Autor: Sechman, H. - Prolib Integro

Skocz do pozycji: 1.

Tytuł:: Głębokość poboru próbki gazu podglebowego w powierzchniowych badaniach geochemicznych - próba optymalizacji
Sampling of soil gas in surface geochemical surveys -- an attempt of depth optimization
Autorzy:: Sechman, H.
Tematy:: powierzchniowe badania geochemiczne
głębokość opróbowania
gaz podglebowy
lekkie alkany
strefa aktywnej wymiany
surface geochemical survey
sampling depth
soil gases
light alkanes
active exchange zone; Pokaż więcej
Wydawca:: Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Powiązania:: https://bibliotekanauki.pl/articles/183486.pdf Link otwiera się w nowym oknie
Opis:: W pracy przedstawiono wyniki badań nad optymalizacją głębokości poboru próbek gazu podglebowego przy powierzchniowych badaniach geochemicznych. Badania wykonano w dwóch obszarach: w niecce wałbrzyskiej i w rejonie Karlina na Pomorzu Zachodnim. Badania wykonane w niecce wałbrzyskiej nad zlikwidowanymi kopalniami węgla kamiennego wykazały, że najbardziej dogodny dla opróbowań geochemicznych jest interwał głębokościowy 1.0-1.8 m, który położony poniżej strefy aktywnej wymiany sięgającej do głębokości ok. 1 m charakteryzuje się wyrazistym sygnałem geochemicznym pochodzenia wgłębnego. Badania w rejonie Karlina na Pomorzu Zachodnim, wykonane nad akumulacjami naftowymi, polegały na ocenie uzyskanych wielkości stężeń węglowodorów gazowych szeregu metanowego na głębokościach 1.2 m i 1.8 m. Wykazały one, że głębokość 1.2 m jest optymalna dla powierzchniowych opróbowań geochemicznych, realizowanych metodą gazu wolnego w tym obszarze. Analogiczną głębokość opróbowania gazowego można przyjąć dla obszaru niecki wałbrzyskiej. W celu potwierdzenia uzyskanych wyników podobne badania powinny zostać przeprowadzone w innych perspektywicznych złożowo obszarach Polski.
The paper presents the results of optimization of sampling depth for soil gas applied in the surface geochemical survey. The studies were carried out in two areas: the Wałbrzych Trough and the Karlino area (Western Pomerania). The studies in the Wałbrzych Trough was carried out over the closed and remediated coal mines. The results demonstrated that sampling depth interval 1.0-1.8 meters is an optimum for surface geochemical survey as it is located beneath the active exchange zone (i.e. beneath 1.0 meter) but provides distinct geochemical response from deep sources. The studies in the Karlino area (Western Pomerania) was carried out over oil and gas pools. It was found that 1.2 meter depth is an optimum for geochemical sampling with the "free" gas method in this area. The some sampling depth can be apply on in the Wałbrzych Trough. Such studies must be passed in other areas of Poland to confirm this depth of sampling.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 2.

Tytuł:: Pomiary emisji metanu w wybranych rejonach polskich Karpat Zewnętrznych
Methane emission measurements in selected areas of the Polish Outer Carpathians
Autorzy:: Sechman, H.
Dzieniewicz, M.
Tematy:: powierzchniowe badania geochemiczne
Karpaty
gaz glebowy
metoda komór statycznych
emisja metanu
surface geochemical survey
Carpathians
soil gas
static chambers method
emission of methane; Pokaż więcej
Wydawca:: Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Powiązania:: https://bibliotekanauki.pl/articles/183731.pdf Link otwiera się w nowym oknie
Opis:: W pracy przedstawiono wyniki pomiarów dynamiki stężeń metanu oraz jego emisji. Badania wykonano metodą komór statycznych na wybranych 16 stanowiskach położonych na obszarze polskich Karpat Zewnętrznych. Mierzono zmiany stężeń gazów węglowodorowych oraz dwutlenku węgla naturalnie uchodzących do atmosfery z powierzchni terenu, a także z głębokości 1 metra. Zmiany stężeń analizowano w różnych interwałach czasowych: od kilku minut do prawie 30 godzin. Stężenia metanu wahały się od ok. 1.6 ppm do prawie 8000 ppm. Dynamika zmian tych stężeń była najwyraźniejsza, kiedy metan wypływał z otworu o głębokości 1 m i zmieniała się w przedziale od -0.23 do 100.7 ppm x min-1. Obliczone wielkości emisji wahały się od -24.5 do 10 606.9 mg x m-2 x d-1, przy średniej 304.5 mg x m-2 x d-1 i medianie 0.21 mg x m-2 x d-1. Wyniki badań pozwoliły na zoptymalizowanie metodyki pomiarów terenowych, a także na szacunkową ocenę ilości metanu uwalnianego z jednostki powierzchni orogenu karpackiego w jednostce czasu.
