Madalena's partner and operator on the block, PAE kicked off work in March, and drilled for around 1,000 metres horizontally at a depth of approximately 3,200 metres.
The well, dubbed CAS.X-15, which was completed at the end of May, has tested an average of 430 barrels of oil per day through three-millimetre choke for the last four weeks.
Madalena chief executive Jose David Penafiel said the well test results were "extremely encouraging" and the firm was now looking forward to increased production revenue as a result of this new well.
"The well results of CAS.x-15(ST) are significant on a number of grounds.
"It has significantly derisked Madalena's Vaca Muerta acreage in the CASE block, supporting the company's internal contingent resources estimates.
"To obtain these test results from just 1,000 metres and 37 frac stages is clearly satisfying, however, Madalena believes that with further improvements to the drilling and completion techniques, considerably more can be realized from the next wells that will be drilled on the CASE block.
"This result highlights the prospectivity of our Vaca Muerta acreage...," he added.
Madalena holds a 35% working interest in the block, PAE has 55%. Gas y Petroleo del Neuquen, the provincial oil and gas company, holds 10%.
The total gross estimated cost of this re-entry is US8.72mln, which includes the costs for drilling, completing and equipping the well.
The 2017 work program at CASE consists of two well re-entries with a net benefit to Madalena of up to $5.6mln in carried capital costs.
Shares in Toronto were unchanged at 17 cents each...