| Qianjiadian depression is belong to Liaohe basin depression,which is a relatively low level of exploration.lt also belongs to a negative secondary tectonic units in KailuBasin.The overall structure is long and narrow,which studies the work area located in HuliHai Sag. The HuliHai Sag was the lower cretaceous sedimentary thickest and the largest of Qianjiadian depression, north east-north-northeast trending.What is more,It can also be divided into three secodary tectonic units,which are the western fault zone, the central subsag and eastern slope belt respectively.However the western fault zone is the important studying area of this research. The work zone area is about 200 square kilometers,the exploration level is lower,there are totally 16 exploration wells,13 wells distributed in the western depression in order to bring down the 11 wells which are tested in the work area.Unfortunately,only the Qian202 and Qian2 which are located in the western slope can obtain the industial oil flow. From the current level of exploration analysis, there is a large area of the remaining resource potential. Due to the low level of exploration and the limited number of drilling,added the undeveloped stage,we faced a lot of problems such as the limited information and the huge amount of work,because of the low level of sedimentary types,modes and evolution of research in this target layer of Jiufotang and Shahai,it makes impossible for us to deposit the entire work area of the law of systematic and comprehensive research, which has seriously hampered the development of the oil and gas reservoir exploration steps. The study is based on the sedimentology theory, geological, logging, seismic testing, laboratory analysis and other information,taking advantage of different scales and methods of drilling, logging and seismic data,combined with the technologies for deposition system and sedimentary facies, depositional model,in oder to establish the area and complete the study on the work area next to the Cretaceous JiufotangShahai sedimentary evolution process, providing strong support for the prediction of geological research phase under favorable reservoir facies work area.The study firstly compared the work area and seprated the formation, after analyzing the analogy tradition "cycle control, classification contrast" approach, the classic method of sequence stratigraphy and high resolution sequence stratigraphy method, we finally adopted the high-resolution rate of sequence stratigraphy methods which can be studied in the regional stratigraphic studies in recent years.Based on the theoretical basis of the new approach, the main purpose of the work area and the sand layer Jiufotang formation can be divided into strata Jiufotang MSC1, MSC2 two medium-term cycles from bottom to top corresponding to Jiufotang lower and upper section of the formation, the formation is divided into Shahai MSC3, MSC4, MSC5 three mid-cycle, and then base on cycle-based level and other comparison method, by comparing the work area 4 sectional skeleton, we found that the work area is gradually thickening from north to south and from west to east. For further study of sedimentary facies,we make a conclusion based on logging, core, petrographic analysis data these four aspects purpose, lithology changes, rock particle size, composition are also considered. Finally, we concluded that the work area is divided into three main sedimentary facies,they are nearshore subaqueous fan, fan delta, lacustrine, nearshore subaqueous fan which divided fans into three-phase,they are root, fan, the fan sub-end, and there are also 5 mud microfacies which are the main channel, the channel between, braided channel, braided channel between fan-end category; fan delta divided into fan delta front, the former two types of micro-phase fan delta, underwater distributary channel, underwater distributary channel and mouth Shaba class 3 microfacies; shallow lake facies of the lake shore, semi-deep lake-deep lake categories subfacies mud flat, two types of micro-phase Shaba. For regional distribution characteristics of sedimentary facies in accordance with the "Spot-Line-Area" for the idea to start the first "point" that single well phase, there are intervals of coring drilling directly based on the core observation and description of the results of sedimentary facies division, non cored interval combined core and log data which summarized comprehensive logging and seismic facies, analysis of sedimentary facies, after the completion of 11 wells in the work area of object layer of single well facies,we can do a "line "Research. When comparing the previously established strata within the framework contrast, couplet well phase comparison study found that the lower strata in the eastern Jiufotang with gentle slope fan delta sediments, mainly developed nearshore subaqueous fans in the western steep slope belt, Shahai developed an upper strata lake phase and when it moves from east to west,it became faster, more complex, however when it moves from north to south it became a single sedimentary facies types, change more stable. Research on the "face" is carried out on th base of the regional geology in single well phase, cross-sectional analysis, the study found nearshore subaqueous fan is mainly distributed in the western steep slope belt sag, roots fan, more developed at the fan; fan delta located in the eastern sag with gentle slope; lacustrine facies distribution in the central sag, lacustrine phase patchy distribution in sag slope sides, semi-deep lake-deep lake facies to sag in the middle. After completing the study of "dot-line-side", according to the last one "field",which is a sedimentary evolution model,we found that in sedimentary Jiufotang,intense tectonic movement, volcanic eruptions active, intense boundary fault activities under the influence of difference block activities affect the surrounding mountain’s uplift and down, height difference exit, there is water handling clastic between its source material, there are peripheral sag even inside the base of the volcanic eruptions, the formation of tuff, which belongs to a plurality of contiguous overlapping braided channel close and rapid filling of formula deposition, resulting in steep section sag (sag west) bit development nearshore subaqueous fan; small eastern slope which is a gentle slope belt developmental fan delta. Sag subsidence center is located in the eastern, southern sag small area; the northern sag is larger,Qian 30 well is located in the center of sag at the edges. Sag body belongs to semi-deep lake to deep lake.In the Jiufotang advanced deposition, the regional volcanic activity stopped, the rift activity was still strong, particularly in the west,howeverthe east fracture became more intense,causing a sag center shifted westward, gradually the sag range expansion of the water deepened. In contrast, eastern faulting weakened, sedimentary strata more gentle. Detrital material is mainly composed of a number of mountain rivers earring into the lake, forming a mat or ribbon-shaped fan delta sand bodies. In the western slopes of the site, the development of nearshore subaqueous fan deposits. Shahai period sedimentary basin subsidence has entered a stable fracture,from a greatly weakened sharp drop to a slowly lake steady sinking. Depositing the period basically inherited the characteristics Jiufotang lower, however, due to the height difference between the lake and the height difference, sediment supply is lacking,so the performance is belong to the vast semi-deep lake sediments. Shahai sedimentary basin changes to shrink, deltas scale became smaller, the slope of each deposition is composed of mud, sand and mudstone layers.when it comes to a Fuxin group, the lake changs to a further contraction period,the performance of the entire basin belong to the filled deposition.According to the sedimentary characteristics and evolution stemed from the cross-sectional single well sedimentary facies analysis, the well section sedimentary facies analysis and phase plane analysis, combined with regional geological data and logging data to the guidance of the principle of modern sedimentology, we concluded the eventual establishment of sedimentary characteristics and evolution of HuliHai depression inShaHai formation-Jiufotang formation. |
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