[ABSTRAK
Formasi Toolachee memiliki penyebaran yang sangat luas di Cekungan Cooper.Padahal ketebalan Formasi Toolachee tidaklah begitu tebal dengan rata-rataketebalan berkisar hingga 300 m. Proses sedimentasi Fm. Toolachee secararegional berupa fluvial (meandering) dengan urutan batuan berupa batupasir,batulempung, batulanau, dan batubara. Batupasir Fm. Toolachee memilikiporositas yang sedang hingga bagus, sehingga dapat bertindak sebagai reservoiryang terbukti mengalirkan gas pada Sumur Meranji-1. Dengan asumsi bahwapenyebaran Fm. Toolachee luas dan terendapkan di semua daerah penelitian,seharusnya ditemukan juga kandungan hidrokarbon pada dua sumur lainnya, yaituCooba-1 dan Pelican-5. Kenyataannya, Cooba-1 dan Pelican-5 tidak ditemukankehadiran hidrokarbon, sekalipun Fm. Toolachee masih terbentuk disana.Hipotesis yang diangkat adalah bahwa ada kontrol stratigrafi yang berpengaruhterhadap akumulasi hidrokarbon pada Fm. Toolachee. Dari hasil analisis sumurdan seismik yang dibantu dengan atribut seismik dan inversi seismik ditemukanadanya perubahan fasies pada zona reservoir di Meranji-1. Zona reservoir terlihattidak memiliki kemenerusan antara Meranji-1, Cooba-1 dan Pelican-5. Penelitianini menghasilkan penyebaran fasies secara lateral dan vertikal pada Fm.Toolachee. Oleh karena itu, sumur-sumur selanjutnya diharapkan mengikuti polapenyebaran fluvial dari batupasir zona target.

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ABSTRACT
Toolachee Fm has widespread deposition which is formed widely in CooperBasin. Although, Toolachee Fm is thin bed formation with thickness averaging300-400m only. Sedimentation process in Toolachee Fm is controlled by fluvialsystem which is formed in meandering depositional environment with lithologyconsists of sandstone, shale, siltstone, and coal. Sandstone of Toolachee Fm hasmoderate to good porosity, therefor it can act as reservoir which is proven byflowing gas in Meranji-1 well. Based on assumption of widespread depositional ofToolachee Fm, hydrocarbon accumulation shall be found in two wells, Cooba-1and Pelican-5. In fact, Cooba-1 and Pelican-5 do not encounter significanthydrocarbon in Toolachee Fm. Hypotehsis were made that stratigraphy has animportant influence of hydrocarbon accumulation in Toolachee Fm. Study result,from integrated study well and seismic interpretation which is supported byseismic stratigraphy, attribute seismic and seismic inversion, show facies changein Toolachee resulting truncated sand body. This study produces a comprehensivefacies distribution both laterally and vertically. Therefor, next well should bedrilled along channel geometry, Toolachee Fm has widespread deposition which is formed widely in CooperBasin. Although, Toolachee Fm is thin bed formation with thickness averaging300-400m only. Sedimentation process in Toolachee Fm is controlled by fluvialsystem which is formed in meandering depositional environment with lithologyconsists of sandstone, shale, siltstone, and coal. Sandstone of Toolachee Fm hasmoderate to good porosity, therefor it can act as reservoir which is proven byflowing gas in Meranji-1 well. Based on assumption of widespread depositional ofToolachee Fm, hydrocarbon accumulation shall be found in two wells, Cooba-1and Pelican-5. In fact, Cooba-1 and Pelican-5 do not encounter significanthydrocarbon in Toolachee Fm. Hypotehsis were made that stratigraphy has animportant influence of hydrocarbon accumulation in Toolachee Fm. Study result,from integrated study well and seismic interpretation which is supported byseismic stratigraphy, attribute seismic and seismic inversion, show facies changein Toolachee resulting truncated sand body. This study produces a comprehensivefacies distribution both laterally and vertically. Therefor, next well should bedrilled along channel geometry]