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

Abstract

In the Bal tic-Podlasie-Lublin Ba sin, four po ten tial lower Pa leo zoic shale res er voirs are iden ti fied: the Piaśnica, Sasino and Jantar for ma tions, as well as the Mingajny shale. These units were diachronously de pos ited dur ing the starved stages of Cal edo nian foredeep ba sin de vel op ment, in the course of ris ing or high eustatic sea level. Across most of the ba sin, the shale for ma tions ana lysed are sat u rated with light oil and con den sate, and they are bur ied to depths of 2300-3500 m. The shale res er voirs reach the wet gas win dow at burial depths of 2800-4000 m, while dry gas ac cu mu la tions oc cur at depths ex ceed ing 3500-5000 m, ex cept in the Biłgoraj-Narol Zone. The shale ana lysed might be gen er ally clas si fied as a mod erate to low qual ity, and lo cally high qual ity, un con ven tional res er voir. Within the shale net pay zones, the av er age TOC content is 2-5 wt.% TOC. The ex cep tions are the Piaśnica For ma tion, for which this is 5-12 wt.%, and the Mingajny shale, which is TOC-lean (1.4-1.7 wt.%). The thick ness of the shale net pay in ter vals in the most fa vour able lo ca tions, mainly on the Łeba Elevation, gen er ally reaches 20 m, and lo cally ex ceeds 35 m. The shale res er voirs are sat u rated with hy dro carbons of good qual ity. Their per me abil ity is low to mod er ate, of ten in the range of 150-200 mD, while to tal po ros ity av er age per bore hole is com monly ex ceeds 6 %, reach ing up to 10% at max i mum, which might be con sid ered as mod er ate to good. The clay min er als con tent is mod er ate to high (30-50%), and geomechanical char ac ter is tics of the shale for ma tions are inter me di ate be tween brit tle and duc tile. No overpressure oc curs in the ba sin, ex cept for a dry gas zone in the SW Bal tic Basin. In the Biłgoraj-Narol Zone, and to a lesser de gree also in the Lublin re gion, pro nounced tec tonic de for ma tion sig nif i cantly lim its shale gas/oil po ten tial. Among 66 ex plo ra tion bore holes drilled in the ba sin so far, only 5 were lat eral bore holes with rep re sen ta tive pro duc tion test re sults. Hy dro car bon flow from the best bore holes was low to mod er ate, equal to 11.2 to 15.6 thou sand m 3 /day for gas, and 157 bbl/day (~21.4 ton/day) for oil. There is, how ever, high po ten tial to im prove pro duc tion flow rates, con nected with the frac tur ing of two net pay in ter vals at one time, as well as with sig nif i cant tech no log i cal prog ress in the ex ploi ta tion of shale bas ins dur ing the last 5 years. Com mer cially vi a ble pro duc tion might be achieved for a sin gle bore hole with es ti mated ul ti mate re cov ery ex ceed ing 30-50 thou sand tons of oil, or 60-90 mil lion m 3 of gas.

Use of Cluster Analysis to Group Organic Shale Gas Rocks by Hydrocarbon Generation Zones

“…After many tests, it was found that the best results, due to the optimal number of clusters (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20), were obtained for a maximum distance d max of 3.2 (two standard deviations from the set of standardized distances) for the furthest neighbor method and a d max of 4.8 (on the order of three standard deviations for the set of standardized distances) in the case of Ward's method. In this analysis variant, particular attention was paid to the mean R o values (within each cluster), allowing the classification of samples from a given cluster into one of the windows (gas, condensate, or oil).…”

“…The main task is to assess the potential of unconventional hydrocarbon resources in selected geological structures in Poland. The assessment of the potential of hydrocarbon resources is based on total organic carbon (TOC) data, the thermal maturity of the organic matter and the genetic type of kerogen [17,18]. The carried-out studies show that shale type of geological structures are characterized by high sedimentological variability and high variability of the physicochemical properties of the organic matter [19][20][21][22].…”

First Evidence of the Post-Variscan Magmatic Pulse on the Western Edge of East European Craton: U-Pb Geochronology and Geochemistry of the Dolerite in the Lublin Podlasie Basin, Eastern Poland

“…The LPB had developed in Late Neoproterozoic as an active rift, but has been aborted and gradually turned into the Cambrian-Ordovician post-rift thermal sag on Baltica's passive margin. Its distinguishing feature is the almost continuous, vertical profile for the Upper Neoproterozoic to Silurian sediments [47,48]. In this part of the EEC the dominant evidence of igneous activity remains, the volcanogenic Sławatycze Formation, in E Poland, being analogous to the Volyn Series, in Ukraine [6,7].…”

Ordovician and Silurian Formations of the Baltic Syneclise (NE Poland): An Organic Geochemistry Approach

“…Along with Alum Shale, good and excellent source rocks such as Piśnica, Sasino, Jantar, and Mingajny formations are present throughout the Early Paleozoic strata and are widespread in the Baltic Basin region [9,10,23,24]. The increasing interest in the occurrence of unconventional hydrocarbon deposits has drawn attention to the remaining organic-rich shales, particularly in Late Ordovician and Early Silurian strata of the region [25][26][27][28][29].…”