Shallow Gas Features Based on Interpretation of Bottom Profilling Records at Topang Delta, Meranti Regency, Riau Province

Purnomo Raharjo, Andrian Willyan Djaja, Ediar Usman

Abstract


One of the tasks in conducting a renewable energy research is finding a shallow gas contained commonly in river deltas. The location chosen is in Topang Delta,, Meranti District, Riau Province in 2015. The research was conducted by using sub-bottom profiling (SBP) method. Biogenic gas indications could be observed in the SBP records in the forms of free reflector, acoustic plumes and acoustic blanket. The shallow biogenic gas at research area is trapped in A and B sequences. Sequence A is characterized by plume gas and acoustic blanket, while B-type biogenic gas is showed by free-reflector feature of 10-15 meters depth. Sediment which does not have porocity such as old clay is required environment for anaerobic bacteria as catalyst in the formation of biogenic gas to be evolved. Old clay sediment is potential as a biogenic gas source rock afterwards migrated to a layer of sand as a reservoir rock. Some parts of biogenic gas does not appear to the surface because there have been traped in cap rock in form of young clay sediment.

Keywords: Topang Delta, Biogenic Gas, free reflector, acoustic plumes, acoustic blanket

 

Salah satu tugas dalam melakukan penelitian energi terbarukan adalah pecarian gas dangkal yang biasa terdapat di delta-delta sungai. Lokasi yang terpilih adalah di delta Topang  Kabupaten Kepulauan Meranti, Provinsi Riau pada tahun 2015. Penelitian yang dilakukan salah satunya menggunakan metoda sub bottom profilling (SBP). Indikasi gas biogenik tampak dalam rekaman subbottom profilling berupa reflektor bebas pantul, terobosan gas dan selimut akustik. Keterdapatan gas biogenik dangkal di lokasi penelitian terjebak dalam sekuen sedimen A dan B. Sekuen A dicirikan dengan kenampakan berupa terobosan gas dan selimut akustik, sedangkan biogenik gas tipe-B dicirikan dengan kehadiran reflektor bebas pantul dengan ketebalan 10-15 meter. Sedimen yang tidak memiliki porositas seperti lempung tua merupakan lingkungan yang dimungkinkan untuk bakteri anaerobik sebagai katalisator dalam pembentukan gas biogenik. Endapan lempung tua berpotensi sebagai batuan sumber biogenik gas kemudian bermigrasi ke lapisan sedimen pasir sebagai tempat tersimpannya gas biogenik. Sebagian gas biogenik tidak dapat muncul ke permukaan hingga lapisan atas karena terjebak dalam lapisan sedimen penutup berupa lempung muda.

Kata Kunci : Delta Topang, Gas Biogenik, bebas pantul, terobosan gas, selimut akustik


Keywords


Topang Delta; Biogenic Gas; free reflector; acoustic plumes; acoustic blanket

Full Text:

PDF

References


Bhattacharya, J.P. & Walker, R.G. (1992), Deltas. In: Facies Models: Response to Sea Level Change (Eds Walker, R.G. & James, N.P.). Geological Association of Canada, St Johns, Newfoundland; 157-178.

Elliott, T. 1986, Deltas. In: Sedimentary Environments and Facies (Ed. Reading, H.G.). Blackwell Scientific Publications, Oxford; 113-154.

Emery, K. O., and Hoggan, D., 1958, Gases in marine sediment, AAPG Bulletin 42, 2174-1153.

Galloway, W.E. 1975. Deltas. New York: Houston Geological Society.

Nichols Gary, 2009. Sedimentology and Stratigraphy, A John Wiley & Sons, Ltd., Publication

Modified from Orton, G.J. & Reading, H.G. (1993) Variability of deltaic processes in terms of sediment supply, with particular emphasis on grain size. Sedimentology, 40, 475-512.

Raharjo, P., Wahib, A., Yosi, M. and Astawa, I.N., 2015, Penelitian Indikasi Keterdapatan Gas Biogenik di perairan Pulau Topang, Kabupaten Meranti, Propinsi Riau, Laporan Internal Pusat Penelitian dan Pengembangan Geologi Kelautan, Internal Report, Bandung.

Rice, D.D. 1993. Hydrocarbons From Coal. AAPG Studies in Geology. Vol 38:159-184.

Ringis, 1986, Seismic stratigraphy in very high resolution shallow marine seismic data. Proc. Jt. ASCOPE.CCOP Workshop, I June 1986, Jakarta, Indonesia (1986), pp. 115-126

Schuller, F., 1952 Over powerful from Echograph examination. Hydrographic measurement 5, 220-231.

Taylor, D. I., 1992. Nearshore shallow gas around the UK cost. Continental Self Research 12, 1135-1144.




Abstracted/Indexed by: