Kazakhstan journal for oil & gas industry

This article discusses the results of a study of the geologic structure of Mesozoic sediments in the Kazakhstan sector of the Caspian Sea South Mangyshlak sedimentary basin. This paper includes an analysis of existing geological and geophysical data aimed at describing the characteristics of petroleum system elements. The main features of the sedimentation conditions of oil source rocks, reservoirs, and caps have been analyzed. The key hydrocarbon source zones in the territory of the Kazakhstan sector of the Caspian Sea have been determined. The correlation of existing wells to determine regional covers and main trends in reservoir sedimentation has been provided.

Porosity, absolute permeability and diffusion coefficient are important characteristics of the flow of fluids in the pore space of rocks, the determination of which is resource-intensive and time-consuming. With the development of deep machine learning methods over the past 3–4 years, artificial neural networks have begun to be actively used in determining the transport properties of the “liquid-porous medium” system and the geometric characteristics of the pore space of samples based on their images. This method allows you to quickly determine the desired properties with acceptable accuracy. Therefore, the question arises about the effectiveness and adequacy of deep machine learning methods for these purposes.

This article provides a scientific review of open literature sources on the determination of absolute permeability, diffusion coefficient and porosity from images obtained by different scanning methods. We also used our own data, namely images for 4 carbonate samples, and presented the results of predicting the connected porosity of these samples based on their X-ray images using the convolutional neural network model we built.

The review showed that images of rock samples obtained using various scanning methods make it possible to calculate their transport properties with high reliability in a significantly short time. This means that deep machine learning can be a good alternative tool for calculating the properties of rock samples based on their images. The model we built showed the predictive ability of the porosity of 3 carbonate samples with a reliability coefficient of 0.936–0.976.

Oil production from fields with hard-to-recover reserves always remains a challenge for the oil and gas industry, mainly due to one special factor – the high viscosity of oil, which implies low mobility of oil in a porous medium. Over time, traditional methods of increasing oil recovery become less effective due to a decrease in readily available oil reserves and the complexity of geological conditions for field development. In this regard, the need to use innovative methods to increase oil recovery is becoming more urgent. In recent decades, research in this area has shown significant progress, various methods have been introduced to reduce the viscosity of oil. One of the most effective and actively developing approaches in this area is thermal methods of enhanced oil recovery. They are based on the injection of thermal energy into the reservoir in order to reduce the viscosity of oil and, consequently, increase mobility, which in turn will greatly facilitate the displacement of oil from the rock to the surface.

Despite certain successes achieved in the use of various methods of increasing oil recovery in the production of heavy oil, the problem of finding alternative methods remains relevant.

This article presents the review of alternative methods of enhanced oil recovery, including principle of operation of electromagnetic heating of the reservoir, the influence and effectiveness of radio waves and microwave frequencies on the reservoir and the properties of oil, ultrasonic exposure, advantages and disadvantages of alternative methods, comparing them with traditional methods, analyzing the productivity of fields where alternative methods of enhanced oil recovery were used.

Oftentimes oil and gas wells can be affected to various technological as well as chemical and natural stresses. Perforations, fracturing, side tracking from under the casings shoe, formation integrity testings all these lead to the cement sheath fragility and the annulus integrity deterioration causing the emergence of net of cracks in the cement sheath, which contribute to nascence of behind-the-casing flows.

World statistics say that the issues of casing string-borehole annulus unsealing prevention, as well as the effective restoration of the cement sheath integrity in the presence of a wide range of water-shutoff materials and technologies for inflows bounding, do still remain open and require non-standard solutions. In this connection, the development of “self-healing” plugging material, which allows the cement stone to independently regenerate its integrity, thereby excluding technological shutdowns and the intervention of repair equipment, is one of the highest priority tasks and promising methods for eliminating behind-the-casing flows, accompanied by restoring the integrity of the well cement sheath. An advanced alternative to the traditional plugging material is elaboration of "self-healing" cements, which is hopeful in the line of the above-mentioned peculiarities.

Background: The rock and geological section of the Urikhtau oil and gas condensate field is a complex geological system, including a variety of rocks of different densities and angles of occurrence, as well as disjunctive faults, which in turn complicates the process of designing and constructing wells. This article discusses the experience of geological and geomechanical modeling at this field.

Aim: The purpose of this work is to consider geological and geomechanical modeling at the Urikhtau oil and gas condensate field as a method for further application in the design of well construction, taking into account the complexity of the geological structure of the field.

Materials and methods: To build a 3D model, data from seismic and geophysical surveys were used, as well as historical data to correlate calculations.

Results: The result of the modeling is the development of recommendations for the well profile, its design and optimal values of drilling fluid density, which will create a safe “drillability window” for well construction.

Conclusion: Geological and geomechanical modeling allowed us to develop key recommendations for well design, including optimizing drilling fluid density and ensuring wellbore stability.

In oil and gas production, treatment and transportation technologies, gas hydrates cause serious problems associated with disruption of these technological processes. The traditional and most common method of combating gas hydrates in the oil and gas industry is the use of methanol as a hydrate inhibitor. The specific consumption indicators of methanol consumption as an inhibitor of the formation of gas hydrates directly depend on the composition of the extracted products, as well as on the technology for preparing the extracted products for transportation.

Gas hydrates represent one of the major economic and safety problems in the oil and gas industry in the exploration, production, processing and transportation of gas and hydrocarbons.

This article analyzes modern methods for methanol regeneration at oil and gas industry enterprises, and describes in detail the methods and parameters of processing plants that are used for the regeneration of water-methanol solutions. The advantages and disadvantages of advanced methods of water-methanol solutions regeneration are described. As a result of the review of existing technologies, the distillation method was determined to be the most preferable, as the most proven and widely used method today.

Background: The conservation of valuable bacterial strains is crucial for various scientific, industrial, and environmental applications. Microorganisms with oil-emulsifying and oil-displacing properties are potentially significant for biotechnologies applied in the oil industry, particularly in such areas as bioremediation and tertiary enhanced oil recovery. To supply enterprises with pure cultures of microorganisms, they should be constantly maintained in the collection conditions in an active state while monitoring the preservation of their biotechnological properties. Therefore, keeping microorganism strains in working conditions and preserving their valuable properties are important for almost any work with microorganisms, ranging from primary research to their use in the production of various biopreparations.

Aim: The article focuses on studying a method for preserving bacteria that are useful in the oil industry. This method involves modifying the technique of microencapsulating microorganism cells in alginate gel by adding glycerin, which is used as an agent with biostatic action.

Materials and methods: The subject of research are eight hydrocarbon-oxidizing cultures of microorganisms that were sourced from the Department of Biotechnology of the al-Farabi Kazakh National University. Of these, four cultures were spore-bearing, while the other four were non-spore-bearing. The research employed microbiological methods of cultivation and storage of microorganisms in both solid and liquid media under aerobic conditions. In addition, Cooper's method was used to determine oil emulsification index and statistical methods for data analysis.

Results: It has been found that adding glycerin (15% vol.) as a biostatic to the gel-forming matrix of sodium alginate can ensure long-term (up to 6 months) cell viability for the studied bacteria in the range of 88-96% while maintaining functionality of immobilized cells. The values of the bacteria’s oil emulsification remained at the pre-conservation levels, whereas traditional storage methods result in a lower number of viable cells after six months. It should be noted that after six months of being stored in encapsulated form with glycerin, the viability of non-sporе-forming Pseudomonas cultures is lower (88-91%) than spore-forming Bacillus (95-98%). This correlation is also is observed for traditional methods.

Conclusion: The modern method of preserving bacteria allows for their long-term storage while maintaining functionality and viability.