Podzemno skladište plina d.o.o. (Underground gas storage Ltd.)

Gas storage is an integral technological and business activity of each gas system, and underground gas storage facilities are fundamental for security and flexibility of supply. At the moment Croatia has got only one underground gas storage facility in Okoli, 50 km southeast of Zagreb, and it is currently managed by the national storage system operator - Plinacro's daughter company Podzemno skladište plina d.o.o.

Underground Gas Storage Okoli was put into trial run at the end of 1987, while in April 1988 the first cycle of gas injection began. After more than 20 years of doing business within INA, the Underground Gas Storage Okoli was organized as
Podzemno skladište plina d.o.o. at the start in early December 2008. On 30 January 2009, after signing the Agreement for the sale and purchase of business shares in Podzemno skladište plina d.o.o. with INA, Plinacro acquired a 100% share in the company, the main activity of which is natural gas storage.
Apart from its core business of natural gas storage, PSP d.o.o. is responsible for management, maintenance and development of a safe, reliable and efficient gas storage system, as well as for further development of storage capacities and storage operations. Croatia will improve the safety of the gas system of our country by carrying out development plans and new investment cycles of PSP, that is, by modernization and expansion of the compressor of the existing storage facility in Okoli and the construction of a peak gas storage facility in Grubišno Polje, as well as a future strategic underground gas storage facility.
Technical characteristics of PSP Okoli:
The Okoli underground gas storage facility (PSP) is located in Velika Ludina in Sisak-Moslavina County. 
Technical characteristics: 
• operating volume: 438,000,000 m3 of gas
• maximum continuous capacity of gas withdrawal from the storage facility (Qmaks. pov.) = 240,000 m3/h (5.76 × 106 m3/day)
• maximum continuous capacity of gas injection into the storage facility (Qmaks. ut.) = 180,000 m3/h (4.32 × 106 m3/day)
• minimum capacity of gas withdrawal from the storage facility (Qmin. pov.) = 20,000 m3/h
• minimum capacity of gas injection into the storage facility (Qmin. ut.) = 27,000 m3/h
• maximum allowed dynamic pressure at the mouth of the well during injection: 190 bar
Pressure of the facility (entry/exit) at the point of entry into the transmission system:
• minimum: 25 bar
• maximum: 45 bar
Considering that PSP Okoli is a seasonal storage facility, the technological process is carried out in two cycles:
injection cycle that lasts from 1 April to 30 September (± 30 days) and 
withdrawal cycle that lasts from 1 October to 31 March (± 30 days).  
Connecting to the transmission system: PSP Okoli, Naftaplinska 10, Velika Ludina, Republic of Croatia.