酒泉石大凹陷第三系储盖组合与勘探潜力分析

RESERVOIR-CAP ASSOCIATION AND EXPLORATION POTENTIAL ANALYSIS OF THE TERTIARY IN SHIDA SAG OF JIUQUAN BASIN

运用以基准面旋回为基础的层序地层学理论和分析方法,综合研究钻井、测井和二、三维地震资料,在酒泉盆地石大凹陷第三系火烧沟组和白杨河组中识别出3个层序界面,将其划分为1个超长期基准面旋回SLSC1和2个长期基准面旋回LSC1和LSC2。研究表明石大凹陷第三系SLSC1发育冲积扇沉积体系、辫状河沉积体系和滨浅湖沉积体系。在等时地层格架约束下,详细分析了其储集层、盖层及储盖组合的发育规律和分布特征与基准面旋回的内在联系,指出本区第三系仍具有较大的勘探潜力,有利储集体分别是位于LSC1基准面上升半旋回的冲积扇扇中和扇缘辫状水道砂以及位于LSC2基准面上升半旋回辫状水道砂,在平面上位于白南5井以北、单7井以南及白南2井以西冲积扇扇中与扇缘过渡区域为构造-岩性复合油气藏和构造背景上的岩性油气藏勘探的有利区域。

By meas of sequence stratigraphy and analysis method based on base level cycle,the data of well drilling,logging,2D and 3D seismic survey are comprehensively analyzed,three boundaries in Huoshaogou Formation and Baiyanghe Formation of Tertiary,Shida Sag,Jiuquan Basin are identified,which are classified as one suppper long-term base level cycle(the 2nd-level sequence) SLSC1 and two long-term base level cycle(the 3nd-level sequence) LSC1 and LSC2.It is pointed out that in Tertiary SLSC1 of Shida Sag,there are well developed alluvial fan sedimentary system,braided river sedimentary system and shallow lacustrine sedimentary system.Constrained by isotime stratigraphic framework,the internal relationship between base level cycle and the development law and distribution feature of reservoir rocks,cap rocks and reservoir-cap association is analyzed in detail,it is also pointed out that there is huge exploration potential in Tertiary in the area,the favorable reservoir area are the ones located in middle alluvial fan and the fan margin braided channels in LSC1 base level semi-rising cycle,as well as in braided channels in LSC2 base level semi-rising cycle,laterally,the structural and lithological association reservoirs in middle alluvial fan and alluvial fan margin in the north of Bainan well 5,south of Dan well 7 and the west of Bainan well 2,as well as the lithological reservoirs developed in the setting of structure are favorable area for hydrocarbon exploration.