problem on certain locations du ring the
production life of the well. Reduction and possibly elimination of corrosion on casing led the industry to explore financially viable composite materials, such as fiberglass, that could withstand expected stresses in well conditions with better corrosion resistance th an steel.