Challenges for Offshore Exploration in Croatia
Exploration of the Croatian side of Adriatic offshore was mostly carried out by INA as exclusive license holder over the area of more than 50000 sq km. From the early sixties a total of 129 exploratory wells have been drilled, 28000 km of 2D and 5700 sq km of 3D have been acquired. The only proven and producing hydrocarbon system is Pleistocene biogenic gas in North Adriatic, however a numerous oil and gas shows have been observed in Central and South Adriatic wells. Geochemical analysis revealed 2 distinctive families of oil attributed to Triassic and Cretaceous sources with more evidences of the immature to early mature Cretaceous kerogens.
INA past exploration efforts were focused on Adriatic Carbonate Platform (ACP) structures while only few attempts were made to investigate deeper, Middle Triassic carbonate-evaporite succession. Therefore, diverse gas and oil plays like Dinaric foreland turbiditic system, ACP margin and South Adriatic Basin structures have not been addressed with historic drilling.
Rather disappointing results of “oil” drilling campaign in the seventies and eighties led to a reduction in capital investment. Last significant seismic campaign took place in 1989, leaving the “hiatus” in seismic activities until the end of 2011. New 2D and 3D seismic in Central and southernmost Adriatic sheds the light on Adriatic Carbonate Platform vs. South Adriatic Basin relationship and enables introducing the variety of new ideas and plays. Testing some of those plays would require exploration drilling beyond 800 m water depth.
Fair to poor seismic imaging and capabilities of drilling in maximum water depth of 350m were key constraints which blocked the fairway to success in the past. Today, when qualitative shift is made in technical direction, changing legal and fiscal environment and exploration permits shortage represent major challenges for INA offshore exploration in Croatia.
AAPG Search and Discovery Article #90161©2013 AAPG European Regional Conference, Barcelona, Spain, 8-10 April 2013