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Lower Paleozoic oil and gas shale in the Baltic-Podlasie-Lublin Basin (central and eastern Europe) - a review

Poprawa Paweł

Geological Quarterly

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2020

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Vol. 64, No. 3

515--566

EN

In the Baltic-Podlasie-Lublin Basin, four potential lower Paleozoic shale reservoirs are identified: the Piaśnica, Sasino and Jantar formations, as well as the Mingajny shale. These units were diachronously deposited during the starved stages of Caledonian foredeep basin development, in the course of rising or high eustatic sea level. Across most of the basin, the shale formations analysed are saturated with light oil and condensate, and they are buried to depths of 2300-3500 m. The shale reservoirs reach the wet gas window at burial depths of 2800-4000 m, while dry gas accumulations occur at depths exceeding 3500-5000 m, except in the Biłgoraj-Narol Zone. The shale analysed might be generally classified as a moderate to low quality, and locally high quality, unconventional reservoir. Within the shale net pay zones, the average TOC content is 2-5 wt.% TOC. The exceptions are the Piaśnica Formation, for which this is 5-12 wt.%, and the Mingajny shale, which is TOC-lean (1.4-1.7 wt.%). The thickness of the shale net pay intervals in the most favourable locations, mainly on the Łeba Elevation, generally reaches 20 m, and locally exceeds 35 m. The shale reservoirs are saturated with hydrocarbons of good quality. Their permeability is low to moderate, often in the range of 150-200 mD, while total porosity average per borehole is commonly exceeds 6 %, reaching up to 10% at maximum, which might be considered as moderate to good. The clay minerals content is moderate to high (30-50%), and geomechanical characteristics of the shale formations are intermediate between brittle and ductile. No overpressure occurs in the basin, except for a dry gas zone in the SW Baltic Basin. In the Biłgoraj-Narol Zone, and to a lesser degree also in the Lublin region, pronounced tectonic deformation significantly limits shale gas/oil potential. Among 66 exploration boreholes drilled in the basin so far, only 5 were lateral boreholes with representative production test results. Hydrocarbon flow from the best boreholes was low to moderate, equal to 11.2 to 15.6 thousand m3/day for gas, and 157 bbl/day (~21.4 ton/day) for oil. There is, however, high potential to improve production flow rates, connected with the fracturing of two net pay intervals at one time, as well as with significant technological progress in the exploitation of shale basins during the last 5 years. Commercially viable production might be achieved for a single borehole with estimated ultimate recovery exceeding 30-50 thousand tons of oil, or 60-90 million m3 of gas.

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The Anisian carbonate ramp system of Central Europe (Peri-Tethys Basin): sequences and reservoir characteristics

Gotz A., Lenhardt N.

Acta Geologica Polonica

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2011

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Vol. 61, no. 1

59-70

EN

During Middle Triassic times, the Peri-Tethys Basin bordered the north-western Tethys shelf and was connected to the open Tethys Ocean via three seaways. Today, Lower Muschelkalk carbonates of this epeiric sea cover large parts of Central Europe, documenting the evolution of a low-relief, homoclinal, mud-dominated ramp system during the Anisian. In view of their geotectonic/climatic setting, depositional processes, facies architecture, and distribution, the rocks are considered as an outcrop analogue for layer-cake reservoirs of world-wide importance, e.g. the Permo-Triassic Khuff or Jurassic Arab carbonates in the Middle East. In general, two different reservoir types and their interplay might be considered: The proximal stacks of muddy dolostones (NW part of the basin) and the more distally developed grainy limestones (central and SE part of the basin). The rather uncommon depositional setting with minor relief and minimal accommodation contributed to both, the stratal and lateral facies development, and to unusual and possibly even "inverted" facies patterns with thick, grainy facies found in the more distal environments. Based on litho- and microfacies analyses, six main facies types are distinguished, building characteristic cyclic facies successions of different hierarchies. The stratal architecture of small-scale depositional sequ ences systematically changes in relation to their relative proximal-distal position on the Muschelkalk ramp system. Here, we present porosity and permeability data of the different facies types and within the basin-wide sequence stratigraphic framework. Dolo-wacke-/packstones and peloid grainstones attain the highest porosities of up to 24%, whereas bioclastic grainstones show porosities of up to 8%. The platy and nodular mud-/wackestone and most of the bioclastic wacke-/packstones typically show porosities below 2%. Even in the most porous strata, permeabilities do not exceed 10 mD, and only a few carbonates show higher permeabilities up to 90 mD. Within large-scale, third-order depositional sequences late highstand deposits represent the most permeable sediments.

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Opróbowanie otworów geotermalnych na podstawie wybranych doświadczeń w Polsce

Dubiel S., Sapińska-Śliwa A.

Technika Poszukiwań Geologicznych

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2009

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R. 48, nr 1

41--62

PL

W artykule opisano zagadnienie opróbowania otworów geotermalnych. W Polsce na potrzeby poszukiwania ropy naftowej i gazu ziemnego wykonano dużą ilość otworów. Zrealizowano także otwory specjalne na potrzeby ujęcia wód termalnych. W artykule przedstawiono wybrane polskie doświadczenia dotyczące opróbowań poziomów zbiornikowych wód termalnych. Przedstawiono wyniki zrealizowanych w Polsce opróbowań w otworach Koło IG-3, Koło IG-4, Poddębice IG-1 oraz Mszczonów IG-1. W artykule zamieszczono także zastosowanie rurowego próbnika złoża typu Inflatable dla odwiertów naftowych.

EN

The geothermal well testing procedure is described in this papier. Numerous well have been drilled in Poland for crude oil and natural gas prospecting purposes. Special wells were also drilled for purposes related to geothermal energy. The Polish experience in testing geothermal water reservoirs is described. The results of tests carried out in Poland at the Koło IG-3, Koło IG-4 and Poddębice IG-1 and Mszczonów IG-1 wells are presented. Examples of the application of inflatable DST tools to probe for aquifers within oil wells are described.