Hy Dro Car Bon Gen Er a Tion/Ex Pul Sion Mod El Ling of the Lower Pa Leo Zoic Po Ten Tial Source Rocks in the Gryfice and Kołobrzeg Blocks (NW Poland)
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Geo log i cal Quar terly, 2010, 54 (2): 183–196 Hy dro car bon gen er a tion/ex pul sion mod el ling of the lower Paleozoic po ten tial source rocks in the Gryfice and Kołobrzeg blocks (NW Po land) Paweł KOSAKOWSKI, Magdalena WRÓBEL and Paweł POPRAWA Kosakowski P., Wróbel M. and Poprawa P. (2010) – Hy dro car bon gen er a tion/ex pul sion mod el ling of the lower Pa leo zoic po ten tial source rocks in the Gryfice and Kołobrzeg blocks (NW Po land). Geol. Quart., 54 (2): 183–196. Warszawa. The lower Paleo zoic source rocks in the offshore part of the Gryfice and Kołobrzeg blocks (NW Po land) were studied through geochem i- cal data and nu meri cal mod el ling. The geo chem i cal study re vealed a pres ence of ef fec tive source rocks in Caradocian strata, but with low hydro car bon po tential . The rem aining lower Pa leozoic source rock hori zons were not docu mented by core sam ples. The tim ing of hydro - car bon gener a tion and ex pulsion was mod elled for the K1-1/86 and L2-1/87 boreholes lo cated in the Gryfice and Kołobrzeg blocks, re- spectivel y. 1-D and 2-D mod elling indi cate d that in the Kołobrzeg Block the onset of petro leum gener a tion occurr ed at the end of the Silu ria n and the be ginning of the Devo nian. Source rocks in the Gryfice Block reached the early stage of oil gener a tion at the begin ning of the Perm ian and gen era tion pro cesses were com pleted by the end of the Trias sic. Migra tion of hy drocar bons from source rocks be gan in the Carbon ifer ous in both the Gryfice and Kołobrzeg blocks and lasted to the end of the Meso zoic. During hydro car bon migra tion, an inten sive disper sion process was observe d, caused by leaking along the fault planes. The mod elling reveale d that hy drocar bons may have ac cu mu lated in De vo nian res er voirs. The lack of any dis cov ered ac cu mu la tions could be the re sult of hy dro car bon dis per sion caused by tec tonic de for ma tion and in tense ver ti cal fault block move ments. Paweł Kosakowski and Magdalena Wróbel, Fac ulty of Ge ol ogy, Geo phys ics and En vi ron mental Pro tec tion, AGH Uni ver sity of Sci ence and Tech nol ogy, Mickiewicza 30, PL-30-059 Kraków, Poland, e-mail: [email protected]; Paweł Poprawa, Pol ish Geo log i cal In sti tute – National Research In stitute, Rakowiecka 4, PL-00-975, Warszawa, Poland, e-mail: [email protected] (re ceived: De cem ber 21, 2009; ac cepted: April 8, 2010). Key words: Gryfice and Kołobrzeg blocks, lower Paleo zoic, source rock, burial history , therm al evolu tion, petro leum processe s. INTRODUCTION shore L2-1/87 and K1-1/86 bore holes were used for mod el- ling of the hy dro car bon gen er a tion and ex pul sion pro cesses (Fig. 1). Mod el ling of hy dro car bon mi gra tion and ac cu mu la- tion was perform ed along the regional 81032K-820 cross-sec - Char ac ter istics of lower Paleozoic source rocks in the Pom - tion (Fig. 1). era nian segm ent of the Trans-Eu ropean Su ture Zone (TESZ) To deter mine the thickness of strata rem oved during the late and the petro leum proces ses in the offshore part of this area Paleozoic and Me so zoic, mea sured pa ram e ters of kerogen ther - were ex am ined. mal ma tu rity were used. The same data were used to model cal - The study area is the offshore parts of the Gryfice and ibra ti on of heat flow changes through time. Having the therm al Kołobrzeg blocks, locat ed in the Pom era nian segm ent of the and burial his tory con strained, the fol low ing ba sic gen er a tion Trans-Euro pea n Su ture Zone (TESZ). Owing to few geologi c condi ti ons were estab li shed for each borehole: data avail able from the lower Pa leo zoic suc ces sion, as well as – time and depth identi fica ti on of the or ganic matter ther - a lack of rep re sen ta tive re sults of geo chem i cal anal y ses for mal ma tu rity in ter vals; the poten ti al source rocks (only Caradocian shales were sam- – po si tion of gen er a tion stages and de gree of kerogen pled), the in ves ti ga tion has the char ac ter