Comparing the results of lineament analysis with isotope geochemistry data

This article presents the results of a geochemical survey carried out in the southwestern part of the Siberian platform, within the Sayan-Yenisei (Angara) syneclise (a superorder Riphean-Middle Paleozoic structure). The object of research was hydrocarbon gases contained in the subsoil rocks (clays). The subsoil samples were taken from the bottom of boreholes (40 mm in diameter) made with an electric drill. The sampling depth was 0.6–1 m. Further laboratory studies included chromatographic and isotope analysis. Lineament analysis of the digital elevation model was carried out as a complementary study. One of the lineament analysis results was a lineament density map, which reflects the permeability (macro-fracture density) of the sedimentary cover. This allowed a comparison of the macro-fracture density with the gas content and isotopic composition. The study revealed that gases with a high content of heavy isotopes tend to gather in the low permeability areas. This can be explained by the fact that the gases disperse quickly within fractured zones, and deep gases should be expected only in the areas with strong cap rocks, i.e. in the areas with low macrofracture density where stable hydrocarbon deposits have already formed. Keywords: hydrocarbons; geochemical survey; isotope geochemistry; lineament analysis.

Controlled Production of Natural Gas Hydrates in an Experimental Device with an Internal Circulation Circuit

For countries with limited access to conventional hydrocarbon gases, methane hydrates have emerged as a potential energy source. In view of the European Union’s requirements to reduce the energy intensity of technological processes and increase energy security, it appears promising to accumulate natural gas and biomethane in the form of hydrate structures and release them if necessary. Storing gas in this form in an energy-efficient manner creates interest in developing and innovating technologies in this area. Hydrates that form in gas pipelines are generated by a more or less random process and are an undesirable phenomenon in gas transportation. In our case, the process implemented in the proposed experimental device is a controlled process, which can generate hydrates in orders of magnitude shorter times compared to the classical methods of generating natural gas hydrates in autoclaves by saturating water only. The recirculation of gas-saturated water has been shown to be the most significant factor in reducing the energy consumption of natural gas hydrate generation. Not only is the energy intensity of generation reduced, but also its generation time. In this paper, a circuit diagram for an experimental device for natural gas hydrate generation is shown with complete description, principle of operation, and measurement methodology. The natural gas hydrate formation process is analyzed using a mathematical model that correlates well with the measured hydrate formation times. Hydrates may become a current challenge in the future and, once verified, may find applications in various fields of technology or industry.

An investigation of methods for calculating the volume of methane dissolved in reservoir water

Existing gas production technologies limit gas recovery at the level of 85 %. Therefore, it is important to introduce technologies that make it possible to maximize the volume of production and intensify the inflow; for their selection it is important to have a reliable estimate of the residual gas reserves, since with a significant volume of the aquifer of gas fields, the volume of dissolved gas can be up to 10 % of the total reserves of the reservoir, which should be taken into account when designing the application of technologies to increase gas recovery.The main hydrocarbon dissolving in reservoir water is methane. In this regard, it is of interest to study methods that make it possible to determine the volume of hydrocarbon gases dissolved in saline water, which will make it possible to determine the total reserves of such gas. We investigated the existing methods for calculating the amount of methane dissolved in reservoir water, and gave a quantitative assessment of the volume of gas dissolved in water.

Features of the composition of gas sorbed in the rocks of the upper part of the sedimentary cover section

The topicality of the article is determined by the insufficient reliability of geochemical oil and gas exploration data for the localization of petroliferous geological objects. Geochemical surveys are carried out to mapping hydrocarbon anomalies caused by vertical migration of fluid from hydrocarbon deposits. Practice shows that not all anomalies in the content of hydrocarbons in the near-surface environment are related to the oil-bearing capacity of a given subsoil area. Therefore, when interpreting the data of geochemical oil and gas prospecting surveys, it is necessary to take into account not only quantitative indicators (namely, content of hydrocarbon gases on the surface), but also the composition of the gas sorbed by the near-surface substrate. The purpose of the article is to determine the composition of the dissipated gases in the rocks of the upper part of the section, to reveal the inter-component relationships, and, on this basis, to determine the genesis of each gas component sorbed by the rocks of the upper part of the section. To solve this problem, statistical processing of data on the component content of gas from core degassing of shallow (up to 30 m) wells drilled in the petroliferous territory of the north of Western Siberia was carried out. The obtained results confirmed the genetic heterogeneity of dissipated hydrocarbons and inorganic gases in the upper part of the sedimentary cover.