The paper presents measurement results of dynamics of methane concentrations and its emission. The investigations were carried out with application of the method of static chambers in 16 stations located in the Polish Outer Carpathians. The measurements included changes of concentrations of hydrocarbon gases and carbon dioxide, which naturally escape to the atmosphere from the land surface and flow from the depth of 1 m. The concentration changes were analyzed in various time intervals: from a few minutes up to almost 30 hours. Methane concentrations ranged from approximately 1.6 ppm up to nearly 8000 ppm. Dynamics of its concentrations was most distinct when it was flowing from the depth of 1 m and it was changing within the range of -0.23 to 100.7 ppm x min-1. The calculated emission quantities ranged from -24.5 to 10 606.9 mg x m-2 x d-1, with the mean value equal to 304.5 mg x m-2 x d-1 and median of 0.21 mg x m-2 x d-1. The results of the investigations enabled the authors to optimize the methodology of field measurements and to estimate the quantity of methane which escapes from an area unit of the Carpathian orogen during a time unit.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 3.

Tytuł:: Analiza wyników powierzchniowych badań geochemicznych w transgranicznej strefie Karpat polskich i ukraińskich
Analysis of results of surface geochemical surveys in the transfrontier zone of the Polish and Ukrainian Carpathians
Autorzy:: Sechman, H.
Dzieniewicz, M.
Tematy:: Karpaty fliszowe
Polska
Ukraina
prospekcja naftowa
powierzchniowe badania geochemiczne
gaz glebowy
alkany
Polska
Ukraine
flysch Carpathians
oil and gas fields
surface geochemical survey
soil gas
alkanes; Pokaż więcej
Wydawca:: Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Powiązania:: https://bibliotekanauki.pl/articles/183733.pdf Link otwiera się w nowym oknie
Opis:: W pracy przedstawiono wyniki rozpoznawczych powierzchniowych badań geochemicznych wykonanych w latach 2007-2008 we wschodniej części polskich i zachodniej części ukraińskich Karpat Zewnętrznych, na północ od nasunięcia dukielskiego. Celem badań była ocena możliwości występowania wgłębnych akumulacji węglowodorów w obszarze cechującym się powszechnym występowaniem wycieków ropnych na wychodniach intensywnie sfałdowanych i głęboko rozciętych przez erozję warstw. Badania wykonano wzdłuż 11 profili przebiegających poprzecznie do rozciągłości fliszowych jednostek strukturalno-facjalnych. Ogółem pobrano 890 próbek gazu glebowego, w których określono stężenia węglowodorów gazowych i helu. Stężenia metanu, sumy wyższych alkanów, gazowych alkenów i helu dochodziły odpowiednio do 50% obj., 0.4% obj., 132 ppm i 52 ppm. Anomalne stężenia alkanów, przedstawione graficznie na tle głównych jednostek tektonicznych Karpat oraz udokumentowanych akumulacji złożowych, generalnie potwierdziły obecność tych ostatnich. Inne anomalie wskazują na możliwość występowania nieudokumentowanych dotąd, wgłębnych akumulacji węglowodorów.
