A Study on High-resolution Sequence Stratigraphy and Hydrocarbon Enrichment Regularity of Fuyu Oil Layer in the Eastward Area of Daqing Placanticline
|School||Northeast University of Petroleum|
|Course||Mineral prospecting and exploration|
|Keywords||Songliao basin Daqing placanticline and its east high resolution sequence stratigraphy Fuyu oil bed sedimentary facies hydrocarbon formed pattern hydrocarbon distribution pattern|
Daqing oilfield is the most important oil and gas production base in China, however, after a nearly five decades of exploration and development, Daqing Oilfield has entered the later stage of oil and gas exploration and development, currently facing a grave situation of reserve-production imbalances and lack of succeeding resources. However, Fuyu oil bed in Daqing placanticline and its east area has great exploration potential, which is a fine exploration main battlefield of Daqing oilfield that can submit oil reserves recently. Therefore, carrying out research on fine high-resolution sequence stratigraphy and sedimentary facies, as well as summarizing oil and gas accumulation pattern in this area have great guiding function and reference value for further oil and gas exploration and development in this area.Guided by the theory of sedimentology and high resolution sequence stratigraphy , based on the seismic, logging, drill core, laboratory analysis and test data, this paper made a systematical and in-depth research on high resolution sequence stratigraphy of Fuyu oil bed in Daqing placanticline and its east area. Based on the study of sedimentary micro-facies, sandstone distribution restricted by the framework of high resolution sequence stratigraphy, and based on the analysis of reservoir formed factors of Fuyu oil bed in the studied area, in view of multiple geologic features and their matching relationship between spatial and temporal, the master control factors in reservoir forming stage were confirmed, the mode of hydrocarbon accumulation of Fuyu oil bed were established and the hydrocarbon enrichment pattern of Fuyu oil bed were summarized, and then the favorable oil and gas accumulation zones in the studied area are predicted. Innovation and acquaintance acquired from above study were as follows.(1) According to the theory and technology of high resolution sequence stratigraphy, a high resolution sequence stratigraphy framework using short-term datum level as a basic unit was first constructed in Fuyu oil bed in the studied area, and the distribution mode of short, mid-term and short-term datum level were summarized. Fuyu oil bed in studied area were divided into two long-term datum levels, six mid-term datum levels and twenty six short-term datum levels. Based on the structural analysis of short-term datum levels, combined the special multi-source accumulation shallow lake-delta sedimentary environment during the deposition period of Fuyu oil bed in the studied area, the structure changes and comparison relationship mode of short-term datum level in different sedimentary phases of Fuyu oil bed were summarized.(2) According to the study of heavy mineral compose and ZTR index character, combined with the rock texture and sandstone distribution character, analysed the orientation and system of source, confirmed the master control range of each source systerm in different periods of the 3th and 4th of Quantou segment.Accounted that the studied area during the deposition of the Fuyu oil bed was mainly controlled by six source system, the north and south source are major and the influence area of every source at different periods were different.(3) Based on the observation and description of core and a great quantity of logging data, the rock phase and electrofacies were systematically analysised, the rock-electricity response mode which reflects the different sedimentation effect and sedimentary environment was established.(4) Based on rock phase, electrofacies and rock-electricity response mode, the types and the character of sedimentary micro-facies were in-depth studied, accounted that the Fuyu oil layer in the studied area was characterized by the unique shallow lake-delta system, which mainly developed shallow lake-delta and shallow lake. Summarized the shallow lake-delta system depositional model of FuYu oil bed in the studied area combined with the research on the plane sedimentary micro-facies distribution of semi-cycle of mid-term datum level, and the distribution characteristic of reservoir sandstones is analyzed under the control of high resolution sequence stratigraphic framework.(5) According to the principle of chemical kinetics, amount and period of hydrocarbon generation and expulsion were studied to the 1th section of Qingshankou hydrocarbon formation in the studied area, the result showed that the hydrocarbon generation period of the 1th section of Qingshankou hydrocarbon formation was begun at the last stage of Nenjiang formation to the beginning of Sifangtai formation in Upper Crataceous, hydrocarbon generation reached to the top at the last stage of Mingshui formation. Hydrocarbon generation amount of the 1th section of Qingshankou hydrocarbon formation was mainly in middle-east area of Sanzhao depression, Chaoyanggou terrace and Wangfu sag which is outside the studied area. Hydrocarbon generation centre was essentially distributed in the middle area of Sanzhao depression, but Chaoyanggou terrace also had the hydrocarbon generation capacity, which is different from the predecessors’awareness of the studies on this region.(6) The oil-source correlation of Fuyu oil bed shows that the source rocks of the 1th section of Qingshankou in Chaoyanggou region are mature source rocks, and there are two oil-sources of Fuyu oil bed in Chaoyanggou region: the source rocks of the 1th section of Qingshankou in Sanzhao depression and the source rocks in Chaoyanggou region. The contribution of the two oil-sources to Fuyu oil bed may be same, which is consisted with the conclusion of the study on hydrocarbon generation and expulsion history, and can confirm that the source rocks of the 1th section of Qingshankou in Chaoyanggou region has the oil generation and expulsion capability, as well as the accuracy of the study on hydrocarbon generation and expulsion history.(7) Based on the analysis of reservoir forming geologic conditions of Fuyu oil bed, the process of hydrocarbon forming was divided into four stages: hydrocarbon generation and expulsion, downward migration, parallel migration, and hydrocarbon accumulation. From the perspective of multi-factors geologic conditions and their matching relationship between spatial and temporal, confirmed the master control features of each estate in the hydrocarbon formed process. The result showed that the bound, distance and layer of hydrocarbon migrated downward were controlled by effective expulsion range of K1qn1 source rock, overpressure and T2 fault assemblage. The direction, pathway and distance of oil parallel migrated were controlled by palaeostructure and the relationship between T2 fault and reservoir. The oil and gas distribution in vertical and planar were controlled by cycle of base level, sedimentary microfacies and current tectonic.(8) Combine with the results of the research on master control factors of every estate in the process of hydrocarbon accumulation, structural history, oil sources conditions and sedimentary micro-facies of research area, the hydrocarbon formed pattern was summarized to four types, they were, Inside source-upper source rock-lower reservoir model, Near source-short distance lateral migration-fault screened in slope zone model, Outside source-long distance lateral migration-inherited tectonic uplift zone model and Multi-source-Multi-lateral migration model.(9) After summing up all the research results, there categories and six sub-categories reservoir forming zones are divided out in Fuyu oil bed, two favorable target areas and four favorable target traps are optimized.