Igor Shchurov
General Director of DTEK Neftegaz
Ivan Gafich
Director of Exploration and Prospective Development of DTEK Neftegaz
Based on the report of the 2nd Kiev Conference on Modern Methods of Drilling and Increasing Oil and Gas Production «Drilling. Intensification. Ecology and Labor Protection»
Ukraine today, more than ever, requires meaningful actions to build up the hydrocarbon resource potential (HC) and oil and gas production to meet its own needs and strengthen the country’s energy independence.
Positive changes in the legislative basis of subsoil use and the investment climate of recent years have led to a halt of the fall and a gradual increase in natural gas production. The most widespread activities were of «rapid success» - working with the existing wellsite stock: hydraulic fractures (HF) and intensification, capital repair and restoration work in the wellsites. However, the effect of these measures is observed, mainly, only in the short term.
Progress in drilling new wellsites, increasing resources and increasing hydrocarbon production in new promising areas has a slower pace. Despite the fact that the results of geological explorations (GE) and exploratory drilling at new promising sites would significantly increase hydrocarbon reserves and gas production volumes, they require time (on average, 5-7 years) and significant investments in conditions of high risk of capital. The latter is not contributed by current environment and existing investment climate today.
New «trendy» directions, such as shale gas, have not become widespread in Ukraine. If we do not talk about environmental issues, the main obstacles to their implementation by international players are the unstable political environment and the associated risks of capital. For Ukrainian companies, among other things, this is a significant amount of necessary investment, lack of technology and work experience. A significant increase in production is likely to be achieved from the objects such as tight gas, since such objects exist in most producing fields and significant undeveloped gas reserves are associated with them. At the same time, such work requires time, resources, appropriate technologies and the ability to apply them in specific geological conditions.
Thus, if we continue to move in an extensive way of development, we are doomed to constantly catch up with our state tasks in an attempt to become energetically independent and to cover oil and gas needs with our own production. Despite all attempts by domestic mining and service companies to proceed to an intensive type of development, the oil and gas business continues to develop predominantly in an extensive way. This approach does not meet the requirements of time and does not ensure a rapid increase in the rate of hydrocarbon production. The intensive way of development, first of all, provides for the wide use of more effective and perfect factors of production: modern technology, advanced technologies, scientific achievements, appropriate organization of production and professional development of specialists.
Are there any preconditions for increasing hydrocarbon production in Ukraine? Of course, as Ukraine has a significant resource potential and oil and gas reserves (Table 1). However, gas production in recent decades has decreased dramatically and does not exceed 18-19 bln of gas per year with the perspective of increasing to 24-25 bln by 2020, and the rate of extraction of explored reserves is much lower than in other European countries (Table 2). The question is how to ensure a rapid and sustainable increase in the production of hydrocarbons and, above all, natural gas. One of such ways is the rational development of the resource potential of existing fields. An example is the development of oil and gas assets of DTEK Neftegaz.
DTEK Neftegaz is developing two fields in the Poltava region. The Machukhi gas condensate field is a unique field in Ukraine. It is characterized by great depths, superhigh formation pressures and temperatures. This is a fractured reservoir. Exploratory drilling at this field began in the 1980s, but then none of the five drilled wellsited was brought into production. The Semirenki field is a traditional terrigenous reservoir. However, during the drilling operations it became obvious that the Semirenki is much more complicated than previously assumed by geologists. When drilling new wellsites water-carrying plots were identified in the center of the field, the sheet deposits turned into lenticular objects. DTEK Neftegaz has developed a complex approach to the development of the resource potential of these fields with the involvement of new technologies in geology, drilling, development of fields, optimization of the wellsite stock and intensification of production, in infrastructure projects and the introduction of IT technologies in all areas of production activities (Fig. 1).
At the first stage, a detailed geological study of the objects was carried out. It included a wide-azimuth seismic survey, which was specially designed, based on the geology of the objects, the features of the hydrocarbon deposit structure, on the understanding of the tasks that needed to be solved for efficient development of reservoirs (Fig. 2).
To further develop the reserves and resource potential of existing hydrocarbon fields, new approaches to modeling their geological structure and development processes were required. Namely, the creation of permanent geological and technological models (PGTM) of fields with interactive databases that are generated in real time by the algorithm of the sheet-wellsite-field-objects of the ground infrastructure-pipeline. Application of this approach allowed to optimize the processes of drainage of hydrocarbon reserves, work of the wellsite stock and to increase the volumes of gas production without drilling additional wellsites. Field models have become a tool for making managerial decisions regarding drilling, production optimization, and infrastructure facilities.
Today, the growth of the resource potential is especially important for Ukrainian gas producers. The growth of reserves is the basis for future development, without which it is difficult to maintain the production rates and increase them. In Ukraine, at the moment, the number of licensed sites is limited, the amount of hard-to-reach reserves is increasing. Therefore, it is important to look for new promising sites. New geological exploration technologies used at the Makuchi oil field of DTEK Neftegaz made it possible to identify a number of non-traditional search objects: river beds, riverside and avandelta sandbodies (Fig. 4). Some of them are confirmed by exploratory wellsites, which their edge parts have been opened with. These are quite large resources for a small license area of 18 km2. The additional exploration of the Semirenki field showed that there are promising zones around it that are associated with the deep-lying leyers of the Carbon and Devonian, as well as a number of new objects of stratigraphic and lithofacies character in the marginal parts of the field. These are complex objects that are very difficult to identify by geological exploration. Given the great depths of their occurrence, the risks of exploratory drilling remain high. However, the probabilistic estimates of the resource potential of such facilities exceed 20 bln m3 of gas. Therefore, DTEK Neftegaz faces the task of increasing the validity of forecasts and geological models of perspective objects, using a complex approach to study them and new technologies for processing geological and geophysical information.