The paper presents results of reconnaissance surface geochemical surveys carried out in the years 2007 and 2008 in the eastern Polish Carpathians and western Ukrainian Carpathians between the Carpathian Foredeep and Dukla Overthrust. The surveys intended to assess the possibility of occurrence of subsurface hydrocarbon accumulations in the area characterized by common occurrence of oil seeps at outcrops of beds, which had been intensely folded and deeply dissected by erosion. The surveys were conducted along 11 profiles. The profiles were running transversally to the strike of flysch structural-facies units. The geochemical surveys consisted in taking 890 soil-gas samples, in which concentrations of gaseous hydrocarbons and helium were determined. Concentrations of methane, higher alkanes, gaseous alkenes and helium reached to nearly 50 vol.%, 0.4 vol.%, 132 ppm and 52 ppm, respectively. The anomalous alkanes concentrations, graphically presented against the background of major Carpathian tectonic units and documented hydrocarbon deposits, have confirmed, in general, the existence of the deposits, whereas some of the concentrations have indicated possible occurrence of other, still undocumented subsurface hydrocarbon accumulations.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 4.

Tytuł:: Powierzchniowe badania geochemiczne w wybranych obszarach polskich i ukraińskich Karpat fliszowych
Surface geochemical survey in selected areas of the Polish and Ukrainian Flysch Carpathians
Autorzy:: Dzieniewicz, M.
Sechman, H.
Tematy:: Karpaty fliszowe
Polska
Ukraina
złoża ropy naftowej i gazu ziemnego
powierzchniowe badania geochemiczne
gaz glebowy
alkany
Polska
flysch Carpathians
Ukraine
oil and gas fields
surface geochemical survey
soil gas
alkanes; Pokaż więcej
Wydawca:: Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Powiązania:: https://bibliotekanauki.pl/articles/183914.pdf Link otwiera się w nowym oknie
Opis:: W pracy przedstawiono wyniki rozpoznawczych powierzchniowych badań geochemicznych wykonanych w wybranych strefach polskich i ukraińskich Karpat fliszowych. Ich celem była ocena możliwości występowania wgłębnych akumulacji węglowodorów. Badania wykonano wzdłuż ośmiu profili o łącznej długości ok. 150 km, przebiegających generalnie z NE na SW. Polegały one na poborze próbek gazu glebowego, w których określano stężenia węglowodorów gazowych i helu. Ogółem pobrano 315 próbek z punktów rozmieszczonych w odstępach ok. 500-metrowych. Stężenia metanu wahały się od 0.9 ppm do prawie 50% obj., stężenia wyższych alkanów dochodziły do ok. 0.4% obj., a stężenia gazowych alkenów do ok. 132 ppm. Stwierdzono również obecność helu o stężeniu dochodzącym do 52 ppm. Zmiany stężeń składników węglowodorowych przedstawione graficznie na tle istniejącego modelu geologiczno-złożowego potwierdzają dotychczasowe rozpoznanie złożowe, a także wskazują na możliwość występowania innych, nieudokumentowanych dotąd, akumulacji wgłębnych.
The paper presents results of reconnaissance surface geochemical survey carried out in selected zones of the Polish and Ukrainian Flysch Carpathians. It intended to assess the possibility of occurrence of subsurface hydrocarbon accumulations. The survey was conducted along 8 profiles with total length of approximately 150 km, in general running from NE to SW, and consisted in taking samples of soil gas, in which concentrations of hydrocarbons and helium were determined. In sum, 315 samples were taken at points with the 500 m spacing. Concentrations of methane ranged from 0.9 ppm to almost 50 vol. %, concentrations of higher alkanes amounted to approximately 0.4 vol. % and concentrations of gaseous alkenes came up to approximately 132 ppm. Also presence of helium was recorded, its concentration amounting to 52 ppm. Variations in concentration of hydrocarbon constituents, graphically presented against the background of the existing geological and reservoir model, confirm the previous recognition of oil and gas fields and are indicative of opportunity of occurrence other, still undocumented subsurface accumulations.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 5.

Tytuł:: Badanie składu gazów glebowych - przykłady zastosowań w prospekcji naftowej i ochronie środowiska
Investigation of soil gas composition - examples of application in petroleum exploration and environment protection
Autorzy:: Dzieniewicz, M.
Sechman, H.
Górecki, W.
