Composition transformation of terrigenous organic matter resinous-asphaltene components in super-deep wells in Siberia during meso- and apocatagenesis

K.V. Dolzhenko1*, L.S. Borisova1,2, A.N. Fomin1,2, Popova I.D.1,2

The evolution of the elemental composition of dispersed organic matter (DOM) heterocyclic components during catagenesis was traced via studying samples from the Tyumen-6 and Srednevylyuy-27 super-deep wells of Siberia. During mesocatagenesis, the composition of terrigenous DOM asphaltenes and resins undergoes directed changes: a decrease in hydrogen and oxygen content, enrichment with carbon, and graphitization of the structure. During apocatagenesis, due to high-temperature destruction, on the one hand, there is a condensation of individual blocks of asphaltenes and their transition to an insoluble form (formation of epiasphaltenic kerogens - EPAK). On the other hand, the lighter part of the asphaltenes goes into the formation of hydrocarbons (HC) and gas formation - a relative increase in the concentration of the former in % by mass of residual bitumoids is noted, as well as structural redistributions within benzene and spirit-benzene resins. In all studied parameters of the elemental composition, a symmetrical (unidirectional) transformation of resinous and asphaltene components of bitumoids from the Tyumen-6 and Srednevylyuy-27 super-deep wells under harsh thermobaric conditions is noted. The obtained results should be taken into account when predicting new oil and gas accumulation zones in deep-laid horizons.

Keywords: asphaltenes, resins, elemental composition, catagenesis, terrigenous organic matter, super-deep wells.

Catagenetic Trends in Composition and Structure Parameters of Asphaltenes

L.S. Borisova*, I.D. Timoshina

Abstract. Сatagenetic transformations of asphaltenes of organic matter (OM) from recent sediments and fossil rocks were studied on rocks sampled from different sedimentary basins (Timan-Pechora, Mezen, West Siberian, Kuznetsk, Aldan-Maya and Middle Amur) of Russia. Changes in the elemental composition of asphaltenes were analyzed with the Veselovsky’s model of the formation of major groups of fossil fuels using cO parameter (cO=(O/8-N)/(C/3)) as compared with the total carbon based on elemental analysis. Just as the Van Crevelin diagram, the plot built in C – cO coordinates for OM of various genetic forms demonstrates a significant difference in the asphaltenes composition evolution during catagenesis. At the same time, the cO parameter has notably increased in asphaltenes of both types of OM. Structural transformations of asphaltenes during catagenesis were identified in the course of high-resolution NMR (nuclear magnetic resonance) spectroscopy. The research results comprise data on carbon distributions in the aromatic and aliphatic groups in the investigated asphaltenes of different type OM of sediments and rocks at different stages of lithogenesis. A correlation between the asphaltene composition (cO) and structural parameters (Сal, Сar, С(CH2+CH)βγ, Сar(cond)) depending on thermocatalytic transformations is revealed; 3 successive areas of thermal maturation of asphaltenes were identified. The asphaltenes of terrestrial organic matter are distinguished by higher cO values and different carbon yields of aromatics (higher) and aliphatics (lower) throughout the catagenesis phase. The highly transformed aquatic OM is marked by surge condensation of aromatic rings in asphaltenes, which makes them at gradations MC31-2 similar to asphaltenes of the terrestrial type OM.

Keywords: organic matter, asphaltenes, elemental composition, NMR-spectroscopy, structure, catagenesis, evolution.

Accessory mineralisations in lherzolites of Northern Kraka massif (South Urals)

D.E.Savelieva, R.A.Gataullina

The findings of platinum group metal mineralization (PGM) and the distribution of platinum group elements (PGE) in lherzolites of the Northern Kraka massif are described. The total contents of PGE are approximately two orders of magnitude lower than those in chondrite and are close to pyrolite, relative to which the studied lherzolites are enriched in Pd and depleted in Ru. In segregations of PGMs, the presence of all PGEs (except rhodium) in various proportions was established. All found grains are divided into three contrasting types: the refractory triad Os-Ir-Ru, essentially platinum with the participation of Pd, and Cu-Pd. Almost all found PGM grains are localized either in the peripheral parts of grains of altered sulfides (heazlewoodite, pentlandite) or in the silicate matrix in the immediate vicinity of sulfide segregations. Based on the mineral associations and PGE distribution, a probable genesis of segregations has been suggested. Associations of Cu-Pd and Pd-Pt(+Cu) composition most likely formed during the crystallization of sulfides from the extracted partial melts. This is indicated by their close association with clinopyroxenes and the presence of relatively fusible platinoids and copper. The associations of Pt-Ir and Os-Ir-Ru(+Pt) composition are most likely restitic, formed in place of primary mantle sulfides as a result of extraction of more fusible elements and further desulphurization. The isolation of platinoids as their own mineral phases is associated with the influence of superimposed low-temperature processes - subsolidus redistribution during cooling and subsequent serpentinization.

Keywords: ultramafic rocks, ophiolite, lherzolite, PGM, PGE.

