engleski

View on Potentially Hydrocarbon Bearing Deposits in Dinaridic Area, Implicated to Positivity of Adriatic-Dinaridic Platform Sediments and their Bottom

Abstract: Whole Dinaridic area, including External and Internal Dinarids, considered as unique geodynamic and genetic entity, is the part of ancient Adriatic-Dinaridic Carbonte Platform (ADCP). In the palegeographic sense, this Platform was representing an object or body, generated by deposition of carbonate sediments in relatively shallow sea. This process started approximately before 190 Ma, in Early Jurassic, and finished by ending of carbonate sedimentation, generally in Late Middle Eocene (Late Lutetian), when tectonic postlaramian movements caused forming of Flysh basin, and when clastic sediments started to generate. Adriatic-Dinaridic Carbonte Platform (ADCP) was surrounded by deep ocean Tethys, covering, by comparing to present, whole Mediterranean region and more toward east. Looking such accommodation space and corresponding processes, there were for sure favorable conditions for generating hydrocarbon reservoirs, and different traps, what was proved by plenty of commercial discoveries. During twenty years (1959-1979.) in Dinarides, in fact at ADCP, total 19 exploratory wells were drilled. The most significant appearances of hydrocarbons were related to transitional zone of Anhydrite-Carbonate Complex (ACC) and deeper, stratigraphically ranging, generally from Upper part of Triassic (related to anhydrites), to the time span from Early Jurassic to Late Middle Eocene (related to carbonates, concerning end of carbonate platform sedimentation), which means “ to the bottom of the ADCP, sensu lato” . Because of reservoir characteristics of these sediments, many technical problems and difficulties were appeared while drilling. One of the most important is mud infiltration in wellbore zone, causing damage, and it’ s prevention is very important task. In the case when caverns are infilled with mud fluid, testing results could show incorrect parameter, logically leading to wrong conclusions. By synthesis of obtained well testing results at ADCP and it’ s bottom, and comparing them with the production experiences from wider Mediterranean area (comparable geological provinces), it is necessary to apply acquired experiences and new solutions due to prevent and solve such problems. Concerning very low exploration range and insufficient area covered with explorations, it is necessary to involve more complex approach to this problematic. Using newest technical methods, we expecting approve of potentially hydrocarbon saturation, and finally as a result beginning of development activities. Sažetak: Područje Dinarida, kako Vanjskih tako i Unutarnjih, koje treba promatrati kao jedinstvenu geodinamsku i genetsku cjelinu, dio je drevne Jadransko-Dinaridske karbonatne platforme (Adriatic– Dinaridic Carbonate Platform, ADCP), koja u paleogeografskom smislu predstavlja tijelo nastalo taloženjem karbonatnih sedimenata u relativno plitkom i toplom moru. Ovaj proces je počeo prije približno 190 milijuna godina u starijoj juri, a završio je prestankom karbonatne sedimentacije, generalno krajem srednjeg eocena, kada je tektonskim postlaramijskim pokretima formirano flišno korito i kada su otpočeli ciklusi generiranja klastita. Navedenu platformu (ADCP) je okruživao duboki ocean Tethys, koji se pružao s današnjeg gledišta preko cijelog Mediterana i dalje na istok. Na takovom sedimentacijskom prostoru su bez sumnje stvoreni uvjeti za generiranje naftnih i plinskih ležišta, a tektonikom i zamki, što je potvrđeno brojnim komercijalnim otkrićima. U periodu od 20 godina (1959-1979.) u području Dinarida, odnosno Jadransko-Dinaridske karbonatne platforme izgrađeno je 19 istražnih bušotina. Najznačajnije pojave ugljikovodika između ostaloga, bile su vezane za graničnu zonu anhidritno-karbonatnog kompleksa naslaga (ACC) i dublje, čiji je stratigrafski raspon generalno od mlađeg dijela trijasa (vezano za anhidrite) do raspona starija jura-kasni srednji eocen (vezano za karbonate, ako se govori o kraju platformne karbonatne sedimentacije), dakle za ˝podinu ADCP-a, sensu lato˝. Zbog ležišnih karakteristika tih sedimenata, pojavljuju se brojni problemi pri bušenju, a jedan od glavnih je oštećenje pribušotinske zone prilikom izrade kanala bušotina, te je njegovo sprječavanje vrlo važan i zahtjevan zadatak. Ukoliko se postojeće pukotine tih sedimenata zapune radnim fluidom, može tijekom ispitivanja izostati pozitivni rezultat, koji dovodi do pogrešnih zaključaka. Sintezom polučenih rezultata putem ispitivanja bušotina Jadransko-Dinaridske karbonatne platforme i njezine podine, kao i usporedbom s iskustvima proizvodnje iz šire, mediteranske regije (a s usporedivih geoloških provincija), treba primijeniti stečena iskustva i nova rješenja kojima bi se onemogućili i spriječili takvi problemi. Isto tako, s obzirom na mali stupanj istraženosti, i nedovoljno veliki prostor koji je bio pokriven istraživanjem, potreban je kompleksniji pristup ovoj problematici, kako bi se suvremenim tehničkim metodama došlo do spoznaja o potvrdi potencijalne naftnoplinonosnosti razmatranog područja, a time i početka razradnih aktivnosti.

Hydrocarbon Baring Deposits; Dinarids; Adriatic-Dinaridic Carbonate Platform; Problems While Drilling; Reservoir Characteristics

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