| Roebuck basin is located in the middle of the northwest continental shelf of Australia,adjacent to the browse basin and the North Carnarvon basin with high degree of oil and gas exploration.It is a new target area for oil and gas exploration in the northwest continental shelf of Australia,with low degree of oil and gas exploration and lack of geological research data.So far,only a few wells distributed in the Bedout depression in the study area have made commercial oil and gas breakthroughs.In recent years,major oil and gas companies have deployed and drilled Roc-1,Roc-2,Phoenix south-1,Dorado-1,Dorado-2 and Dorado-3 wells in Bedout depression.Among them,Dorado well block obtained industrial condensate oil and gas flow in sandstone of Triassic Keraudren formation,Roc-1,Roc-2 and Phoenix south-1 wells also obtained oil and gas flow.The above exploration and development results fully show that Roebuck basin has the basic petroleum geological conditions for oil and gas migration and accumulation,which is worth further in-depth comprehensive study of oil and gas geology,evaluation and optimization of favorable oil and gas exploration zones,and then guide the next step of oil and gas exploration deployment and drilling decision-making.The strata of Roebuck basin in the northwest continental shelf of Australia are well developed,and the main target strata with large sedimentary thickness are the Triassic,Jurassic and Cretaceous of Mesozoic.The lower Triassic is a set of transgressive system,mainly depositing the shale of locker formation,while the middle upper Triassic is a set of supra coastal system,mainly developing the sandstone of Keraudren formation in the environment of river-shore shallow sea.The Jurassic system is a set of regressive strata,and the delta is widely developed,mainly depositing the sandstone of Depuch formation.Cretaceous is a set of transgressive system,which is mainly composed of delta facies sandstone and fine-grained marine sediments,with carbonate rock at the top dominating.Based on the comprehensive analysis of single well sedimentary facies,connected well with sedimentary facies,seismic profile and well logging data of Roebuck basin in the northwest continental shelf of Australia,the main characteristics of oil and gas distribution are summarized,and the main control factors affecting oil and gas accumulation and distribution are discussed.It is considered that the multiple transgressive regressions in Early Triassic and late Cretaceous controlled the spatial and temporal distribution of the source rocks in the basin.The Jurassic large regressive delta environment not only brought a lot of organic matter,but also provided a reservoir sand body with good physical properties for oil and gas accumulation.At the same time,a large number of tensional complex faults developed in Triassic and Jurassic becoming favorable targets for oil and gas accumulation.At present,it has been found that the sand shale interbedding of the lower Keraudren formation of the middle lower Triassic and the reservoir forming combination of the sandstone reservoir of the depuch formation of the Middle Jurassic and the regional cap rock of the Cretaceous.The source rocks in the keraudren and locker formations of the Triassic in Roebuck basin,Australia,are characterized by high organic matter abundance and maturity.They are dominated by natural gas and condensate oil providing sufficient oil sources.The second stage of the Triassic large delta sedimentary sand body has good reservoir performance and strong sand body connectivity.The Triassic synsedimentary faults control a large number of anticlines,fault blocks and stratigraphic lithologic traps,and in the later stage the Cretaceous regional caprock of Bedout,which is not denuded,has good sealing performance.Based on the above analysis,it is considered that the favorable areas of Pina colada and Dorado are the exploration targets of the lower stage of Roebuck basin. |
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