Galilee Energy (ASX:GLL) has identified a significant expansion of the drilling target inventory at its Zydeco oil and gas project in Louisiana, and now plans to test the upside through a sidetrack of the Zydeco-1 well, which has been redesigned to evaluate seven separate oil and gas targets from a single wellbore.

Five shallow targets identified through the drilling of the Zydeco-1 well have been estimated to contain a combined gross prospective resource of 317 thousand barrels (kbbl) on a 2U basis and 422.6 kbbl on a 3U basis, materially increasing the number of potential hydrocarbon-bearing intervals available for evaluation during the sidetrack.

That broader target stack matters because it gives the company more than one interval to assess within the same lease position, while also building on data gathered from the original well rather than starting with a fresh location. For a project in a mature onshore basin, the value of that additional subsurface information is often in how it sharpens the next drilling decision and reduces uncertainty around where to evaluate hydrocarbons.

"The original Zydeco well has given us substantially more information than we had before drilling," Managing Director Joseph Graham said.

"The sidetrack is now designed to capture that value by testing a broader, stacked target inventory from the shallow oil zones through Stafford and into the Upper Tweedel.

"The new shallow-zone resource estimate adds another dimension to Zydeco. We now have five prospective oil intervals above Stafford and Tweedel, all within the same compact lease position and close to existing Gulf Coast infrastructure.

"Our immediate focus is to finalise the sidetrack design and evaluation program so that if we encounter movable hydrocarbons, we will collect the pressure, fluid and petrophysical data needed to make a disciplined commercial decision."

The five shallow targets — Borsum, Richie, Discorbis gravelli, First Het and Homeseeker B — were identified from original-hole logging-while-drilling (LWD) data. The five zones have been assessed using seismic interpretation together with data from the MacCabees-1, J.D. Sittig #1 and regional wells.

The proposed sidetrack is intended to preserve and re-evaluate the five shallow intervals before continuing down to the Stafford level at approximately 9,391.5 ft TVD and the Upper Tweedel at approximately 9,579.5 ft TVD.

The exact kick-off point, trajectory, casing design and final total depth all remain subject to final drilling-engineering approval.

Prior to markets opening, GLL was steady at 0.4¢ with a market capitalisation of $7.245 million.