Core Effective and Relative Permeability Measurements for Conventional and Unconventional Reservoirs by Saturation Monitoring in High Frequency 3d Gradient NMR

A big challenge in tight conventional and unconventional rock systems is the lack of representative reservoir deliverability models for movement of water, oil and gas through micro-pore and nano-pore networks. Relative permeability is a key input in modelling these rocks; but due to limitations in core analysis techniques, permeability has become a knob or tuning parameter in reservoir simulation. Current relative permeability measurements on conventional core samples rely on density contrast between oil/water or gas/water on CT (Computed Tomography) scans and recording of effluent volumes to determine relative fluid saturations during the core flooding process. However, tight rocks are characterized by low porosities (< 10 %) and ultra-low permeabilities (< 1 micro-Darcy), that make effective and relative permeability measurements very difficult, time-consuming, and prone to high errors associated with low pore volumes and flow rates. Nuclear Magnetic Resonance (NMR) measurements have been used extensively in the industry to measure fluid porosities, pore size characterization, wettability evaluation, etc. Core NMR scans can provide accurate quantification of pore fluids (oil, gas, water) even in very small quantities, using T2, T1T2 and D-T2 activation sequences. We have developed a novel process to perform experiments that measure effective and relative permeability values on both conventional and tight reservoirs at reservoir conditions while accurately monitoring fluid saturations and fluid fronts in a 12 MHz 3D gradient NMR spectrometer. The experimental process starts by acquiring Micro-CT scans of the cylindrical rock plugs to screen the samples for artifacts or microcracks that may affect permeability measurements. Once the samples are chosen, NMR T2 and T1T2 scans are performed to establish residual fluid saturations in the as-received state. If a liquid effective permeability test is required, the samples are then saturated with the given liquid through a combination of humidification, vacuum-assisted spontaneous imbibition, and saturation under pressure and temperature. After saturation, NMR scans are obtained to verify the volumes of the liquids and determine if the samples have achieved complete saturation. The sample is then loaded into a special core-flooding vessel that is invisible to the NMR spectrometer to minimize interference with the NMR signals from the fluids in the sample. The sample is brought up to reservoir stress and temperature, and the main flowing fluid is injected from one side of the sample while controlling the pressures on the other side of the sample with a back pressure regulator. The saturation front of the injected fluid is continuously monitored using 2D and 3D gradient NMR scans and the volumes of different fluids in the sample are measured using NMR T2 and T1T2 scans. The use of a 12 MHz NMR spectrometer provides very high SNR (signal-to-noise ratio); and clear distinction of water and hydrocarbon signals in the core plug during the entire process. The scanning times are also reduced by orders of magnitude, thereby allowing for more scans to properly capture the saturation front and changes in saturation. Simultaneously, the fluid flowrates and pressures are recorded in order to compute permeability values. The setup is rated to 10,000 psi confining pressures, 9000 psi of pore pressure and a working temperature of up to 100 C. Flowrates as low as 0.00001 cc/min can be recorded. These tests have been done with brine, dead and live crudes, and hydrocarbon gases. The measured relative permeability values have been used successfully in both simulation and production modelling studies in various reservoirs worldwide.