of a gen er a tion test. trans for ma tion; Char ac ter istics of source rocks of the lower Pa leo zoic strata – amount of gen er ated and ex pelled hy dro car bon mass; and the model of kineti c transfor m ati ons were adopted from – time and range of hy drocar bon migra ti on; the pe tro leum anal y sis of co eval strata in the Bal tic re gion fur - – time and amount of accu m u lati on. ther east. Re con structed lithostratigraphic sec tions in the off- 184 Paweł Kosakowski, Magdalena Wróbel and Paweł Poprawa Fig. 1. Geo log i cal map of the Pom era nian part of the Cal edo nian Plat form without Perm ian and youn ger de pos its (af ter Pokorski and Modliński, 2007, modified) with lo ca tion of the bore holes ana lysed GEOLOGICAL SETTING that already recog nized in the south ern Skania outcrops. The base ment of the Rugia, Wolin, Gryfice and Kołobrzeg blocks is either re lated to the East Eu ro pean Craton or to ter rains The study area is a part of the northern seg ment of the accreted to the TESZ dur ing the Cal edo nian col li sion. TESZ, lo cated be tween two major fault zones, the Trzebiatów The geo log ical de vel op ment of the area in early Pa leo zoic in the west and the Koszalin in the east (Fig. 1). The lower Pa- time was recon struc ted mainly based on stud ies of the lower leozoic strata are tectoni cally deform ed, folded and most prob- Pa leo zoic sed i men tary rocks in the nearby Koszalin–Chojnice ably also detac hed from their origi nal basem ent (Dadlez, Zone (see Znosko, 1965; Teller and Korejwo, 1968; Dadlez, 2000). Ac cord ing to Pokorski and Jaworowski (2002), in the 1978; Podhalańska and Modliński, 2006; Poprawa, 2006). In Kołobrzeg Block, beneat h the overthrusted lower Pa leo zoic the study area and its east ern vi cin ity the Or do vi cian strata, allochthonous strata, an autochthonous sedi m entar y cover of most fre quently the Llandeillian–lower Caradocian, were the East Euro pean Craton (EEC) might be ex pected, simi lar to found in the bottom part of the boreholes : Brda 2, Brda 3, Hydrocarbon generation/expulsion modelling of the lower Paleozoic potential source rocks in the Gryfice and Kołobrzeg blocks 185 Chojnice 5, L2-1/87, Jamno IG 1, Jamno IG 2, Karsina 1, THERMAL EVOLUTION Kościernica 1, Miastko 1, Nowa Karczma 1, Nowa Wieś 1, Sarbinowo 1, Skibno 1 and Wyszebórz 1 (Dadlez, 1978; Podhalańska and Modliński, 2006; Fig. 1). The folded Silu ria n The late Permian–Me so zoic stage of the study area’s ther - strata were en counter ed in the boreholes : Chojnice 3, mal his tory is rel a tively well un der stood, while the late Pa leo - Klosnowo IG 1, Kłanino 3, Lutom 1, Nicponie 1, Stobno 1 zoic ther mal his tory is less well doc u mented, de spite the ex is - (S 1), Stobno 2, Stobno 3 (S 3), Wierzchocina 1 and tence of geo chemi cal data. The early Paleozoic stage is poorly Wierzchocina 4 (Dadlez, 1978; Podhalańska and Modliński, rec og nized with little in for ma tion. 2006; Fig. 1). Recon struc tion of the heat flow during the geolog i cal evo- The depth of re cent burial of the lower Paleozoic strata lu tion of the ba sin started with anal ysis of the re cent ther mal ranges betwe en 4000 and 7000 m. The lower Paleozoic strata, regim e. The input data consis ted of a map of tem pera ture s for folded dur ing the Caledo nian orog eny (Znosko, 1965; Dadlez, the top of the Zechstein Main Do lo mite car bon ates, i.e. the 1978; Żaba and Poprawa, 2006), is overlai n by a Devo - best recog nized strati graphic hori zon of the study area nian-Car bon ifer ous cover which is presentl y over 1000 m thick (Karwasiecka, 2000). The recon struc tion was based on di rect (Matyja, 2006) and which was also was de formed during the mea sure ments in bore holes in ther mal equi lib rium con di tions Variscan orogeny . In the vicin it y of the Sarbinowo and west of sim ilar to steady-state. Where there was an ab sence of such the Dygowo–Białogard Fault Zone, lower Perm ian ex trusive mea sure ments, the downhole tem per a ture was as sessed be low rocks are pres ent, being a final result of the Variscan orogeny , the observe d ho rizon on the basis of publi shed data on the and which are covered by strata of the upper Rotliegend.