INTERPRETASI GEOLOGI CEKUNGAN BERAU - PAPUA DAN SEKITARNYA, BERDASARKAN ANALISIS DATA GAYABERAT

Imam Setiadi, Tumpal Bernhard Nainggolan, Ali Albab

Abstract


Cekungan Berau merupakan cekungan yang mempunyai potensi menghasilkan hidrokarbon seperti halnya cekungan Bintuni dan Salawati. Penelitian yang telah dilakukan pada cekungan ini umumnya membahas studi tektonik dan stratigrafi regional serta geokimia. Analisis mengenai pola sub-cekungan dan konfigurasi batuan dasar belum pernah dilakukan pada daerah ini. Pada eksplorasi hidrokarbon, informasi mengenai tebal sedimen pola struktur dan pola tinggian diperlukan sebagai informasi awal dalam memetakan keberadaan deposenter yang ditindaklanjuti dengan survei lebih detail menggunakan metode seismik sehingga penelitian ini penting dilakukan. Penelitian ini dilakukan untuk mengestimasi keberadaan sub-cekungan sedimen, mengidentifikasi pola struktur geologi, dan konfigurasi batuan dasar pada cekungan Berau berdasarkan analisis data gayaberat. Metode yang dilakukan yaitu dengan menganalisis data gayaberat menggunakan analisis spektral, filter polinomial, dan pemodelan 2D. Hasil analisis spektral menunjukkan bahwa ketebalan batuan sedimen rata-rata diperkirakan 3.38 Km, orde yang dipilih dari hasil filter polinomial yaitu orde 6 yang digunakan untuk menentukan anomali regional dan residual. Sub-cekungan yang didelineasai berdasarkan hasil anomali residual gayaberat yaitu sebanyak 6 sub-cekungan sedimen, sedangkan pola struktur yang teridentifikasi yaitu berupa pola tinggian, graben, dan patahan/sesar. Hasil pemodelan 2D menunjukkan bahwa batuan dasar pada cekungan Berau yaitu batuan metamorfik dengan nilai rapat massa sebesar 2.8 gr/cc, lapisan di atasnya di interpretasikan sebagai batuan sedimen berumur PraTersier dengan nilai rapat massa 2.5 gr/cc, di atas batuan PraTersier di interpretasikan sebagai batuan sedimen berumur Paleogen dengan nilai densitas sebesar 2.3 gr/cc, lapisan yang paling atas diinterpretasikan sebagai batuan sedimen berumur Neogen dengan nilai rapat massa sebesar 2.4 gr/cc. Berdasarkan hasil analisis gayaberat menunjukkan bahwa Cekungan Berau mempunyai lapisan batuan sedimen yang cukup tebal dan beberapa struktur tinggian yang diduga sebagai tempat migrasi hidrokarbon yang menarik untuk diteliti lebih lanjut untuk mengetahui keberadaan hidrokarbon.

Kata Kunci : Gayaberat, Analisis Spektral, Polinomial, Pemodelan 2D, Cekungan Berau, Papua Barat


Berau Basin is one of basin that potential to produce hydrocarbons like Bintuni and Salawati Basin. Research that has been carried out in these basins is generally tectonic and stratigraphic regional and geochemical studies. Analysis of sub-basin patterns and basement configurations haven’t been done in these area. In hydrocarbon exploration, information about sediment thickness, structure lineament and basement hight patterns is needed as initial information to mapping the depocenter existence which is followed by a more detailed survey such as seismic methods, so that this study is important to do. The research was conducted to delineate sediment sub-basin, to identify geological structure patterns, and basement configuration in the Berau basin based on gravity data analysis. The method used by analyzing gravity data by using spectral analysis, polynomial filtering and 2D forward modeling. The spectral analysis result showed that the average thickness of sedimentary rocks estimated 3.38 Km. The polynomial order chosen from the results of the polynomial filter is order 6 which is used to determine regional and residual anomalies. The sub-basins were delineated based on the results of gravity residual anomalies were 6 sediment sub-basins, while the structural patterns identified are basement height, graben, and fault. The 2D modeling results show that the basement of the basin is metamorphic rock with a mass density value of 2.8 gr/cc, the upper layer of the basement is interpreted as PraTersier sedimentary rock with a mass density value of 2.5 gr/cc, on PraTersier rocks is interpreted as Paleogene sedimentary rocks with a density value of 2.3 gr/cc, the top layer is interpreted as a Neogene sedimentary rock with a mass density value of 2.4 gr/cc. Based on the results of gravity analysis shows that the Berau Basin has a thick layer of sedimentary rocks and some basement height structures that are suspected as places of migration of hydrocarbons which are interesting to be explored further to determine the presence of hydrocarbons.

Keywords : Gravity, Spektral Analysis, Polynomial, 2D Modeling, Berau Basin, West Papua


Keywords


Gayaberat;Analisis Spektral;Polinomial;Pemodelan 2D;Cekungan Berau;Papua Barat

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DOI: http://dx.doi.org/10.32693/jgk.18.2.2020.671