准噶尔盆地腹部地区中部4区块层序地层分析

SEQUENCE STRATIGRAPHY OF BLOCK 4 IN THE HINTERLAND REGION OF JUNGGAR BASIN

中部4区块位于准噶尔盆地腹部的昌吉凹陷,侏罗纪时堆积了浅水辫状三角洲相粗粒砂砾岩与深水湖泊相泥岩沉积,这些沉积在D2井区显示出多个明显的旋回.根据沉积相序变化、准层序叠加样式、测井曲线特征,通过伴生的低水位域底界面的识别及附近的超失、削截特征分析,仔细追踪和查明了10条关键层序界面,划分出9个三级层序,识别出低水位、湖进和高水位体系域.由于处于关键坡折带的下倾方向,每个层序均具有完整的三分结构,年限平均约5Ma,共识别出27个体系域,准层序组62个,准层序148个.单个层序厚度平均209.3m,单个准层序组平均厚30.4m,单个准层序平均厚13.0m.

The Block 4 is located in Changji depression of Junggar basin, where accumulated braided deltas of coarsegrained gravelstones and sandstones, and deep-water lakes of mudstones, where Jurassic depositions in Well D2 displayed clearly more cycles,10 key boundaries of sequences are traced and found out by using of knowledge of the key break slope belts, identifying of basal boundaries of LST accompanied with the key break slope, and analyzing of near lapouts and truncations; nine sequences were divided on the base of sedimentary facies changes, parasequence stacking patterns and well-logging characteristics, with the lowstand systems tracts （LST）, transgressive systems tracts （TST） and highstand systems tracts （HST） distinguished. Each of sequences to the down-inclined direction of the key slope was characterized by the perfect three-unit structure, including LST, TST and HST; averaged about 5 million age. 27 systems tracts, 62 parasequence sets and 148 parasequences were identified, with the single sequence averagely 209.3m thick, the single parasequence sets averagely 30.4m thick and the single parasequence averagely 13.0m thick.