Evaluation of Mezardere Formation as an Unconventional Shale-Oil Reservoir, Thrace Basin, Northwestern Turkey

Abstract

This study intends to answer the following questions: 1) Does the Lower Oligocene Mezardere shale possess any unconventional hydrocarbon resource potential? 2) What is the predominant hydrocarbon type? 3) Which wells are the sweet spots (if any)? 4) Where is the core area? 5) What is the final OIPE (oil in place equivalent in bbl) resource estimate of the Mezardere? Rock-Eval pyrolysis data from 445 rock samples and 47 wells and other geologic, geochemical and geophysical data from literature were evaluated by Winstat Statistic, PetroMod 11 1D Basin Modeling and Surfer 9.8 software programs. Accordingly, the Mezardere exhibits the following average values that favor its shale-oil reservoir potential: sufficient depth:1924m, type II+III organic matter: HI=186 mgHC/gTOC, sufficient organic richness: TOC=0.87wt.% and sufficient thermal maturity for oil generation:%RoCAL=0.68. Thermal modeling applied to the core area revealed that oil and condensate+wet gas generation commenced at 21 m.a.b.p and 9 m.a.b.p., respectively that is supported by the positive genetic link found between Mezardere shale and oil in Gelindere, wet gas in Degirmenkoy and condensate in Karacali fields. Overall, these findings indicate that Mezardere shale has expelled a portion of its generated hydrocarbons. Signature of retained hydrocarbons in Mezardere may be acquired by using oil saturation index (OSI=S1/TOCx100) which is a recent innovational technique to detect oil saturated productive intervals in shale reservoirs. OSI values over 100 mgOil/gTOC indicate producible oil and natural open fractures in the shale matrix. In the Thrace Basin, the 6 wells (sweet spots) show high to very high OSI values that means 4.25% of the OSI values are greater than 100. This was resulted determination of 15 different oil saturated intervals with an average thickness of 65m. The OIPE prospective reserves of each interval were estimated by taking into account of 40 acre well spacing, individual net oil saturated thickness (m) and total oil content (bbl/m³) as about 3.86 MMbbls (Million barrels). Volumetric prospective reserve estimation of the whole core area (1200km²) where the 6 wells are located resulted that OIPE values of P90, P50 and P10 are 0.04, 1.50 and 45.80 Bbbls (Billion barrels), respectively. Accordingly, mean Swanson OIPE of the core area was computed as the final reserve of 4.5 Bbbls. The results will be compared with those published in EIA April 2011 and June 2013 reports.

AAPG Datapages/Search and Discovery Article #90194 © 2014 International Conference & Exhibition, Istanbul, Turkey, September 14-17, 2014