Changes of deformational and reservoir properties of arenaceous-argillaceous rocks due to operation of underground gas storage facilities

This paper discusses issues of the decline of the reservoir properties of arenaceous-argillaceous rocks as a result of declining porosity due to long-term operation of underground gas storage facilities. An analysis of the many-year operation of storage facilities, as well as calculation, has revealed that the active capacity of a storage reservoir gradually decreases under certain conditions of underground storage operations. We performed a series of experiments with model specimens in order to support the hypothesis of decreasing reservoir (capacity-filtration) properties because of changes in the value and structure of the pore space. These experiments showed that the cyclic loading and unloading of arenaceous-silty rocks during long-term operation of underground gas storage facilities can significantly decrease the reservoir parameters of reservoirs created within worked out gas-and-gas condensate fields. Laboratory studies of model specimens corresponding to feldspar sandstone in their composition, porosity, and strength proved that porosity considerably decreases in such reservoirs at actually existing values of formation pressure. Tests of sand performed under conditions close to those existing during the development of hydrocarbon fields also showed that their permeability gradually decreases in the process of cyclic changes of effective pressure.     

Memory Effects in Rock Salt Under Triaxial Stress State and Their Use for Stress Measurement in a Rock Mass

Summary Regularities of memory effects in rock salt specimens under triaxial stress state were investigated. Each specimen was subjected to two loading cycles. The first cycle was axisymmetric triaxial compression (σ₁ >σ₂=σ₃). The second cycle was uniaxial compression in the direction of σ₁ of the first cycle. Distinct acoustic emission (AE) and deformation memory effects were observed in the second cycle at the stress value equal to a linear combination of the first cycle principal stresses given by σ₁− (k + 1) σ₃, where k is about 0.5–0.6 for rock salt. Anomalies in deformation curves were found to be more reliable than the AE methods in distinguishing memory symptoms. The necessary pre-requisite for memory formation in the first cycle was that σ₁ exceeded the elastic limit, corresponding to the given confining stress σ₃. Inflections in uniaxial stress versus axial strain and lateral strain curves, in the second cycle, were observed at equal stress values if in the first cycle σ₁ exceeded the elastic limit and memory-forming damage was induced. If there was no memory-forming damage, those inflections were seen at different stress values. This characteristic was used to distinguish between true memory effects and natural characteristic points in deformation curves derived from rock salt testing. A new memory symptom was established, namely a turn point in curve “uniaxial stress versus differential coefficient of lateral strains”. The results form a basis for application of the memory effects for stress measurement in rock salt masses.     

Mineralogical and geochemical characteristics and predicted reserves of gold-base metal ore mineralization in southern Armenia and northwestern Iran

This paper reports newly obtained data on the mineralogy, geochemistry, and predicted reserves of the Shaumyan gold-base metal deposit in southern Armenia and the Kharvana occurrence of ore mineralization in northwestern Iran. Original Russian Text ? A.A. Matveev, E.M. Spiridonov, S.V. Grigoryan, S.Kh. Tabatabaei, S. V. Filimonov, 2006, published in Geokhimiya, 2006, No. 8, pp. 879–890.     

Research of thermal processes in the soil during the development of oil fields in the Far North by the compression method with heating

In this paper, the hazard of adverse heat effect on permafrost soil as a result of viscous oil production in the Far North is studied with the method of thermocompression supply of superheated water steam to the oil-bearing layer. It is found that, due to the divergent nature of heat transfer and convective complex movement of air in the space between the tubing and the casing, the temperature of the latter in the area of load-bearing elements heated to 130°C is about 70°C. The heterogeneity of the temperature field is leveled up to 4–5% at a distance of 400–420 mm from the axis of the tubing. The thickness of the melting layer of ground ice within 90 days of operation of the tubing depends on the percentage of water-filled pores in the soil. With the minimum (10%) percentage of water-filled pores in the soil layer, the thickness of the ground ice melting layer for 90 days of operation of the tubing does not exceed 2.6 m.     

Chevkinite-(Се) and Perrierite-(Се) from the Island Arc Quartz Gabbronorite–Dolerite of the Ayu-Dag Intrusion,Crimean Mountains

Geology of Ore Deposits - Chevkinite-(Се) and perrierite-(Се), which are characteristic minerals of alkaline igneous rocks and high-temperature alkaline alterations, are...     

Identification of potential areas for the occurrence of strong earthquakes in Himalayan arc region

Morphostructural zoning (MSZ) scheme of the Himalayan arc region as obtained from a joint study of topographic, geological and tectonic maps as well as satellite imagery is analysed. Three types of morphostructures have been determined: territorial units (blocks of different ranks), linear zones limiting these blocks (lineaments) and intersections of the lineaments (knots). Comparison of MSZ scheme with the know seismicity indicates epicenters of strong earthquakes (M≥6·5) clustered around some of these knots. Pattern recognition method is used to determine seismically potential areas for the occurrence of recognition method is used to determine seismically potential, for the occurrence of strong earthquakes of magnitude ≥M ₀. We have carried out two such studies for the Himalayan arc region, one forM ₀=6·5 and the other forM ₀=7·0. Out of a total number of 97 knots, 48 knots are found to be seismically potential for the occurrence of earthquake ofM≥6·5. The results of the study forM ₀=6·5 were presented in the symposium on “Earthquake Prediction” held in Strasbourg, France, March 1991 (Gorshkovet al 1991). The epicenter of Uttarkashi earthquake of magnitude,M _b=6·6 that occurred in the late hours of 19th October 1991 (UTC) lies in the vicinity of one such knot. The second study carried out subsequently shows that only 36, knots are potential for the occurrence of earthquakes ofM≥7·0, which include the knot, associated with theUttarkashi earthquake.     

Assessing Organic Carbon and Suspended Matter Runoff in the Yenisei Basin

The concentrations of organic matter that enters the aquatic environment in dissolved form, organic matter fractions adsorbed on suspended mineral particles, and the total concentration of suspended matter in the Yenisei water were studied using rapid optical methods. Spectral characteristics of light attenuation and absorption by river water and its filtrates were analyzed in summer. Total discharges of organic carbon and suspended matter by the river were evaluated.     

Fluid evolution and exhumation path of the Trivandrum Granulite Block,southern India

Contributions to Mineralogy and Petrology - In charnockites and host garnet-biotite gneisses of the Trivandrum Granulite Block (TGB), southern India, fluid inclusions are mainly represented by...