A.N. Pragt
Please Note
1 records found
1
The geological history of the McArthur Basin (NT Australia) is poorly understood. It consists of five onshore Paleo- to Mesoproterozoic packages with mainly siliciclastic and carbonate rocks, with cumulative thicknesses up to 15km. The basin contains the world’s oldest hydrocarbons, principally hosted in unconventional reservoirs in the Wilton Package. Fluid flow in these reservoirs is related to natural, reactivated or induced fractures. Characterizing the fracture network is an important part of predicting fluid flow. This study tries to link the geological history to the generation of fractures.
The geological history needs to be better understood to characterize the fracture network. In this study seismic, well, outcrop and geophysical data are integrated to construct a cross section that links outcrops (Batten Fault Zone and Broadmere Complex) with the subsurface (Beetaloo Sub-basin). The literature in combination with the cross section is used to revise the geological history.
A fieldwork is conducted to study fracture geometries on outcrops of the Wilton Package that are analogues to subsurface fracture networks. A drone is used to image fracture pavements at an order (102m) that is normally missed by geologists (101m) and satellite images (103m). The Tanumbirini-1 well, located in the sub-basin, provides a FMI log for interpreting fractures in the subsurface. A key objective is to differentiate fractures associated with fracture drivers like regional stress, folds and faults.
This study identified two unconformities in the seismic data, corresponding to two deformation events. The Carpenteria Event between the Wilton Package and the Inacumba Group is associated with a dominantly N-S oriented stress field and the Borroloola Event within the Inacumba Group corresponds to a mainly E-W oriented stress field. Both events created their own fracture sets and are observed on outcrops and in the subsurface. The tectonic stress is σ1 at the surface but σH,max in the Beetaloo Sub-basin. Fracture generation in the sub-basin happened at another stress regime than the surface outcrop analogues, making any direct comparison less reliable. Hence this study gives a prediction of the fracture density and permeability trends in the sub-basin. A conceptual model of the subsurface permeability is proposed where the permeability trend is mainly E-W oriented. ...
The geological history of the McArthur Basin (NT Australia) is poorly understood. It consists of five onshore Paleo- to Mesoproterozoic packages with mainly siliciclastic and carbonate rocks, with cumulative thicknesses up to 15km. The basin contains the world’s oldest hydrocarbons, principally hosted in unconventional reservoirs in the Wilton Package. Fluid flow in these reservoirs is related to natural, reactivated or induced fractures. Characterizing the fracture network is an important part of predicting fluid flow. This study tries to link the geological history to the generation of fractures.
The geological history needs to be better understood to characterize the fracture network. In this study seismic, well, outcrop and geophysical data are integrated to construct a cross section that links outcrops (Batten Fault Zone and Broadmere Complex) with the subsurface (Beetaloo Sub-basin). The literature in combination with the cross section is used to revise the geological history.
A fieldwork is conducted to study fracture geometries on outcrops of the Wilton Package that are analogues to subsurface fracture networks. A drone is used to image fracture pavements at an order (102m) that is normally missed by geologists (101m) and satellite images (103m). The Tanumbirini-1 well, located in the sub-basin, provides a FMI log for interpreting fractures in the subsurface. A key objective is to differentiate fractures associated with fracture drivers like regional stress, folds and faults.
This study identified two unconformities in the seismic data, corresponding to two deformation events. The Carpenteria Event between the Wilton Package and the Inacumba Group is associated with a dominantly N-S oriented stress field and the Borroloola Event within the Inacumba Group corresponds to a mainly E-W oriented stress field. Both events created their own fracture sets and are observed on outcrops and in the subsurface. The tectonic stress is σ1 at the surface but σH,max in the Beetaloo Sub-basin. Fracture generation in the sub-basin happened at another stress regime than the surface outcrop analogues, making any direct comparison less reliable. Hence this study gives a prediction of the fracture density and permeability trends in the sub-basin. A conceptual model of the subsurface permeability is proposed where the permeability trend is mainly E-W oriented.