Research Of Sedimentary Facies Of Baijiantan Formation And Badaowan Formation In The Baikouquan Area

On the basic theory of sequence stratigraphy and sedimentology,the synthetic anlysis on the geologic and geophysical prospecting data of study area,cobining with the former research,the paper researches strata and sedimentary facies of Baijiantan Formation and Badaowan Formation in the Baikouquan area of Karamay Oilfield systematicly and in depth.And analyzes the distribution and evolution of the sedimentary facies of Baijiantan Formation and Badaowan Formation.By dissecting the entirety characteristics of sequence stratagraphic of Baijiantan Formation and Badaowan Formation in Baikouquan area in depth, identifying the sequence boundaries meticulously, we have identified one sequence boundary Ⅱ,two sequence boundary Ⅲ during the study layer of Baijiantan Formation and Badaowan Formation via unity marker bed on the base of divided the sequence stratigraphic framework of the study area;we have divided three sequence Ⅲ,seven systems tract.Between Lower Jurassic and Upper Triassic of the study area is a parallel unconformity surface,belonging to sequence boundary Ⅱ,and it is also a sequence boundary Ⅲ.we can also identify one sequence boundary Ⅲ between the two sand sets of the third section of Badaowan Formation,so we together identify two sequence boundary Ⅲ and divide three sequence Ⅲ in the study layer.In which,sequence Ⅰ includes Lowstand systems tract,transgressive systems tract and Highstand systems tract, sequence Ⅱ also includes Lowstand systems tract,transgressive systems tract and Highstand systems tract, sequence Ⅲ includes Lowstand systems tract of the upper of Badaowan Formation and transgressive systems tract of the lower of Sangonghe Formation and Highstand systems tract.We have selected Series of contrast marker bed on the base of carefully studing of the characteristics of logging response,in the course of contrasting we must grasp the main line of marker bed firmly,contrasted step by step by the controlling of different levels marker bed.There are three marker bed Ⅰ in study layer:the bottom boundary of T3b,the top boundary of T3b,the top boundary of J1b.There are four marker bed Ⅱ:the boundary between T3b1and T3b2, the boundary between T3b2and T3b3, the boundary between J1b1and J1b2, the boundary between J1b2and J1b3. It develops one marker bed Ⅲ in Badaowan Formation of the study area,it is the boundary between J1b31and J1b32.Through to the9well240.7m core observation of the detailed description, combined with64wells in the comprehensive analysis of the mud logging data, logging data and seismic data, fully digest predecessors in the district of research results, in the use of the theory of classical sedimentation and make full use of modern test and analysis means, to the upper Triassic Baijiantan formation and Lower Jurassic Badaowan Formation in the Baikouquan area features of sedimentary facies were analyzed, and the sedimentary facies have a clear understanding.Based on the classical deposition theory,and to fully digest the previous research in this area, it is thought that in upper Triassic Baijiantan formation in the Baikouquan area is a set of development of fan delta and braided river delta-lake sedimentary system and in Lower Jurassic Badaowan Formation is a set of development of fan delta and braided river delta sedimentary system.We identified3facies,7subfacies and15microfacies in the Baikouquan area in depth studying sedimentary facies mark, and characteristics.The3facies include fan delta, braided river delta and lake facies. The7subfacies include Fan delta plain, fan delta front,braided river delta plain,braided river delta front and braided river prodelta, shallow lake, semi-deep lake—deep lake subfacies. The15micr ofacies include the Fan delta distributary channel, Fan delta flood plain swamp, Fan delta underwater distributary channel, Fan delta channel mouth bar, Fan delta tributary bay, braided river delta distributary channel, braided river delta flood plain swamp, braided river delta underwater distributary channel, braided river delta channel mouth bar, braided river delta tributary bay, braided river delta distal bar, braided river delta prodelta clay, shallow lake mud, shallow lake bar and semi-deep lake—deep lake mud sedimentary microfacies.According to controll15sedimentary facies section graph of the region,show clearly vertical and lateral distribution and variation for sedimentary facies.Through the whole tendcy of8sedimentary facies sections nearly from east to west and7sedimentary facies sections nearly from south to north, and furthermore,based on the analysis of distribution characteristics of sedimentary facies in plane and its evolution of the process,we suggest that during early-middle baijiantan sedimentary period,baikouquan area is the largest lake level rising period of the northwest basin,area climate transform from dampness to semi-humid,water mass of baikouquan area is deeper,develop shallow to half-deep lake parfacies sedimentry; During the second section of Baijiantan Formation sedimentary period,lake level drop,the region of interest transform from shallow and half-deep lake to braided stream delta,develop braided stream delta of the second section of Baijiantan Formation sedimentary period, During the third section of Baijiantan Formation sedimentary period,the lake level go on dropping.it mainly develop fan delta, also braided stream delta.After Baijiantan Formation sedimentary during Late Triassic, northwest of Junggar basin uplift grossly, layer suffer disintegrated.Because of inclined uplifting,it uplifts more severely to northwest. Disintegrate is also more. On the southeast slope, Badaowan Formation sedimentary begins. early days it only deposits at the low of ancient landform, then gradually overlap upward. Badaowan Formation develop mainly fan delta, braided stream delta sedimentary. Owing to damp climate, the fan delta belong humid fan, so don’t develop mud-rock flow sedimentation.During the second section of badaowan Formation sedimentary period,the lake level go on rising, land section decrease, the sedimentary area expand further,go on overlapping; During the second sand bodies of the third section of Badaowan Formation sedimentary period, coarse sediment with priority to glutenite input continuously reduce, deposition input transform to medium sand and fine-sand, mainly develop braided stream delta sedimentary; During the first sand bodies of the third section of Badaowan Formation sedimentary period,the lake level descent a bit, the incision ability of the river into lake heighten, creating stream rejuvenation phenomenon. During the first sand bodies of the third section of Badaowan Formation sedimentary period,mainly develop braided stream delta sedimentation, against the second sand bodies of the third section of Badaowan Formation sedimentary period, the area of delta plain parfacies broaden obviously,and deposition grain continuously thin down,fan delta vanish, the proportion of floodland swamp obviously broaden, region of interest become gradually peneplane.