Main principles of the improved technique for the estimation of gas reserves in low-permeability Turonian sediments

The article describes the main principles of estimating volumetric parameters of gas onshore deposits in low-permeability reservoirs of the Turonian stage that were formed as a result of the long-term study of “supra-Cenomanian” sediments at the fields of Rosneft Oil Company PJSC, in particular, at the largest Kharampurskoye oil and gas condensate field. Based on a detailed analysis of the section, the authors formulated recommendations for optimal logging suite, well testing and analysis of the core taken from highly swellable clay rocks of the Kuznetsov formation.

Development of a Weighted Barite-Free Formate Drilling Mud for Well Construction under Complicated Conditions

Construction of oil and gas wells at offshore fields often involves high formation pressure and the presence of swellable clay rocks in the section. In addition, productivity preservation is also an important aspect. For this purpose, it is necessary to reduce the solids content of the drilling mud. The purpose of this work is to develop, improve, and study compositions of weighted drilling muds with low content of solids, on the basis of organic salts of alkali metals and polymers for the construction of wells prone to rock swelling and/or cavings, as well as drilling fluids for drilling-in the formation. In order to achieve the set goal the following is required: Analysis of existing drilling muds of higher density for drilling wells in unstable rock intervals and for drilling in the productive formation; analysis of experience in using drilling systems on the formic acid salts base and substantiation of requirements for flushing fluids during well construction; development and investigation of drilling mud compositions on the formate base; and the evaluation of inhibiting effect of systems containing organic salts, polymer reagents, and calcium carbonate on clay samples. The developed drilling mud is characterized by a high inhibiting ability that allows minimized mud-weighting by the natural solid phase. This reduces the volume of prepared mud and facilitates the regulation of its properties by reducing the dispersion of drilled cuttings; it eliminates problems related to hydration and the swelling of active clay rocks; and stabilizes unstable argillites prone to caving. The low solids content, low filtration rates, and inhibitory nature of the mud allows high stability of the rheological properties of the mud, and preserves oil and gas reservoir productivity under conditions of elevated formation pressure.

Anaerobic corrosion of carbon steel in compacted bentonite exposed to natural Opalinus clay porewater: Bentonite alteration study

Carbon steel is a potential canister material for the disposal of high-level radioactive waste in deep geological repositories in clays and clay rocks. Bentonite is considered as a potential backfill material for those multi-barrier systems. To predict the long-term performance and for safety assessment the knowledge of canister corrosion behavior is important. The corrosion products formed and mineralogically altered bentonite at the canister/bentonite interface can potentially provide an additional barrier against radionuclide migration. In-situ corrosion experiments were performed at the Mont Terri underground research laboratory. Coupons of carbon steel were embedded in Volclay MX-80 bentonite with controlled densities, installed in a borehole under simulated repository and anaerobic conditions and exposed to natural Opalinus clay porewater for a period up to 5.5 years (Smart et al., 2017). In the present study, the bentonite layer at the canister/bentonite interface was characterized by complementary microscopic and spectroscopic techniques (XPS, SEM-EDX, µXANES) under anoxic conditions. The interface revealed reddish-brown staining up to 2 mm depth into the bentonite in the zone adjacent to the steel in all three obtained samples. The XPS analysis revealed formation of sulfides at the interface consisting of iron and other trace metals present in the steel. The SEM-EDX analyses of the interface (embedded cross-cut with steel removed) showed different degrees of calcium enrichment in the bentonite adjacent to the metal for various samples. The µXRF analysis performed on the bentonite at the interface showed a scarce or distinct calcium-enriched rim up to 100 µm into the bentonite and iron-enriched rim depending on the sample (one sample in Fig. 1), while µXANES analysis revealed formation of iron silicate compounds in the reacted reddish-brown zone. The iron appears to displace calcium from the interlayer sites in montmorillonite. The calcium then precipitates at the interface as calcite. The extent of this process seems to be strongly related to the bentonite density. The steel coupon was removed prior to embedding, with the location marked as resin in Fig. 1. A line scan from the edge towards the bulk bentonite did not indicate any systematic gradient in the Fe2+/3+ ratio. The formation of mixed Fe2+/3+ silicate compounds appears to be heterogeneous. This work contributes to an increasing understanding of steel corrosion mechanisms in clay, which can improve the robustness of canister lifetime predictions.

