The investors in the Horse Hill-1 well being drilled just two miles away from Gatwick Airport were cautiously optimistic following the completion of the latest phase of work.
However, they must wait another week before results from the Jurassic reservoir sections are logged and interpreted.
The well has been drilled to 6,612 feet, which is deeper than first expected for this phase.
This results from the fact a number of reservoir intervals identified are deeper and thicker than expected.
As previously announced, oil shows from mud logging were identified in the Portland Sandstones.
Today it was revealed oil shows, mineral fluorescence and elevated gas readings were observed from intervals C1 through to C5 during the latest drilling phase.
The significance of these hydrocarbon shows will only become clear following the analysis of the detailed down-hole electric logs, said AIM-listed Solo Oil (LON:SOLO), one of the investors in the project.
Solo director Neil Ritson said: "We look forward to the analysis of the electric logs through the Jurassic interval where reservoirs and oil shows have been observed whilst drilling.
“The commercial significance of those will be assessed when all relevant data has been analysed.
“The well is now expected to be deepened to the Triassic in order to explore for further reservoirs, anticipated to be gas charged, at a depth rarely tested so far in the Weald Basin."
Once the detailed logging is complete the plan is to drill down to test the Triassic aged rocks from deeper lying gas.
The licence is 65% owned by special purpose vehicle called Horse Hill Developments Ltd (HHDL), which is operator, while Magellan Petroleum Corporation has a 35% interest.
However, Solo and Regency Mining (LON:RGM) recently acquired 10% and 5% respectively.
And they aren’t alone in the venture, which also features as HHDL stakeholders David Lenigas’s UK Oil & Gas Investments (LON:UKOG), Stellar Resources (LON:STG), Doriemus (LON:DOR) and Alba Minerals (LON:ALBA).