The Mediterranean nation, which in April kicked off its maiden offshore round, is to put a total of 14,600 square kilometres of acreage on the block.
Economy Minister Ivan Vrdoljak is to unveil the onshore round at a press conference in Osijek on Friday morning.
The six blocks to be put on offer are in the Drava, East Slavonia and Sava regions. Each will be between 2100 and 2600 square kilometres and are located in the proven and producing Pannonian basin.
Interested parties will be able to assess around 700 kilometres of 2D seismic, 1400 square kilometres of 3D seismic and data from 500 wells in the three regions once the data room is open.
In April Croatia put 29 offshore blocks up for exploration with bidders to be offered production sharing contracts of five-year exploration periods and 25-year production period. The blocks cover a total area of 36,800 square kilometres.
Of the blocks on offer, eight are located in the northern Adriatic and 21 in the central and southern part of the sea, with one covering between 1000 and 1600 square kilometres.
More than 40 oil companies have already visited the data room with respect to the offshore round, with bids to be submitted by 3 November.