| Tarim Basin is an important energy basement for transporting nature gas from the west to the east. It has plenty of petreoleum resource that is more than 100×108 t, so Tarim Basin is known to geologists as the oil and gas industry's hope. The Triassic is one of the most significant petroliferous strata..A series of oil and gas pool has been found in Triassic strata in Tahe-Lunnan area over the past few years, at well as good evidences of oil and gas have been acquired in the northwest of Awati aera. It is, therefore, showing a huge exploration potential.Although predecessors have researched the sedimentation and sequence stratigraphy in different tectonic units (especially in Tabei area), the basin wide sequence stratigraphy is researched little. However, due to data limitations, the study area and the use of different different theoretical of sequence stratigraphy, different people have quite different ideas on Triassic. Until now, authorized and trans- region sequence stratigraphic program has not been established. At the same time, because of the limited research on sedimentary facies,sedimentary system, filling evolution and sandbody distribution, the deep cognizance of oil accumulation was weak. Above all, the study of favorable exploration area and oil-gas accumulational regularity is restricted.To solve the above problems, the study is under the theoretical guidance of sequence stratigraphy, contemporary sedimentology, petroleum geology and geophysics, and the overall research of the whole basin is emphasized. We analyzed the 354 seismic data, more than 120 logging and drilling core data of Triassic in Tarim Basin. From a macro seismic sequence analysis, depending on the identification of sequence and system tract boundaries, combining the part and whole of the basin, fully using the regional basin-wide seismic interpretation, carrying out the meticulous comparisonby of drilling sequence in the basement of synthetic demarcation, and combining the palaeontologic marker, a unified sequence stratigraphic framework between well and seismic is established in platform area, and a stratigraphic program in different tectonic units is unified. To the further, the sequence stratigraphic characteristics and models of the depression basin in study area is totally summed up. On the basis of isochronal stratigraphic framework, with the outcop observation, core description,and log facies analysis, combing with rock ty -pe,depositional texture, structure characteristics, ect, types of sedimentary facies, development characteristics, and vertieal and horizontal distribution are analyzed. Eventually the research is used to analyse the types,and control factors of potential lithological and stratigraphical traps and to predict favorable exploration area at the key block, so it will improve the accuracy of reservoir prediction and provide foundation for integral deployment of petroleum exploration.The conclusions of this thesis can be summarized as follows:1. Five isochronous sequence boundaries are developed, the bottom-up is T48, T46a2, T46a1, T46h, T46, and four third-order sequences are divided from T-SQ1 to T-SQ4. By the the regional basin-wide seismic interpretation program, the basal boundary is changed from T50 to T48. So the boundary of Ketu'er formation of Triassic and Sajingzi formation of Permian is amended, which is hard to be distinguished by tailored lithologic character and color.2. By the the the regional basin-wide seismic interpretation program, although both Tazhong and Tabei area are used the 3 sub-programs, due to the thick mudstone in basal Triassic.and the similarity of the mudstone. The thick mudstone in basal T-SQ1 sequence in Tazhong area is formed the deposition during the TST to early HST. Whereas T-SQ1 sequence is widespread absent in Tahe area, The thick mudstone belongs to T-SQ2 sequence during the TST to early HST. Overall, the stratigraphic program between Tazhong and Tahe area is misplaced. Prior program was divided by rock formation, which results in the diachronous phenomenon.3. From the identification of sequence boundaries and analysis of typical inside structure, the "Three triple" structure include LST, TST and HST is beyond doubt.Due to the different positions of the basin margin as well as the conditions of very wide and gentle slope in the lake, small changes of lake level can cause the long-distance migration of shoreline, the lake range is rapidly declined during LST, resulting a small range, thin thickness and the lackage of low fan bodies and large-scale foreset reflection configuration. besides, LST is widespread absent in the slope of high position. The ultra-long-distance onlap is widely developed during TST. The typical feature of HST is that a wide range of gentle foreset reflection is well developed. This is quite different from the pattern of shelf- break background, which develops the low fan and a low wedge with high angle "S" type characteristics. The platform area is the uplift backward unit of foreland basin system, its evolution and sequence structure is controlled by extrusion process. The feature that settlement center within a single sequence and multiple sequence is migrated northward is the concrete manifestation. That is, sequence is controlled by the episodic and bending process.4. In the terms of sequence structure and sedimentary inside evolution, with an environment with gentle slope, shallow water and rich deposition, the braided river delta in the Triassic of platform area was deposited extensively in the shore- shallow lake background,which represent the deposition of broad-shallow depression lake basin. The corresponding 4 kinds of favorable reservoir sand is formed:braided channel, underwater distributary channel, channel mouth bar and distal bar. bathyal facies is only developed during the TST and early HST. Braided channel extends to the underwater with a long distance, the typical underwater channel is formed. And in the background of a small lake level change, the more fine-grained sedimentary bodies of channel mouth bar formed pre-stacked plot in delta sequence are not preserved completely by the erosion and cut-off of posterior underwater distributary channel. At last sand bodies of underwater distributary channel is gradually dominated and the important feather is they're the key sandbodies. They show the constantly advanced to the abdomen of basin and mutually overlying complex delta bodies Finally, the third sequence is "retrogradationâ†'progradation" evolutionary of the internal braided river deltaâ†'brink-shallow lakeâ†'braided river delta. And braided river delta is developed widespreadly in the LST, early TST and middle-late HST, the shallow lake and demi-deep lake thick mudstone is developed during late TST and early HST.5. In view of the ideas that Triassic reservoir sandbodies are extremely developed, reservoir performance is better, distribution is large, secondary hydrocarbon reservoir is the main reservoir and favorable traps are lithologic-stratigraphic and complex structural lithologic traps, the key term of reservoir is whether has valid conduction and blankoff- guarded element. Studies suggest that the following three slope positions have a good exploration prospects:south Tabei-Shunbei area, Manxi-Shunxi area and south Awati area. |
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