吐哈盆地胜北凹陷三间房组致密砂岩气藏沉积特征及有利区优选

Sedimentary characteristics and favourable area selection of tight sand-stone gas reservoirs in the Sanjianfang Formation of the Shengbei Depres-sion,Tuha Basin

胜北凹陷是吐哈盆地最大的富油气洼陷,随着对中侏罗统三间房组致密砂岩气勘探开发的需求强烈,亟需对三间房组沉积特征进行研究,预测有利勘探区带。通过岩心观察、测井和地震资料分析等手段,结合高分辨率层序地层学对胜北凹陷中侏罗统三间房组致密砂岩气藏沉积特征进行研究,建立三角洲-湖泊沉积体系,预测了致密气藏有利勘探区带。吐哈盆地胜北凹陷三间房组发育3个长期层序(L1,L2,L3)和5个中期层序(M1,M2,M3,M4,M5),中期旋回区域对比良好。M1~M3层序沉积期,主要发育辫状河三角洲-湖泊沉积体系;M4~M5层序沉积期为曲流河三角洲-湖泊。胜北凹陷三间房组有利储层的砂体主要发育于三角洲前缘亚相。平面上M2层序沉积期胜北5井和胜深3井井区、M3层序沉积期胜北5井和胜北6井井区及东北部和M5层序沉积期胜北5井、胜北6井和胜探1井井区为有利勘探区,M4层序沉积期有利储层整体不发育。该研究成果对促进吐哈盆地胜北凹陷三间房组致密气藏勘探具有指导意义。

[Objective]The Shengbei Depression is the largest petroliferous depression of the Tuha Basin.With the strong demand for the exploration and development of tight sandstone gas in the Middle Jurassic Sanjianfang Formation,it is urgent to study the sedimentary characteristics and predict favourable exploration zones of the Sanjianfang Formation.[Methods]Using core,well logging,and seismic data,the high-resolution sequences and sedimentary characteristics of the tight sandstone gas reservoir in the Sanjianfang Formation of the Shengbei Depression were studied.A lacustrine delta system was identified,and favourable exploration zones of tight gas reservoirs were predicted.[Results]Three long-term sequences(L1,L2,L3)and five medium-term sequences(M1,M2,M3,M4,M5)were developed in the Sanjianfang Formation in the Shengbei Depression;particularly,these mediumterm sequences can be regionally identified.The deposition of the M1 to M3 sequences involved a braided river delta in the lake,but the deposition of the M4-M5 sequences involved a meandering river delta in the lake.The favourable tight gas reservoirs of the Sanjianfang Formation in the Shengbei Depression were mainly developed in subfacies of the delta front.On the plane,the Shengbei 5 and Shengshen 3 well areas of the M2 sequence,the Shengbei 5 and Shengbei 6 well areas of the M3 sequence,and the Shengbei 5,Shengbei 6,and Shengtan 1 well areas of the M5 sequence are favorable exploration areas.The favorable reservoir rarely appears in the M4 sequence.[Conclusion]This research can promote the exploration of tight gas reservoirs in the Sanjianfang Formation of the Shengbei Depression in the Tuha Basin.