Galilee Basin

The Galilee Basin is an onshore basin located in central Queensland and covers an area of ~247,000 km2. It lies adjacent to two major producing basins in the Bowen and Cooper basins. The Galilee Basin is prospective with 107 deep exploration wells drilled since the 1950’s. No economic discoveries have been made to date from this limited exploration, however, numerous oil and gas shows have been encountered. These shows, including in the Lake Galilee Sandstone, are an indication that an active petroleum system exists.

The basin is near the proposed extension of Jemena’s Northern Gas Pipeline from Mt Isa to Roma as well as the recently sanctioned Adani coal mine, which may require gas to power its operations.

ATPs 743P, 744P and 1015P (Deeps), Koburra Trough, Galilee Basin

  • Vintage Energy Ltd – 30% 
  • Comet Ridge Ltd - 70% (operator)

Recent events

Recent weather events have delayed the Albany Field appraisal program. It is anticipated that once the area is accessible, which is expected around May 2020, the program will recommence.  The first planned activity will be the stimulation of Albany-1 ST1 which is expected to be followed by the flow testing of both Albany-1 ST1 and Albany-2.

Summary

Vintage signed a farm-in agreement with Comet Ridge Ltd to earn a 30% staged interest in the “Galilee Basin Deeps Joint Venture” to investigate reservoir sequences of the Galilee Basin within permits ATP 743, ATP 744 and ATP 1015.

Koburra Trough, stratigraphic column image +

 

The joint venture is focused on the ‘Deeps’ within each of the Petroleum blocks, which is defined as including all strata commencing underneath the Permian coals (Betts Creek Beds or Aramac coals) with the main target being the Lake Galilee Sandstone sequence. The technical and commercial work undertaken by Comet Ridge has highlighted the potential of this largely ignored Galilee Basin sandstone conventional gas target. Gas has already been discovered in the Galilee Basin and, with future appraisal success, the basin could quickly become a significant contributor to the East coast gas market.

Vintage, through a two-stage farm-in, has earned a 30% interest in the ‘Deeps’  within ATPs 743P, 744P and 1015P by paying 100% of the cost of the Albany-1 well, up to a cap of $3.35 million, 50% of the cost of the Koburra 2D seismic survey and 50% of the drilling of Albany-2 and Albany-1 STI, up to a cap of $10 million (gross). Comet Ridge has 100% interest in the ‘Shallows’ (the coal targets that generally range from approximately 600 metres down to 1,100 metres).  Full details of the farm-in conditions and stages are provided in the ASX release dated 1 November 2017.

The area is lightly explored with little seismic and only three deep wells drilled within the permits. However, the Lake Galilee Sandstone sequence has flowed gas to surface from Lake Galilee-1 (1964) and Carmichael-1 (1995), which were drilled targeting oil. The application of the latest technology and the utilisation of air/nitrogen drilling has already resulted in successful flow of gas to surface through Albany-1.

Carmichael-1 is considered to have made a gas discovery and a Contingent Resource for the underlying large 61 km2 Albany structure has been booked by Comet Ridge. It has been assessed by independent experts to contain a conventional gas Contingent Resource as shown in Table 1. Via the farm-in process, Vintage has earned its proportional share of the Contingent Resource for the Albany structure.

Table 1: ATP 744 Independent Resource Certification for the Albany Structure

*COI ASX announcement 5 August 2015, ATP 744, independent resource certification, Carmichael Structure.
Conventional Gas Contingent Resource*
(PJ)
Equity 1C 2C 3C
100% 56 153 417
30% 17 46 125

The Contingent Resources for the Albany (Carmichael) structure referred to in Table 1 are taken from an independent report by Dr. Bruce McConachie of SRK Consulting (Australasia) Pty Ltd, originally released to the market in Comet Ridge’s announcement of 5 August 2015. Estimates are in accordance with the Petroleum Resources Management System (PRMS) (SPE, 2007) and Guidelines for Application of the PRMS (SPE, 2011).  Probabilistic methods were used. Following the drilling of the Albany-1 well, SRK is of the view that the measured gas flow rate endorses their previous estimate of the range of Contingent Resources.

The key to unlocking this potentially valuable resource is obtaining a commercial flow rate. The staged work program is designed to address this issue on the Albany structure and further define other opportunities around the permits. The program commenced in May 2018 with the drilling of one conventional gas appraisal well (Albany-1) on the Albany structure, close to where the Carmichael-1 well flowed gas in 1995. The well was designed so that the prospective section would be drilled with air/nitrogen rather than conventional drilling mud, to enhance the potential flow rate from the sandstone. Vintage funded the first $3.35 million of this stage (Stage 1a) to earn a 15% interest in the “Deeps” across the three Galilee permits.

The well was drilled to a depth of 2,595 mKB and penetrated 13 metres of the “B” sand which flowed gas continuously for 23 hours. The flow was diverted to the testing equipment where a stabilised rate of 230,000 scf/day was measured over a period of 1.5 hours through a 1¼” orifice plate, with no formation water recovered.

