Exploration and Appraisal
Rafael Gas and Condensate Discovery (BURU 100% EP 428 & 60% EP 457 AND OPERATOR)
The Rafael 1 well is located in Exploration Permit 428 in the Canning Basin, some 50 kilometres to the east of the Ungani Oilfield and some 150 kilometres east of Broome. The well was drilled in late 2021 and production tested in early 2022 after encountering gas in several zones.
The flow testing program undertaken during the year over the lower open hole part of the interpreted gas bearing Ungani Dolomite section returned very positive results with constrained flow rates of up to 7.6 mmcsfd with high condensate content of ~40 barrels per mmscf and low level of inerts.
The overall gas composition has several significant benefits. In particular, the low level of CO2 means that there is no need for additional high-cost processing infrastructure to reduce the level of carbon dioxide in the gas prior to its sale or use, and as a result there should be no requirement for separate disposal of reservoir contained CO2. The CO2 content is very low compared to other natural gas reservoirs in Western Australia and there will be substantial emissions reduction benefits accrued during production of the resource.
Several areas of anomalous hydrogen concentrations were also noted during the drilling of the well and these will be further investigated as part of the ongoing analysis of the results from the well.
Initial analysis of the pressure data indicates that there is no evidence of reservoir depletion or reservoir boundaries within the radius of investigation of the flow test. This is very encouraging for assessment of the resource volumes, but longer test durations will be necessary to determine the limits of these parameters.
Most importantly, the reservoir pressure of some 6,200 psi measured from the static gradient survey indicates that there is potential for a substantial gas column to continue downdip from the gas column intersected in the well. This gas column is interpreted to be potentially at least down to the extent of the currently interpreted structural closure which is mapped by Buru from the existing 2D seismic data to be up to 700 metres of vertical closure. There are a number of factors that could influence this calculation and further appraisal drilling will be required to identify the position of the gas/water contact and the extent of the gas column, and hence to confirm the potential resource volumes.
The other indication from the interpretation of the pressure data is that there is apparent near wellbore effects from invasion by drilling and completion fluids that has reduced the flow capacity of the tested zone. Experience in similar reservoirs indicates that this form of reservoir effect can be remedied by standard workover operations.
Rafael Appraisal Program
During the year, preparations were completed for the acquisition of a 3D seismic survey over the Rafael structure, and a further flow test of the Rafael 1 well, as part of a systematic appraisal of the discovery.
These activities were curtailed by the change of strategic direction by Origin Energy, Buru’s 50% partner in the project. Subsequent to Origin’s exit from the joint venture in January 2023 the seismic acquisition program is now planned for mid-2023.
Independent Resources Review
Subsequent to the successful flow test of the well, ERCE Australia Pty Ltd (ERCE), a specialist resource assessment consulting group, was commissioned to undertake an independent assessment of the gas and liquids resources of the Rafael 1 discovery.
The assessment incorporated the technical evaluation of the Rafael 1 well results and the subsequent flow test of a limited part of the interpreted hydrocarbon column in the well.