准噶尔盆地玛湖凹陷西斜坡三叠系百口泉组扇三角洲优质储集层预测

High-quality reservoirs prediction of fan delta in the Triassic Baikouquan Formation in west slope of Mahu sag,Junggar Basin

针对准噶尔盆地玛湖凹陷西斜坡风南地区三叠系百口泉组扇三角洲砂岩物性空间变化大、优质储集层(孔隙度大于7.4%,渗透率大于0.05×10-3μm2)预测难的问题,在沉积岩石学、地震沉积学以及地震反演和解释理论指导下,综合利用测井、岩心和三维地震等资料开展了高精度层序地层划分、沉积微相描述和优质储集层地震反演研究。建立了风南井区四级层序地层格架,明确了扇三角洲多期水进水退的充填过程,指出SSQ3和SSQ5是优质储集层的发育层系;识别出扇三角洲平原分流河道、河道间和扇三角洲前缘水下分流水道、河口坝、席状砂等沉积微相,指出扇三角洲平原是优质储集层发育相带;通过应用高分辨层序地层纵向边界和沉积相横向边界约束,进行分层相控叠后地震波阻抗反演,提升储集层预测精度,在SSQ3和SSQ5预测5个优质储集层发育区,提出3口井的井位建议,钻探均获工业油流。

High-quality reservoirs prediction of fan delta in the Triassic Baikouquan Formation in west slope of Mahu sag,Junggar Basin.Because of the physical properties of fan delta sandstone of Baikouquan Formation in Fengnan area of west slope of Mahu sag vary greatly in space,it is difficult to predict high-quality reservoirs.In this study,under the guidance of sedimentary petrology,seismic inversion and interpretation theory,high-resolution sequence stratigraphy,sedimentary microfacies description and high-quality reservoir seismic inversion are carried out by comprehensive utilization of well logging,core and 3D seismic data.The fourth-order sequence stratigraphic framework of Fengnan area was established,and the filling process of multi-stage transgression and regression in fan delta was identified.The result indicates that the SSQ3 and SSQ5 are the favorable sequences for high-quality reservoirs development.Sedimentary microfacies including distributary channel and inter-channel bay in fan delta plain,subaqueous distributary channel,mouth bar and sheet sand in fan delta front were identified.It was pointed out that fan delta plain is an optimum reservoir facies belt.The reservoir facies-controlled impedance inversion of separated layers in PSTM was carried out by applying the constraints of vertical boundary of high-resolution sequence stratigraphy and lateral boundary of sedimentary facies to improve reservoir prediction accuracy.Five high-quality reservoir development areas are predicted in the sequence of SSQ3 and SSQ5,and three wells were proposed for drill,which was later proven to have industrial oil flow during drilling.