Academic literature on the topic 'Sequence stratigrapy'

The area of this study include to PT. Energi Mega Persada Tbk work area. The area of this study is located in Jambi Sub - Basin, South Sumatera Basin. This study is emphasized to examine the sequence stratigraphy of Talang Akar Formation. The data that is used in this study include core, mudlog, 3D seismic, well log, and palynomorf fossil. The result of those data analysis and data correlation are lithofacies, electrofacies, depositional environment, and stratigrahys sequences of Talang Akar Formation. From data analysis, the facies’ that develop in Talang Akar Formation are A, B, C, D, E, F, G, H, I, J, K, L, and M. Those facies’are deposited in fluvial – deltaicenvironment at Late Oligocene until Early Miocene. From the well correlation and seismic interpretation, the sediment distribution pattern of Talang Akar Formation become thicker and deeper in the west side and the highland is located relatively in the east of the study area. At the area of study Talang Akar formation is very influenced by structure. From the lithofacies and electrofacies analysis, there are six kinds of stratigraphy sequencesthat develop in the study area. System tracts LST-1 (braided channel) just developed at sequence-1. The other sequences developed TST 1 – 4 (floodplain meandering channel), TST 5 – 6 (marsh delta plain), HST 1 – 4 (crevasse splay meandering channel) and HST 5 – 6 (floodplain delta plain). . Keywordsi: Sequence stratigraphy, facies,depositional environment, Talang Akar Formation, Jambi Sub - Basin. Daerah penelitian termasuk ke dalam wilayah kerja PT. Energi Mega Persada Tbk. Daerah penelitian berada di Sub – Cekungan Jambi, Cekungan Sumatera Selatan. Studi ini difokuskan untuk membahas sikuen stratigrafi Formasi Talang Akar. Dalam penelitian ini, data yang digunakan adalah core, mudlog, seismik 3 dimensi, well log, dan fosil palinomorf. Hasil dari analisis dan korelasi data tersebut adalah litofasies, elektrofasies, sikuen stratigrafi, dan lingkungan pengendapan dari Formasi Talang Akar. Dari analisis data tersebut didapatkan bahwa fasies yang berkembang pada Formasi Talang Akar adalah fasies A, B, C, D, E, F, G, H, I, J, K, L, dan M. Fasies tersebut diendapkan di lingkungan fluvial – deltaic pada umur Oligosen Akhir sampai Miosen Awal. Berdasarkan korelasi antar sumur dan interpretasi seismik, distribusi sedimen Formasi Talang Akar lebih menebal dan mendalam pada sisi barat dengan tinggian yang berada relatif pada bagian timur daerah penelitian. Pada daerah penelitian Formasi Talang Akar sangat dipengaruhi oleh struktur serta berdasarkan analisis litofasies dan elektrofasies terdapat 6 sikuen yang berkembang pada daerah penelitian. System tracts LST-1 (braided channel) hanya berkembang pada sikuen-1. Pada sikuen lainnya berkembang TST 1 – 4 (floodplain meandering channel), TST 5 – 6 (marsh delta plain), HST 1 – 4 (crevasse splay meandering channel) dan HST 5 – 6 (floodplain delta plain). Kata kunci : Sequence stratigraphy, facies, depositional environment, FormasiTalang Akar, Sub Cekungan Jambi.

Sequence stratigraphy revolutionized the field of stratigraphy in the late 1970s and 1980s by providing an interpretive depositional framework for integrating diverse stratigraphic data at the scale of sedimentary basins. However, a lack of consensus on criteria for recognizing, mapping and hence dating sequence boundaries, interpretations of uneven quality, and doubts about the universal eustatic origin and global synchrony of unconformity-related sequences limit the usefulness of sequence stratigraphy in chronostratigraphy.

It is considered that discussion on adaptability of sequence stratigraphy in fluvial sedimentation is significant for oil exploration. As the main controlling factor is the sea-level fluctuations in the coastal river system, Exxon sequence stratigraphy can be applied to divide the sequences into: lowstand, transgressive and highstand systems tracts. And in the inland fluvial system, the application of low- and high-accommodation systems tracts may keep more coincident with the actual stratigraphic record. From the Exxon stratigraphy to low- and high-accommodation systems tracts, each model will be of great value in the petroleum exploration because of the lateral phase transition raised and the vertical phase transition predicted. However, controlled by many allogenic processes, fluvial strata still shows many problems in which the patterns can not be clearly explained. Thus, fluvial sequence stratigraphy needs to be further developed. Researching on various models of fluvial facies sequence stratigraphy in the development process will bring the important theoretical and practical value to the oil reservoir exploration.