Tematy:: powierzchniowe badania geochemiczne
skład gazu glebowego
lekkie węglowodory
złoża ropy naftowej i gazu ziemnego
ochrona środowiska
surface geochemical survey
soil gas composition
light hydrocarbons
oil and gas fiels
environmental protection; Pokaż więcej
Wydawca:: Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Powiązania:: https://bibliotekanauki.pl/articles/183369.pdf Link otwiera się w nowym oknie
Opis:: The paper presents examples that confirm possibility of using the soil gas method. Soil gas method might be applied to petroleum exploration, to checking of well tightness and underground gas storage, to checking of underground gas pipelines and to prediction of gas hazard in the near-surface zone caused by coal mine closure in the Wałbrzych Coal District.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 6.

Tytuł:: Measurement of methane flux in the selected area of the Polish Outer Carpathians – preliminary research
Autorzy:: Twaróg, A.
Guzy, P.
Sechman, H.
Tematy:: emission
atmosphere
soil; Pokaż więcej
Wydawca:: Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Powiązania:: https://bibliotekanauki.pl/articles/184497.pdf Link otwiera się w nowym oknie
Opis:: Methane emissions associated with the hydrocarbon-generation process occurring in sedimentary basins are considered to be one of two types of geologic sources of methane emissions to the atmosphere. Current methane emissions releasing from geological sources amount 45–60 Tg CH 4 yr –1. The measured values of flux migrating from soil into the atmosphere are influenced by a series of factors, e.g. porosity and permeability of overlying layers, occurrence of cracks and faults, atmospheric pressure, seasonal temperature fluctuations and presence of methanotrophic bacteria. The latter, as a result of methane consumption, may trigger negative flux values (Etiope 2015). Previously, the methane emission measurements in the Polish Outer Carpathians were carried out with a method of static chambers (Sechman & Dzieniewicz 2009). The studies presented in the paper consisted in initial methane emission measurements by flux meter. Their purpose was to examine distribution of methane fluxes on the land surface, as well as change in emission along with depth, omitting the ‘screening’ near-surface zone. The studies were carried out in a small area of the Carpathian petroleum oil region, nearby Rymanów, between October and December 2015. Measurement of the methane fluxes were performed with application of a portable flux meter (West System 2012). The device performs one measurement per second on average, recording concentration changes in time (ppm/s). Average measurement time was 360 seconds. When a high methane concentration was registered, gas samples were collected from the accumulation chamber and directed to a detailed chromatographic analysis (field sampling and analytical procedure – see Sechman & Dzieniewicz 2009). There were 137 measurements taken on 87 stands in total, recording emission from the land surface, and emission with application of 1-m deep holes – in order to omit the “screening” near-surface zone (Sechman & Dzieniewicz 2009). The emission was recorded along the 1000- m long profile, where samples of soil gas were collected previously, and around the drill holes covered with soil. Furthermore, during the process of drilling 4 boreholes, there were CH 4 test emission measurements taken examining change in methane flux with depth (to 10 m). In case of the KB-7 borehole, measurements were taken 1 and 22 days after the drilling. The natural emission was recorded on 70 measuring stations. The flux was identified only in 30% of the performed measurements. Negative emission was predominant within the examined area (68% of all measurements), with an average value of −3.8 mg∙m −2 ∙d −1. Average value of the positive flux reached 3 mg∙m −2 ∙d −1. Range of the measured flux values is comprised within the scope from −5.2 mg∙m −2 ∙d −1 to 14.9 mg∙m −2 ∙d −1. Emission measurements with the additional holes were carried out at 37 positions. Fluxes with positive values were identified in 6 of them, while the negative values were recorded in 4. Range of the measured flux values with the additional hole was from −6.4 mg∙m −2 ∙d −1 to 2 mg∙m −2 ∙d −1 ; average negative and positive flux values are as follows, respectively: −2.3 mg∙m −2 ∙d −1 and 1.3 mg∙m −2 ∙d −1. Within the examined area, methane emission from the land surface, and to the depth of 1 m, was identified only in 30% of measurements. The measurements are characterized by low values, from −6.4 mg∙m −2 ∙d −1 to 14.9 mg∙m −2 ∙d −1. Results of test emission measurements recorded in subsequently drilled depth intervals, performed for 4 drilling boreholes. For the KB-6, KB-7, KB-8 and KB-10 boreholes, average values of