Reservoir Engineering and Geomechanical Aspects of Well Plugging and Abandonment

With the maturation of many oilfields, further well abandonments will occur in the years to come. There are issues about improper well abandonment that can have far-reaching effects for responsible companies or entities. At this time in the US, where most of the operation is operated by non-government entities, sometimes the sovereign state may end up covering the cost of well abandonment when the operator is not financially capable in managing such costs. That will be a burden to the public taxpayers. In this paper, we review an important aspect of the well abandonment practices and at present, based on a reservoir modeling approach, more clearance on the potential formation of free gas that can be a cause of concern. We also discuss the integrity issues of the sealing process. We point out how the development of cracks caused by many factors, including geomechanical effects or slow deterioration of the cement seal, in the long run, may result in generating escape paths for the evolved hydrocarbon gases.

Commercialization of Al Reyadah – World's 1st Carbon Capture CCUS Project from Iron & Steel Industry for Enhanced Oil Recovery CO2-EOR

As fossil fuels will continue to be a key source of energy for the world, the role of carbon capture utilization and storage (CCUS) has become increasingly important in addressing climate change by limiting emissions and by establishing a pathway to reaching net-zero. In spite of its significance, the deployment of CCUS globally in the past decade has not met expectations. It is largely due to the challenges in commercializing the technology. On the contrary, ADNOC successfully deployed CCUS in 2016 and has been operating Al Reyadah - the world's first CCUS project in Iron & Steel Industry and Middle East's first commercial CCUS project for enhanced oil recovery (CO2-EOR). Similar to other industrialized economies, Abu Dhabi has various sources where carbon dioxide (CO2) is emitted. It also has an advanced oil & gas industry which requires CO2 for enhanced oil recovery (EOR) in order to improve production output. ADNOC synergized these two industries to create a business case. The concept of a CO2 network, linking CO2 producer (source) and CO2 user for EOR (sinks) was developed as far back as 2008. Various studies where undertaken and a steel facility was identified as an ideal choice for a 1st project, given availability of CO2 and proximity to the ADNOC oil fields. In 2012, Al Reyadah was formed to develop the facility and pipeline that is operating today. This is the first step in a vision that would see multiple sources within Abu Dhabi that will be connected via a pipeline network to supply the CO2 needs of ADNOC for EOR, sequestering CO2 and reducing the UAEs greenhouse footprint, whilst freeing up vital hydrocarbon gases (used currently in EOR) for use in commercial industry. From inception, Al Reyadah has been referenced for decarbonization by many global organizations including International Energy Agency (IEA) and International Renewable Energy Agency (IRENA) and has won prestigious recognitions from Carbon Sequestration Leadership Forum (CSLF) and Emirates Energy Awards (EEA). This paper discusses the various strategies and commercialization tactics that ADNOC applied to deploy this unique project, which is only among 21 CCS/CCUS projects operating in the world in 2020 and a precursor to thousands of CCS/CCUS projects that are expected to be built globally in the coming years.

Results of reinterpretation of marine geochemical survey on the Sakhalin shelf

Geochemical survey of hydrocarbons (HC) all over the world is a reliable tool of the complex of geological exploration, which allows to localize hydrocarbon saturation in structures exposed by seismic exploration, as well as to identify non-structural deposits. In 2011, a marine geochemical survey of the sorbed gases of bottom sediments was carried out on the shelf section of the northwest of Sakhalin Island. Based on the results of geochemical studies, 12 maps of the distribution of hydrocarbon and non-hydrocarbon gases in the work area and 7 maps of the distribution of metals in bottom sediments were constructed. Promising areas were distinguished by anomalies with the maximum content of parameters. The research area is characterized by a complex structure, located within the Baikal synclinal zone of the North Sakhalin oil and gas basin, which is part of the rift system of the Cenozoic sedimentary basins the Sea of Okhotsk. In 2019, the authors began to re-process and reinterpret the data in order to clarify the results. The work was based on modern theoretical foundations and methodological approaches of oil and gas prospecting geochemistry. The interpretation of the results was carried out on the basis of the model of interpretation of geochemical anomalies developed by the authors. Maps of anomalies were constructed according to 11 geochemical criteria and two geological and geochemical sections. The complex interpretation of geological and geochemical data was carried out taking into account the results of seismic exploration and drilling in a single project. According to the results of the complex interpretation, 6 promising sites were identified, which are ranked according to the degree of prospects.