Prediction Study On Traps Within The Third Sand Set Of S-1 Member Of Shawan Formation In Chunguang Block, Junggar Basin, China

Chunguang block located in Chepaizi swell of the northwestern margin zone of Junggar Basin. Oil and gas exploration of this area dated from in the 1950s, when the exploration targets mainly focused on Cretaceous, Jurassic, Permian and even deep-seated Carboniferous, while no pay attention to the Shallow Neogene.When the Shengli oilfield drilled in the Chepaizi block of the west of Hongche fracture zone in 2005, the technicist inadvertently found the light oil layer in the Shawan formation of Neogene from the Pai2 well, thereby which unveiled the exploration prelude of light oil of Tertiary. The next exploration results suggest that the shallow Shawan formation of Chepaizi region has good potential for exploration. However, the early exploration mode of "Bright Spot" had become gradually slow after a breakthrough, which has not directed the oil-gas exploration effectively, so we need summarize a set of new or full-scale exploration mode of oil-gas to direct the exploration of oil and gas.This paper mainly used the data of well drilling and logging of this area, through these material made composite recording and drilling stratigraphic classification, based on nearly 1000km² 3-D seismic data , well data and previous research , through well-seismic contrast, line-drawing of seismic and well tie profile sequence stratigraphic classification, established the framework of sequence stratigraphic of Shawan formation; on this basis, through extracting the sandstone and mudstone velocity value, explicited the type of sandstone of S-1 member of Shawan formation, then using waveform analysis and seismic sand body scanning technology so as to develop sand body scanning of target layer, then conbining seismic faces-sedimentary faces confirmed their type of sedimentary system, and then forecast the faeorable reservoir facies belt and distribution range of effective trap. Through above research,we mainly obtained these progress and know as follows:1)Initially formed a set of methods of using waveform analysis and seismic sand body scanning technology to identify sand body in the seismic profile, through this methods, we can got the sand body plane distrition charateristics of sand formation;2)Through stratigraphic classification of single well to chun3,chun5,chun8,and pai8 well and Top laping of shawan formation to three seismic profile of traverse well in the research area, meanwhile, combining the contrast results of well tie profile, after the comprehensive analysis, we have divided the Shawan formation into three Third-grade sequences, each sequences constituted by LST, TST, HST and FSST, meanwhile, established the framework of sequence stratigraphic of Shawan formation, and basic clear the Shawan formation mainly developed delta deposit and lake sedimentary, preliminary implemented the distribution range of favorable facies belt of sand body;3)Making use of the line drawing of seismic-reflection profile, we summarized the framework of sequences stratigraphic mode of N₁s¹, further confirmed the distribution of sand body of in the framework: where mainly constituted by slope fan,basin fan developing in LST and FSST, and the offlap isolated sand body formed in FSST, in addition,which also contain some delta front and river sides sand body close to shoreline area;4)Through extracting sand-mud stone speed data of 16 wells, we compiled the compaction graph of sand-mud stone of S-1 member of Shawan formation, which reveals that the speed of sand stone generally lower than the speed of mud-stone in the S-1 member of Shawan formation, if it was filled by oil-gas, then the speed of it will be more lower this rule, so it belong to class 1 sand body admitted by N.A Anstey, meanwhile, which laid a theoretical foundation to later waveform analysis and seismic sand body scanning;5)Through the seismic sand body scanning technology(based on waveform analysis to identify sand body), we confirmed the distribution range of sand body of S-1 member of Shawan formation, at the same time, we combining the framework of sequences stratigraphic and seismic facies-sedimentary facies, after comprehensive analysis thinks: it mainly developed this kind of sedimentary system constituted by "delta lobes-slope fan-basin fan" in the S-1 member of Shawan formation sedimentary periods, which totally developed four times of sand formation in the section, while the N₁s₁³ is only one of them;6)In the distribution of sand body basic implement situation, combining the conditions of trap evaluation, we have predicted three larger lithologic-stratigraphic trap in the N₁s₁³, its reservoir mainly is sand beach and bar,slope fan and delta front lake withdrew sand, while the fault is the most important oil-gas migration channel. Combined with the drilling situation of chun8 well, we comprehensive analysis thinks: aforementioned three traps have potential to form a certain scale oil pool, therefore,it can be used as the next exploration target.