The operator, Comet Ridge, released an ASX statement dated 28 June 2018, regarding the status of Albany-1. Comments from the Managing Director include:

  • "We are extremely pleased with the initial flow rate at the Albany-1 well, which has been achieved from a 13 metre interval, which represents approximately 10% of the sandstone interval targeted by the well”;
  • “Very poor gas flow rates from ... older wells were due largely to the way they were drilled, not the underlying reservoir geology”;
  • “... the best option to finish this well is to use a larger rig and undertake that work with the drilling of Albany-2”: and
  • “The joint venture is now actively planning the location of the step-out Albany-2 well …”.

On 30 December 2018, Stage 2 of the farm-in commenced with the 336 kilometre Koburra 2D seismic program across permits ATP 743, ATP 744 and ATP 1015.

The seismic program delivered two main outcomes.  It firstly matured Lake Galilee sandstone leads and prospects, some to drillable status and also defined the highly prospective regional structural trends with multi-level targets. 

A successful, two well, appraisal drilling program was then completed with the drilling of the Albany-2 and Albany-1 ST1 wells.  With the drilling of Albany-2 and the side-track of Albany-1 through the entire reservoir section, the joint venture set out to:

  • Confirm the Albany Field structural mapping
  • Confirm the presence of gas seven kilometres to the south east of Albany-1 via an aggressive step-out
  • Assess the continuity of the reservoir sands
  • Investigate any variation in reservoir quality
  • Acquire core to aid with stimulation design
  • Acquire core to investigate sensitivities to drilling fluid components

The joint venture was pleased that all the above objectives were met as detailed in the various categories below.

  1. Structure: Albany-2 was drilled as a seven kilometre step out to the south east of Carmichael-1 and Albany-1, with initial interpretation indicating that the Lake Galilee Sandstone was penetrated some 25 metres up-dip of Albany-1 ST1, consistent with pre-drill mapping.
  2. Presence of gas across the structure: Log analysis at Albany-2 calculates gas in multiple sands of the Lake Galilee Sandstone reservoir section. 
  3. Continuity of reservoir sandstones: The reservoir sandstones extend across the Albany Field, with some stratigraphic variation observed mainly in the A and B sands.  Despite the reduction in sand content within the A interval at Albany-2, there is still around 140 metres of gross sandstone within the B, C and D intervals. 
  4. Variation in reservoir quality: Log analysis at Albany-2 shows maximum porosities up to 15%.   Over small intervals this is in excess of those calculated at the Carmichael-1/Albany-1 ST1 location, providing potential upside for gas in place and flow potential.
  5. Core for stimulation design: A total of 62 metres of core was acquired in Albany-2.  X-Ray Diffraction (“XRD”) analysis has been undertaken on cored reservoir samples. This examines the constituent minerals of the rock to assist with the chemical selection for the stimulation fluid. Capillary suction testing will also be carried out to select the stimulation fluid that will provide the best outcome for flowing gas through targeted reservoir sandstones. 
  6. Core for drilling fluid design: A program of testing will be designed to study how various drilling mud components may interact with the reservoir rock to inhibit flow (i.e. what are the potential damaging mechanisms for this reservoir). This data will be used for either designing optimal drilling fluids or to consider whether a mud system should be used versus an air/nitrogen underbalanced system.
  7. Conventional core analysis: Core porosity and permeability data will be used to calibrate log analysis for these reservoirs.
  8. Gas shows in Albany-1 ST1: Albany-1 ST1 showed excellent gas shows in the B sand section that flowed gas to surface at 0.23 MMscfd from Albany-1.  Shows of equal and better magnitude were evident in multiple sands not penetrated in Albany-1, offering encouragement for what a flow test of the full reservoir section might offer post-

The next steps in the evaluation of the Albany Field will be to stimulate the reservoirs (Albany-2 already stimulated) and flow-test both Albany-1 ST1 and Albany-2, to demonstrate the potential commercial viability of the wells. Stimulation of similar quality reservoirs in the Cooper Basin is common-place.  For Albany-1 ST1, the whole reservoir section is cased and available for stimulation.  With log analyses and gas shows indicating the presence of gas in each of the A, B, C and D sand units, it is expected that these will all be stimulated with at least one stage each. 

Albany-1 ST1 and Albany-2 will be the first wells to be stimulated in the Lake Galilee Sandstone of the Galilee Basin, and it is likely there will be optimisation of the stimulation approach based on the outcomes from these first two wells. Once stimulation has been completed at Albany-1 ST1, the well will be flowed back in a controlled manner, similar to Albany-2, to enhance the recovery of stimulation and drilling fluids to maxmise the subsequent potential gas flows.  The plan at this stage is to run a Production Logging Tool (“PLT”) once the wells are flowing to assess the contributions from each of the sand sections.

Vintage Energy

Vintage Energy Ltd has been established to acquire, explore and develop energy assets principally within, but not limited to, Australia, to take advantage of a generally favourable energy pricing outlook.

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