Longtom-3 ST1 intersected 98m of gross gas sand (vertical thickness) over 414m interval in the Admiral Formation.
Nexus said these intersections, combined with those in the pilot hole, had confirmed its geological model for the Longtom field.
“The results to date are very encouraging,” managing director Ian Tchacos said.
“The Admiral reservoir intersections in the pilot hole and in the sidetrack well have provided sufficient confidence in our geological interpretation to proceed with the horizontal section of the well as originally planned.”
The company will now start the planned horizontal section of the well, which is expected to lead to completion and production testing.
Following the successful drilling of the Longtom-3 PH, the well was plugged back to the casing shoe at 995m and the sidetrack well drilled. This sidetrack was drilled as a deviated well and will also be plugged back to 2380m before the horizontal well is drilled laterally through the Longtom gas sands and tested as planned.
The sidetrack was drilled to intersect the reservoir sands in a crestal position to provide additional data on sand quality and lateral continuity.
Based on wireline log and pressure data, the individual sands – including the sands that were cored but not successfully tested in Longtom-2 – are interpreted to be laterally continuous between all Longtom wells, while also being vertically isolated from each other.
Looking ahead, Nexus plans to run casing across the upper gas reservoirs in Longtom-3 ST1 and also to drill the well horizontally through the lower gas sands. The company expects the horizontal section of the well will provide further information about the quality and lateral continuity of the lower Admiral reservoirs.
Once the horizontal section is drilled, the well is expected to be completed, with the upper and lower sands tested to confirm the productivity of the key gas zones. Upon completion of a successful production test, the well will be suspended as a future producer, Nexus said.
“We have been able to take advantage of advanced seismic processing techniques [seismic amplitudes] to determine the quality and distribution of the thicker gas-filled sands in the section,” Tchacos said.
“This has positive implications for optimising the horizontal part of this well and the placement of future wells.
“I am particularly pleased about our ability to properly evaluate both well bores with down hole logs and formation pressure measurement tools. This additional information is key to refining our understanding of the Longtom field’s resource potential.”
To date, 1568m of new hole has been drilled in Longtom-3 ST1, and at the present depth of 2563m, the bottom hole location is 1050m from the Longtom-3 PH bottom hole location and 800m from Longtom-2 bottom hole location.
Longtom-3 is part of a sole risk appraisal program operated by Nexus, which has increased its best estimate of the Longtom gas field by 38% to 438 billion cubic feet of possible gas reserves.
Apache Northwest, which has a 62.5% interest in Vic/P54, has a right to buy back into the field development following the drilling of Longtom-3 by paying Nexus six times the cost of its share of the project, plus back costs associated with its share of the program.
In December, Nexus signed a gas sales and processing agreement with Santos for up to 450 petajoules of gas from Longtom. The two companies have now started front-end engineering design studies on the project, with the aim of making a project sanction decision in the fourth quarter of this year.