The Australia-listed company, formerly known as Clean Global Energy, said the well was drilling ahead at 862.6 metres following a bit change.
Drilling is expected to reach the primary C18 and C19 reservoir targets, at a depth of about 1219.2 metres, in about 10 to 15 days.
Citation stated that oil and gas shows were encountered over a 15.24-metre section in the C14 carbonates, from limestones and vuggy dolomites.
Numerous samples from the interval indicated up to 50% oil saturation, the company said.
In addition, current structural interpretation has indicated that the Atzam-4 well formation tops are being intersected about 91.44 metres higher than the productive Atzam-2 offset well, which lies about 500 metres to the west.
Following the completion of a flow testing programme on Atzam-4, the Atzam-5 well is expected to spud, Citation said.
Atzam-4 is located in Block 1-2005 in the South Peten basin of Guatemala.
Citation is the majority holder of Block 1-2005, as well as Block 6-93, through its 70%-owned subsidiary, Latin American Resources.
The two blocks have been estimated to hold proved plus probable reserves of 2.3 million barrels of oil.