#TITLE_ALTERNATIVE#

• Main Author: HERI PATRIA KESUMAJANA (NIM 32004002), ASEP
• Format: Dissertations
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/14019
• Institution: Institut Teknologi Bandung

Hydrocarbon generation at the back-arc basin influenced by basin history it self. In general the back-arc basin formed by thinning of the crust caused by rifting mechanism. The thinning of the crust will cause to cut short the distance between the sedimentary basin with the mantle as a heat source and it's will increase the heat in sedimentary basin. The rifting phase usually followed by sag phase.<p>The Tersiery South Sumatra back-arc basin is one of the back-arc basin in western of Indonesia that is categories as a hot basin because of owning the high value of heat flow over the normal back-arc basin in the world. The mean value of heat flow on the world has range of 40-60 mWm-2, while the South Sumatra back-arc basin has the average of heat flow value of 107.95 mWm-2.<p>The South Sumatra back-arc basin is starting by the rifting phase at the Late Oligocene (30-25 Ma) activated the old basement fault forming three pattern that is Jambi pattern with the direction of the basins are N30E-N50E. This pattern are the dominant pattern in South Sumatra back-arc basin, second pattern is Sunda patern with direction N350E-N15E and the last pattern is Sumatra pattern witch has direction N285E-N330E. During rift phase The Lahat Groups are deposited uncoformable to Pre-Tersier basement and volcanic Kikim Formation. The rift phase is followed by sag phase beginning at Middle Miocene, at this moment the Talang akar to Gumai Formation are deposited. Followed by compresion regim to forming Bukitbarisan mountain and rech the maximum at Plio-Pleistocene.Since Middle Miocene to recen the Formation Air benakat trough kasai Formation are deposited wich characterized by volacanic materials.<p>To reconstruct the thermal history on the South Sumatra back-arc basin are costructed by the gravity modeling and thermal modeling to get the present day thickness of the crust. 1D burial history using Airy isostasy, and cross-section restoration are used to get the &#946;-factor and thermal modeling is used to reconstruct the thickness of the crust offer the time. The validation of the temperature history can be done by comparing the vitrinite reflectance model and the vitrinite reflectance data after converting the temperature history to the maturation history using Easy% Ro method. The vitrinite reflectance data in the South Sumatra basins are generally come from kerogen type II, witch can be suppressed caused by the abundance of non-vitrinite maceral. So that before the vitrinite data can be used as a validator it self must be corrected to eliminated the suppression.<p>By using three gravity cross-section with the sediment layers are restricted to seismic interpretation and density are averaging from well data.<p>The thermal model and gravity model are done by three seismic interpretation section with gravity data passing through Graben Jambi Complex, Graben Limau-Tepus Complex and Graben Saung Naga. This three cross-sections are used to modeling the moho depth. Counted 17 drilling well data around the seismic interpretation section are used for hydrocarbon maturity modeling and also counted 39 the well witch has the thermal conductivity and geothermal gradient data are used to modeling the present day moho depth.<p>The termal model and gravity model are indicated the depth of moho at present day at 15.6 km. From gravity models are indicated the intrusion body which is become sill in the Tempino-176 well at Graben Jambi Complex. As a result of thin crust are the high surface heat flow at present day with average value of 88.48 mili W/m2. The result of thermal modeling, 1D subsidence modeling and crosssection restoration revealed the depth of moho is also shallow from the beginning of basin formation. The depth of moho is between 15.6-19.5 km.<p>The result of the thermal modeling is indicating the heat flow increase at 15 to 5 Ma. with average value heat flow equal to 116.56 milli W/m2. The increasing of the heat flow regionally match with forming of Bukit Barisan volcanic activity.<p>Pursuant the result of calibrating thermal history by the vitrinite data is suggested that the heat flows are not constant trough time. The heat flow will increase at the rifting phase, decreasing at sag phase and increase again to the present day. It will implicate to the maturation modeling when used the constant heat flow taken from present day heat flow data will caused the hydrocarbon maturity model is to high comparing to the vitrinite data.<p>The Sumatran pattern has highest maturity level comparing to other pattern, which is reaced the Early Mature Oil Generation at 25.2 Ma and then reached the End of Gas Generation at 16 Ma. The Top Oil Window is reached at depth 1.433 km.