methane emission from subsequent depth intervals were as follows, respectively: 49.2, 68.6, 3.5 and 1.5 mg∙m −2 ∙d −1. These results are higher than values of natural emission measured on the land surface or with application of holes to 1 m. The highest emission values were recorded for the KB-7 borehole. A detailed distribution of CH 4 flux values was correlated with a lithology and molecular composition of gas collected from the accumulation chamber in three depth intervals (3.5 m, 5.5 m and 10 m). Results of the gas molecular analysis prove that the source of methane emission is characterized by both microbial and endogenous origin. It is assumed that occurrence of components heavier than methane in the samples, arises from their depth origin (Saunders et al. 1991). An increase of methane concentration in intervals related to occurrence of shales – may suggest its recent origin. It also needs to be noticed that C 1 /C 2 ratio values (from 207 to 807) increase along with depth, what may prove prevailing share of microbial methane. When 24 hours passed after drilling the KB-7 borehole, the emission value dropped to 0.6 mg∙m −2 ∙d −1, and after about three weeks, during an hourly emission measurement, a positive flux of 0.1 mg∙m −2 ∙d −1 was observed in time 0–470 second and a negative flux of −0.05 mg∙m −2 ∙d −1 was observed in time 480–2660 second. Furthermore, small concentrations of ethane (0.006 ppm) and ethylene (0.005 ppm) were identified in gas sample collected after 22 days. The emissions study conducted in the Rymanów area (Outer Carpathians) indicates the mixed source of methane. In order to determine the detailed methane source, it would be necessary to perform an analysis of the carbon isotopic composition in the samples taken. The low emission values measured on the land surface results from the fact that the emissions were suppressed by the sealing overburden layer. The measurements taken 1 day and then 22 days after drilling – in the KB-7 stabilized borehole, show a decline in emissions value. This may result from an insignificant inflow of hydrocarbons from the depth, bacterial oxidation of these hydrocarbons, and from the influx of air to the borehole.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 7.

Tytuł:: Surface geochemical survey at Starunia palaeontological site and vicinity (Carpathian region, Ukraine)
Autorzy:: Sechman, H.
Kotarba, M. J.
Dzieniewicz, M.
Tematy:: surface geochemical survey
stable carbon isotopes
methane origin
gaseous hydrocar bon C2-C5
carbon dioxide origin
woolly rhinoceros
Starunia
Carpathian region
Ukraine; Pokaż więcej
Wydawca:: Polskie Towarzystwo Geologiczne
Powiązania:: https://bibliotekanauki.pl/articles/191493.pdf Link otwiera się w nowym oknie
Opis:: A surface geochemical survey was carried out in an abandoned ozokerite mine in Starunia, where remnants of a mammoth and three woolly rhinoceroses and one almost completely preserved rhinoceros carcass were found in 1907 and 1929. In total, 689 measurement sites were defined within the selected 300×350 m rectangle (ca. 10.5 ha). The analysed soil gases vary in their molecular and isotopic compositions. Several zones with anomalous methane concentrations over 10 vol% were identified in the study area. These anomalous concentrations correlate well with total C2-C5 alkane anomalies (over 1 vol%). The zones with carbon dioxide concentrations over 15 vol% are generally shifted SW of those, where the methane and the sum of C2-C5 alkanes anomalies were identified. High helium concentrations of crustal origin (over 0.001 vol%) are clustered near fault zones. In a majority of cases methane is of thermogenic origin, migrating to the near-surface zone from deep-seated accumulations. Microbial methane, or methane with a high microbial component, is genetically related to recent swamps. The high variability of concentrations of gaseous components together with the highly variable isotopic composition of individual gases in the soil, indicate their thermogenic and/or microbial origin, and point to the lithological diversity of Quaternary sediments in the study area. Several zones with thermogenic gaseous hydrocarbons and helium were delineated. It is likely that during the Pleistocene winters, under a thick ice and snow cover, the tundra lake and swamp zones around outflows of brines, oil, helium and thermogenic gases had a higher temperature, which resulted in melting and cracking of the ice cover. These sites would be more prospective for future search of well-preserved large vertebrates.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 8.

Tytuł:: Distribution and origin of gaseous hydrocarbons and carbon dioxide in the Quaternary sediments at Starunia palaeontological site and vicinity (Carpathian region, Ukraine)
Autorzy:: Kotarba, M. J.