Investigation of the Effect of Combined Binder Based on Portland Cement and Lime on the Properties of Non-Autoclave Silicate Materials Modified with Synthetic Crystalline Filler

Among the wide variety of currently used wall building materials and products, it is possible to single out the autoclave-hardened silicate products. To obtain silicate materials of autoclave hardening, lime-silica binders are mainly used. The hardening process of such a binder is carried out in an environment of water vapor at high temperature and pressure. It is relevant to use a certain type of silicate materials in the technology with raw materials that provide hardening with reduced parameters of hydrothermal synthesis, which will make it possible to obtain wall silicate materials in non-autoclave conditions. This can be done through the use of clay rocks of the mineral formation unfinished stage. In the course of the research, the effect of a combined binder based on Portland cement and lime on the properties of non-autoclave silicate materials modified with a synthetic crystalline filler was studied. It has been established that the addition of a synthetic crystalline filler represented by artificial calcium hydro-silicates makes it possible to increase the presence of a crystalline phase formed due to the clinker minerals hydration in the early stages of hardening, and, as a consequence, to increase the operational properties of the resulting composites. The addition of lime to the raw mixture will additionally compensate for the lack of calcium ions during the entire hardening process of non-autoclave silicate composites based on aluminosilicate raw materials and Portland cement.

Investigation of the Synthesized Calcium Hydrosilicates Effect on the Properties of Energy-Saving Wall Silicate Blocks Obtained on the Basis of Technogenic Raw Materials

Currently, building blocks are widely used in the construction industry, the use of which contributes to an increase in the speed of construction several times, and also reduces labor costs. To obtain wall blocks, various binders are currently used, but the use of composite binders obtained on the basis of new types of raw materials, is relevant. Among the currently non-used natural raw materials, it is possible to single out aluminosilicate rocks, unconventional for the construction industry, characterized by the presence of clay rocks of mineral formation unfinished stage (aggregates) in their composition. Based on the results of the studies carried out, the effect of the synthesized calcium hydrosilicates addition was established as СSH (I) and С2SH(A) on the properties of energy-saving wall silicate blocks obtained on the basis of technogenic aluminosilicate raw materials. The rational content of the СSH (I) additive is 1.5 wt. %, which contributes to an increase in the products’ strength by 30-50%. The optimum lime content in the raw mix is 12 wt. %. The nature of the influence С2SH(A) on the properties of non-autoclave silicate materials obtained by the method of injection technology, in general, coincides with the addition of CSH (I). The resulting material can be used as a structural material (non-supporting structures) inside low-rise buildings and structures. Low average density of this material (1300–1450 kg/m3) indicates the best thermal properties (the thermal conductivity coefficient of the samples is 0.17 W/m·K).

Baryshok. Enriching colour range of ceramic shapes on clay-based materials of low quality

Introduction. This article discusses the possibility of expanding the colour palette of a ceramic shard. Due to the shortage of high-quality clay raw materials for the manufacture of plastic molded facing bricks, the problem of manufacturing ceramic wall materials by semi-dry pressing from low-quality clay rocks is urgent.Materials and methods. The main raw material was non-caking clay raw material with a low content of clay and a high content of silt particles. Some corrective additives were used to expand the colour palette of ceramic bricks. In the article, the authors used both standard methods for determining the physical and mechanical properties and modern methods for studying the phase composition of materials.Results. The possibility of enriching the colour range of a ceramic shard based on non-sintered clay raw materials has been experimentally confirmed, provided that the mixture contains flux additives. When receiving products with a clarified shard, light-colored flutes should be used.Conclusion. The possibility of enriching the colour range of a ceramic cap by adding white-burning clay, introducing bleaching and chromophore additives and technogenic products has been established. Due to the differences in the chemical composition of clay raw materials from individual deposits, an individual approach to each of them is required.

Types of Void Space in the Bazhenov Reservoir Rocks

The deposits of the Bazhenov formation are a unique reservoir of unconventional oil reserves in Western Siberia. They contain both solid organic matter (kerogen) and liquid light oil. The successful development of these hydrocarbons is largely determined by the adequacy of the void space models. The aim of the study is to identify the types of void space in the sediments of the Bazhenov formation and to identify the distribution patterns across the section of the researched wells. The void space was studied by electron and optical microscopy, and the mineral composition of the rocks was determined by X-ray diffraction analysis. The deposits of the Bazhenov productive formation in the territory of Western Siberia are represented by a wide complex of lithotypes, including various kinds of silicites, carbonate, clay rocks, and mixtites. The reservoir space in the reservoir rocks of the Bazhenov formation is a complex and hierarchically subordinated system, which includes voids and fractures of various sizes, configurations, and genesis. The void space of the Bazhenov formation is characterized by a fairly high degree of spatial heterogeneity, which is controlled by lithological, facies, and tectonic factors, as well as the direction of catagenetic processes.