Seismic reflection profiles from the Makassar basin have been analysed in terms of seismic stratigraphy. Systematic patterns of reflection terminations indicate the existence of at least three surfaces of discontinuity across the profiles-designated in order of superposition as C1, C2 and C3 - which define the boundaries of four seismic sequences, ie. :- seismic sequence I : topped by C1- seismic sequence II : the interval between C1 and C2- seismic sequence III : the interval between C2 and C3- seismic sequence IV : the interval between Cz and the sea floor Seismic sequence II is dominated by basin slope and basin floor seismic facies whereas seismic sequences II and IV consist of mainly shelf and shelf margin seismic facies. Correlation of seismic sequences with well data facilitates the exposition of basin development, The Late Cretaceous-early Tertiary regional uplift and erosion produced a major unconformity C1, upon which the transgressive facies of seismic sequence II was deposited. A lowstand of sea level due to the so-called intra-Mio- cene orogeny occurred in the upper Early Miocene and produced the C2. Deposition of seismic sequence III is marked by a relative rise of sea level, probably followed by another lowstand of sea level during Mio-Pliocene which formed the C3. The final event is an overall transgression and deposition of seismic sequence IV, with a possible minor lowstand of sea level in Pliocene-Recent, The occurrence of basin slope and basin floor seismic facies within seismic sequence II suggests that in the pre-Lower Miocene, basin subsidence was slightly greater than the rate of depositions. Since Lower Miocene both subsidence and sedimentation rates were equal and the deposition of shelf and shelf margin seismic facies of seismic sequences III and IV was prevailed in the basin.

Based on the theory of sequence stratigraphy, sequence stratigraphy framework of is established in this paper by comprehensively search of core, logging and 3-D seismic data. Zhalainuoer group in Cano Depression is divided into 5 3rd-order sequences: Sq1、Sq2、Sq3、Sq4、Sq5 from down to up. Based on the division and comparison of sequence formation, the sedimentary facies and the depositional system are proposed to study in the paper, and the main depositional systems are detailed explained. The distribution of these depositional systems is controlled by the sequence framework.

Missole facies description and sequence stratigraphy analysis allow a new proposal of depositional environments of the Douala sub-basin eastern part. The sediments of Missole outcrops (N’kapa Formation) correspond to fluvial/tidal channel to shallow shelf deposits with in some place embayment deposits within a warm and semi-arid climate. Integrated sedimentologic, palynologic and mineralogical data document a comprehensive sequence stratigraphy of this part of the Douala sub-basin. Five facies associations occur: (1) facies association I is characterized by Floodplain deposits; (2) facies association II is Fluvial to mouth bar deposits; (3) facies association III characterise Shallow Shelf deposits; (4) facies association IV represents Distal bay or Lacustrine déposits; and (5) Facies association V is made of Fluvial channel deposits. Six depositional sequences were identified. These sequences are composed of four progradational sequences and two retrogradational sequences containing a fluvial channel portion represented by lag deposits at the base of retrogradational sequences. These deposits represent the outset of the relative sea level rise period. In the study area, the N’kapa Formation is composed of non-marine/coastal aggradational deposits representing the early stage of the regressive period. The occurrence of the estuarine/bay deposits with paleosols development is interpreted as evidence of climate change with significant relative base level fluctuation. The study of key minerals associated to sequence stratigraphy as well as palynology demonstrated that sequence architecture has been controlled mostly by climate evolution and outcrops are dated Paleocene – early Eocene.

According to the fundamental principles of high resolution sequence stratigraphy, this paper focused on the application of high resolution sequence stratigraphy to Silurian strata in Tazhong area. Based on the comprehensive study of logging, drilling and seismic information, the high resolution sequence boundaries of Silurian strata and two scales of datum level cycles (long-term and intermediate-term) can be recognized in Tazhong area. Seven chronstratigraphic boundaries can be recognized in Silurian strata, including four sequence boundaries, which were the transformation from datum level falling to datum level rising, and three flooding surfaces, which the transformation from datum level rising to datum level falling. The Silurian strata in Tazhong area can be divided into three third-order sequences which correspond to three long-term datum level cycles, and 11 fourth-order sequences (parasequence sets) relating to 11 intermediate-term datum level cycles. The classification aforementioned can much better solved the corresponding problem between the six lithological sections of Silurian strata and sequence formations, finally establishes the high resolution sequence stratigraphic framework of Silurian strata in Tazhong area.