Sechman, H.
Dzieniewicz, M.
Tematy:: near-surface geochemical survey
depth gas distribution
stable carbon isotopes
gaseous hydrocarbon origin
carbon dioxide origin
Quaternary sediments
woolly rhinoceros
Starunia palaeontological site
Ukrainian Carpathians; Pokaż więcej
Wydawca:: Polskie Towarzystwo Geologiczne
Powiązania:: https://bibliotekanauki.pl/articles/191503.pdf Link otwiera się w nowym oknie
Opis:: Near-surface gases were investigated in Starunia, where remains of mammoth and woolly rhinoceroses were discovered at the beginning of the 20th century. Samples were collected at 30 measurement sites, from 0.8, 1.6, 2.4, 3.2 and 4.0 m depths and analysed for their molecular and isotopic compositions. Most of the methane and all higher gaseous hydrocarbons accumulated within the near-surface zone are of thermogenic origin. The distribution of thermogenic methane and higher gaseous hydrocarbons in Quaternary sediments is variable and, generally, increases with depth. Microbial methane or a mixture of microbial and thermogenic methane also occurs at the near-surface zone. The presence of hydrogen and alkenes in the near-surface gases also suggests a contribution from recent, microbial processes. Helium of crustal origin migrated through the Rinne Fault and other tectonic zones located in the study area, and was subsequently dispersed during migration through the lithologically diversified Pleistocene and Holocene sediments. The high variability of the carbon dioxide concentration and stable carbon isotope composition at various depths in the near-surface zone is caused by its polygenetic origin (thermogenic, microbial, and oxidation of hydrocarbons and Quaternary organic matter), and also by its dissolution in water and oil during migration through lithologically diversified Pleistocene and Holocene sediments. Zones of thermogenic methane occurrence within Pleistocene sediments, dominated by muds saturated with bitumen and brines, provide the most favourable environment for preservation of large extinct mammals. It is likely that during the Pleistocene winters, when thick ice and snow covered the tundra lake and swamp, zones of outflow of brines, oils, helium, and thermogenic gaseous hydrocarbons had a higher temperature, which could have resulted in melting and cracking of the ice cover and drowning of large mammals. The most favourable conditions for preservation of large, extinct mammals probably still exists in the vicinity of sampling probe sites Nos 21, 22, 23 and 36. Zones of dominance of microbial methane concentrations are less favourable sites for preservation of extinct mammals, because this methane was generated within recent swamps and also within recent descending meteoric waters which infiltrated into Pleistocene and Holocene sediments. Older Pleistocene microbial gases have already escaped to the atmosphere.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 9.

Tytuł:: Molecular and isotopic compositions of gases adsorbed to near surface sediments at Starunia palaeontological site and vicinity (Carpathian region, Ukraine)
Autorzy:: Dzieniewicz, M.
Sechman, H.
Kotarba, M. J.
Tematy:: near-surface geochemical survey
adsorbed gases
origin of gaseous hydrocarbons
origin of carbon dioxide
Quaternary sediments
Starunia palaeontological site
Carpathian region
Ukraine; Pokaż więcej
Wydawca:: Polskie Towarzystwo Geologiczne
Powiązania:: https://bibliotekanauki.pl/articles/191497.pdf Link otwiera się w nowym oknie
Opis:: The near-surface geochemical survey of gases desorbed from sediment samples was carried out in the area of an abandoned ozokerite mine in Starunia, where remnants of mammoth and three woolly rhinoceroses and one almost completely preserved rhinoceros carcass were discovered in 1907 and 1929. Numerous hydrocarbon seeps (gas and oil "eyes") occur on the surface of the study area. Analyses of molecular and stable carbon isotope compositions of adsorbed gases were carried out in two variants. The first included sampling of cuttings from 30 auger boreholes at depths of 4.8, 5.6 and 6.4 m. In total, 88 samples were collected. In the second variant core samples were collected from 17 selected boreholes. In total, 78 samples were taken from various depths to 12 m. The results of molecular composition analyses of desorbed gases indicated high saturation of near-surface sediments with the oil. The highest concentrations of alkanes were detected in Miocene strata. Hydrocarbon migration from deep accumulations to the surface was relatively fast and proceeded along the faults, fractures and cracks. In the near-surface zone hydrocarbons were subjected to oxidation and dehydrogenation, which resulted in generation of unsaturated hydrocarbons and hydrogen. These processes were most intensive in the Pleistocene sediments and in the mine dumps. Increased concentrations of hydrogen may also originate from water radiolysis in the presence of hydrocarbons. Concentrations of carbon dioxide in the adsorbed gases show the higher values in comparison with the analysed gaseous compounds. However, a slight increase in CO2 concentration was detected in the mine dump, which may indicate conditions more favourable for hydrocarbon oxidation. Carbon dioxide from the analysed adsorbed gases is of thermogenic origin. Occasionally, insignificant influence of secondary hydrocarbon oxidation and/or Quaternary organic matter can be observed. Concentrations of alkanes, alkenes and carbon dioxide in the gas derived from desorption of rock samples are lower and the concentration of hydrogen is higher than those measured in free gases. This indicates that additional effects from recent (e.g. microbial) processes are absent.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 10.