More than two years ago, DTEK Neftegaz drilled and placed on production the deepest productive wellsite in Europe - wellsite #17 of the Semirenki field, from which an industrial gas inflow was obtained at a depth of 6750 m. Earlier, many experts claimed that at such a depth there can not be a reservoir. However, now, according to scientists, at such depths, half of the resource potential of the main producing region of the country is concentrated (Fig. 5). As a result of complex geological and geophysical studies, which included wide-azimuth 3D seismic survey, core sampling and research, industrial geophysical work and deep drilling data analysis, more than 2 bln m3 of reserves and more than 4 bln m3 of C2 gas were built up in this wellsite. Based on the obtained results and the analysis of other similar facilities, we can talk about the discovery of new hydrocarbon deposits under the existing fields in the axile part of the Dnieper-Donets Basin with economically profitable gas reserves that are commensurate in volume with the main objects of operation, as with the case of other oil and gas regions of the world. Thus, the drilling of deep wellsites also allows to increase the resource potential of the fields.
To the research and development of production programs for DTEK Neftegaz were attracted both Ukrainian and foreign scientific institutions, private experts, world-class organizations that have experience with such facilities. For example, taking into account the great depths (5.5 - 6.5 km) and the secondary nature of the reservoirs, it is important to study the void space and the decompactification of formations as reservoirs of natural gas accumulations. In domestic laboratories and foreign research centers, complex studies of the void space of fracture-porous reservoirs on core (computer tomography, investigation of filtration properties and pathways of formation fluids in conditions close to reservoir-type with modeling of mountain pressures) are conducted. Along with the traditional, advanced technologies of anisotropy analysis of rock massives (RS-360, 5D, DWM) were used to predict fracture systems and their azimuthal development. Special high-tech investigations of wellsite sections (FMI, CXD, MPD, etc.) were carried out.
It was important at the Machukhi field to understand the structural features of the reservoir and the conductivity of the faults, the development of cracks in the carbonate massif, since the production rate of the wellsites is mainly formed by fractured intervals. To solve this problem, a geological exploration, wellsite research, geological and geophysical data processing and integration of results was created and implemented, so that high-tech companies from Great Britain, Canada and the USA, Ukrainian and European research institutes and organizations were attracted to it. As a result, the anisotropy predictions were obtained for the properties of the rock massif, the systems for the development of fractures in them and their azimuthal distribution, that is, the channels along which the formation fluids travel are predicted. This allowed to reduce drilling volumes and optimize the location of wellsites.
The implementation of geological exploration programs and exploratory drilling requires significant investment costs. Optimization of drilling programs and processes of development of fields allows to reduce the volume of investments, and part of the released funds to be directed to the introduction of new technologies and geological exploration. So, the application of such a complex approach allowed to optimize the development program of the Machukhi field, reducing drilling volumes from 8 to 4 wellsites with a depth of 6,000 m, while maintaining the pace and volumes of gas production. This has reduced the volume of investments in the development of the field, which is estimated at approximately $ 80 million.
Optimization of the program of drilling, construction and operation of ground infrastructure facilities of the Semirenki field also allowed to reduce by one third the investments in development of the field. Based on the optimization results, 25 wellsites instead of 41, as previously projected, are enough for efficient and economically profitable extraction of the field’s reserves. At the same time, the use of reservoir parameters technologies in combination with new approaches to drilling technology, the arrangement of wellsites and their development, allowed them to significantly (by 30-40%) increase their average production rate.
Applying the abovementioned approaches to the rational use of mineral resources allowed the company to increase its annual production volumes from the great depths by 3 times in 3 years, reaching a production level of 1.655 bln m3 of gas and about 55,000 tons of condensate in 2017, to open and explore a number of new promising sites, the resource potential of which is estimated at 17 bln m3 of gas. According to the results of geological exploration and prospecting drilling, 3 bln m3 of gas reserves have been built up, and the resource potential of existing facilities has been increased by 2.4 times.
The achieved rates of development of the main operating objects are 10-16% of their current reserves and will be increased after the completion of the drilling program in 2018-2019 of nine new wellsites with depths of 5.5-6.2 km at the level of 16-19%. It should be noted that for the gas industry of the state as a whole, this index does not exceed 5-10%.
Experience of DTEK Neftegaz shows that in Ukraine there is a significant resource potential at selected operational oil and gas production sites, a rational approach to identifying and developing which, in conjunction with modern technologies of exploration and development, will allow to increase gas and oil production in the short term, without a significant increase in investment costs in comparison with traditional methods of geological exploration and mining activities.
DTEK Neftegaz is open for cooperation, exchange of results of application of modern technologies at the sites for which we have accumulated the necessary examination and experience.
REFERENCES
1. Aleksey Lukin, Hydrocarbon potential of large depths and perspectives for its development in Ukraine. The Geofizicheskiy Zhurnal journal, 2014, vol. 36, pp. 3 - 23.
2. https://www.geoilandgas.com/our-voice/21st-century-innovation-requires-new-approach
3. https://economics.unian.ua/industry/2358458-ukrajina-volodie-velicheznimi-resursami-gazu-ekspert-nazvav-tsifru-v-mayje-6-trilyoniv-kubiv.html
4. https://economics.unian.ua/energetics/2343367-rozvidanih-zapasiv-gazu-v-ukrajini-vistachit-na-22-roki-vidobutku.html