About micro- and nanoscale gold in the veil of gold-bearing territories (on the example of a mineralization site in the basin of the river Adamikha, Amur region)

I.V. Kuznetsova1, A.I. Dementienko2

Abstract. The article identifies the problem of the need to take into account micrometer (-1 mm+0.12 microns) and nanoscale (<0.12 microns) gold placers and weathering crusts to increase the objectivity of estimates of the prospects of their and eroded ore objects. The results of technological studies of gold-bearing deluvial deposits in the valley of the Adamikha river basin (Amur region) are presented. A quantitative assessment of the content of micro- and nanogold by fractions of loose material was made. It was found that in the studied sample of such material (weighing 50 kg), mostly (78%) refers to native gold with a dimension of <0.12 microns. Including 0.1% is in concentrator minerals, and 3.5% of the fraction (-3 microns) and probably colloidal in technical solutions of wet sieve.

Moreover, 3/4 of the total amount (18% visible and 57% invisible) of gold is concentrated in the fraction (-1+ 0.5 mm). It is established that, taking into account the free invisible gold, the resources of the precious metal of the object under study increase by 3.4 times. The possibility of a more objective quantitative assessment of the Au potential of promising areas, taking into account the content of fine gold, is shown. Possible ways of solving the problem of a more reliable assessment of geological reserves and estimation of forecast gold resources, taking into account the knowledge of the quantities of micro- and nanoscale fractions, are proposed. The authors believe that studies of the forms of allocation and distribution, including invisible (<0.12 microns) gold placers and weathering crusts will contribute to a more correct assessment of the studied gold-bearing objects and territories with the possibility of increasing the real resource potential of the precious metal in the region.

Keywords: Visible, micro- and nanogold, placers, weathering bark, gold ore deposits, potential of gold-bearing regions and territories.

Pseudorutile-leucoxene-quartz ores of Timan ‒ a new genetic type of titanium raw materials, prospects for industrial development

Makeyev A.B.1, Skublov S.G.2, 3, Galankina O.L.2, Vasiliev E.A.3, Krasotkina A.O.2

Abstract. The two largest deposits of Russia – Yaregskoye and Pizhemskoye belong to the same genetic type – hydrothermal-metamorphic indigenous deposits. They are located in the same Timan structure at a distance of no more than 230 km from each other. According to the total approved reserves and forecast resources of titanium dioxide, they are approaching 60% of the all-Russian and will form the basis of industrial titanium raw materials used in Russia in the near future. In the interests of technological mineralogy, morphological features, internal structure, chemical composition of grains of the two main titanium mineral phases leucoxene and pseudorutile, TiO2 polymorphs, as well as the composition of mineral microinclusions in these phases have been studied in detail. The compositions of all mineral phases in polished preparations of leucoxene and pseudorutile were analyzed by SEM-EDS method at the IPGG RAS, 147 chemical analyses were obtained at the point and many images of polished grains of anatase, leucoxene and pseudorutile were scanned over the area. In the leucoxene grains themselves, 12 mineral phases were diagnosed and characterized in the form of inclusions: pseudorutile, rutile, anatase, quartz, hydromuscovite-illite, kaolinite, siderite, zircon, xenotime, pyrite, florencite, monazite-kularite. TiO2 polymorphs are verified by Raman spectroscopy and X-ray diffraction analysis. New evidence has been obtained that the transformation of ilmenite into leucoxene occurs hydrothermally through intermediate phases ‒ Fe-rutile and pseudorutile; the enlargement of rutile crystals in the leucoxene grain itself is shown; the presence of secondary crystals of siderite, florencite and others inside the studied grains.

Key words: Pizhemskoye deposit, Yaregskoye deposit, hydrothermal metamorphogenic genesis, leucoxene, pseudorutile, rutile, anatase

The permanent temperature monitoring for flow rate quantification in production and injection wells

Kremenetskiy M. I.1*, Krichevskiy V. M.2, Solov'eva V. 12.,

A technique for monitoring of a production well rate dynamics based on the results of long-term temperature measurements in the wellbore at a certain depth which is significantly higher than the productive formation in real time is presented. The proposed analytical approaches for the well rate evaluation are based on the classical temperature behavior in the intervals of liquid and gas movement along the wellbore at a relatively far from the target formations. The temperature gradient in such intervals practically does not change with time and is close to geothermal, regardless of whether the inflow or injection is stable over time, or the well is in an unstable and cyclic production. It makes possible to find a relationship between the temperature change and heat flux density on the wellbore with simple and clear analytical approach, and to associate the heat flux density dynamics with the flow rate of the fluid moving along the wellbore. In the case of a multicomponent fluid mixture moving along the wellbore, temperature change in time depends on the complex parameter, which is the sum of terms, the number of which is equal to the number of fluids moving along the wellbore. Each term is the product of the flow rate and the heat capacity of the respective fluid. With a significantly non-stationary well production, a deconvolution operation can be used to determine the flow rate as a function of time by temperature changes. The presented approach is validated by mathematical modeling of a transient temperature processes in the wellbore, reservoir and bearing formations with unstable and cyclic inflow and by the results of long-term temperature monitoring in the wellbore of production and injection wells.

Keywords: reservoir surveillance of oil and gas fields, production and injection wells, production logging, temperature logging, stationary monitoring of temperature