Tytuł:: Surface geochemical anomalies in the vicinity of the Wańkowa Oil Field (SE Polish Carpathians)
Autorzy:: Sechman, H.
Kuśmierek, J.
Machowski, G.
Guzy, P.
Dzieniewicz, M.
Tematy:: surface geochemical survey
soil gas
light hydrocarbons
oil traps
Skole Nappe
Outer Carpathians
Polska; Pokaż więcej
Wydawca:: Polskie Towarzystwo Geologiczne
Powiązania:: https://bibliotekanauki.pl/articles/191525.pdf Link otwiera się w nowym oknie
Opis:: The oil accumulations discovered in the Skole Synclinorium (eastern part of Polish Outer Carpathians) are located in zones of pinch-out of the Kliva Sandstone. An example is the Wańkowa Oil Field, which contains the largest oil reserves in the region. As the seismic identification of this type of hydrocarbon trap is ambiguous, a surface geochemical survey was carried out in the vicinity of the Wańkowa Oil Field along an experimental line perpendicular to the fold axes. A traverse across the zones with anomalous seismic records indicated the presence of undiscovered lithological traps. During the surface geochemical survey, 94 samples of soil gas were collected from a depth of 1.2 m and then investigated chromatographically. The spacing of sampling sites was 100 m, which was reduced to 50 m in the Wańkowa Oil Field area. The maximum concentrations of CH₄ and total alkanes C₂-C₅ detected in samples were: 4250.0 ppm (0.425 vol. %) and 0.43 ppm, respectively. The first of these was detected at measurement point no. 86, located over the Wańkowa Field and the second at point no. 59, about 1,300 m south of the Wańkowa Field. The chemical analyses also detected maximum values of total alkenes C₂-C₄, H₂ and CO₂: 0.147 ppm, 0.042 vol. % and 4.4 vol. %, respectively. The results of the surface geochemical survey were integrated with observations on subsurface geological structures, which were interpreted on the basis of seismic data. This procedure permitted the documentation of anomalous concentrations of alkanes in the near-surface zone and contributed to an understanding of the tectonics of the hydrocarbon reservoirs in depth. The pattern of geochemical anomalies here is controlled by anticlines made up of Early Oligocene–Paleocene sediments and by overthrusts that displace these structures. The hydrocarbons migrated from condensate and/or oil accumulations located at various depths. The character of the anomalous zone discovered over the Wańkowa Oil Field is related to the effective sealing of hydrocarbon traps and/or the relatively low pressure caused by the production of oil for 130 years. However, this anomaly also may be the result of hydrocarbon migration from deeper, as yet undiscovered gas or gas-condensate accumulations, hosted in older reservoirs forming the hinge of the Ropienka-Łodyna Mine Anticline. The most pronounced anomalies were detected over the Wańkowa Village - Bandrów and Grabownica-Załuż anticlines. The active hydrocarbon dispersion in this zone may have resulted from the presence of overthrusts displacing the structures. Moreover, these anomalies may indicate the presence of shallow, maybe poorly sealed hydrocarbon accumulations.
Dostawca treści:: Biblioteka Nauki

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