THE DYNAMICS AND DEPOSITIONAL SYSTEM AS RESERVOIR ANALOGUE CASE STUDY OF OPAK ESTUARY, SOUTH COAST OF YOGYAKARTA

• Main Authors: Slamet, Sugiarto, Rahmad, Jumadil, Ida Bagus Oka, Agastya, Rheonaldy Septia, Pratama, Nenden Lestari, Sidik
• Format: Article PeerReviewed
• Language: English
• Published: Departmen Teknik Geologi 2015
• Subjects: Geology
• Online Access: https://repository.ugm.ac.id/135415/1/GEO4%20THE%20DYNAMICS%20AND%20DEPOSITIONAL%20SYSTEM%20AS%20RESERVOIR%20ANALOGUE%20CASE%20STUDY%20OF%20OPAK%20ESTUARY%2C%20SOUTH%20COAST%20OF%20YOGYAKARTA.pdf; https://repository.ugm.ac.id/135415/
• Institution: Universitas Gadjah Mada

Research on sedimentology of Opak estuary has been conducted using shallow coring and grab sampling around the estuary of Opak River at the coastal area of Depok Beach, Special Province of Yogyakarta. The result indicates the wave had dominated the process of depositional system on Depok Beach. Shallow coring is done at 8 point of lagoon, point bar, estuary and foreshore. Based on the core data, lagoon facies show the domination of dark mud with high organic contained. Finning upward pattern and sharp contact of pebbly sands material indicates there was a changed in the depositional environment. The lagoon facies at present could be interpretted as an active channel that connected with the fluvial system at past. Estuary Facies is generally dominated by brownish sands but further to the west area mud contained is highly increasing, the fluvial control ran down and environment became deeper are consider as causal factor of the issue. It clearly show on the result of shallow coring that showing of the grains and mud, it indicates that the suspension here was developped better than on the east side near the fluvial and the inlet. Prograding of sands at washover barrier is dominated by thick and wide geometry of planar cross bedding sands. At Foreshore area the main control is marine process with the domination of wave from Indian Ocean that produce clean sands with sedimentary structure of planar cross bedding. SE-NW orientation of the wave had made the Opak River deflected to the west and create a barrier by the sedimentation result of the river its self. Comprehension on modern depositional environment could help as a guide for subsurface interpretation of hydrocarbon exploration. The result of the research on modern estuary environment show Opak Estuary produces the good quality of sands material with its wide and thick geometry with some characteristics of sedimentary structures. Washover barrier and foreshore are two both facies that potential to be the best reservoir at environment system which dominated by wave. The pattern and distribution of the sands is control by the energy of the particular depositional environment.