Run by oil and gas entrepreneur Tom Cross, Parkmead believes Pharos has the potential to contain up to 500 billion cubic feet of gas-in-place close to an existing find.
Success with the well could provide a big boost for Mr Cross's attempt to build another big North Sea oil and gas business at Parkmead.
Mr Cross made £57m when the Dana Petroleum business he built was bought by Korea National Oil Corporation for £1.9bn in 2010.
Parkmead started work on the Pharos well soon after completing the £15m acquisition of Lochard Energy, which Mr Cross described as its biggest move to date.
Mr Cross said, if successful, Pharos could add significant further value to the nearby Platypus gas field and greater understanding of the Blackadder prospect. He said: "Parkmead's portfolio is growing rapidly, giving Parkmead a balanced asset base of production, development, appraisal and exploration opportunities."
Shares in Parkmead Group closed up 0.625p at 11.875p. Dana Petroleum is the operator of the Pharos well with a 35% stake. Parkmead holds a 20% working interest.
It said the other joint venture partners are Dyas Exploration UK and MPX North Sea.