东营凹陷永安镇三角洲层序地层及其控砂模式

Sequence stratigraphy and modeling of sandbodies distribution in Yonganzhen delta, Dongying depression

针对东营凹陷民丰洼陷及其周缘地区发育的永安镇三角洲沉积,依据地震层序划分原理,结合测井和录井等资料,建立了永安镇三角洲层序地层格架,研究三角洲前缘砂体的展布规律,并对层序控砂模式进行了探讨。将永安镇三角洲目的层位沙三段中、下亚段各划分为一个三级层序,其中沙三段中亚段内部划分出3个四级层序(MSC1—MSC3)、8个五级层序(Z1—Z8),沙三段下亚段内部划分出2个四级层序(MSC4—MSC5)、2个五级层序(X1—X2)。在MSC5—MSC3层序发育时期,永安镇三角洲沉积规模较小;在MSC2层序发育时期,永安镇三角洲物源大量供给、强烈进积,并可推进到胜坨断层下降盘;在MSC1层序发育时期,永安镇三角洲物源持续供给,强度较大,但受到东营三角洲影响,逐渐向北发生迁移。对永安镇三角洲平面和剖面沉积体系演化规律的研究表明,各级旋回内部沉积趋势发生迁移,永安镇三角洲具有层序控砂的自相似性特点,三角洲进积砂体主要发育于各级旋回基准面下降半旋回,且下降半旋回含砂率高于上升半旋回。

The Yonganzhen delta is developed in Minfeng sag and its peripheral area are important oil and gas accumulation belts in Dongying depression, Bohaiwan Basin, China. Based on the principles of seismic sequence, combined with logging and drilling, the target strata of Yonganzhen delta, the middle and the lower submember of third member of Shahejie formation(Es3 z-Es3 x) are divided into a third-order sequence separately. In the sedimentary stage of Es3 z, three fourth-order sequences(MSC1-MSC3) and eight fifth-order sequences(Z1-Z8) are developed; in the sedimentary stage of Es3 x, two fourth-order sequences(MSC4-MSC5) and two fifth-order sequences(X1-X2) are developed. Meanwhile, the scales of Yonganzhen deltaic deposition was small in the periods of MSC5-MSC3; in the period of MSC2, the strength of source supply increased from the Qingtuozi salient, the Yonganzhen delta prograded massively, and reached the downthrown block of Shengtuo fault with the depositions of mixed sources; in the period of MSC1, the Yonganzhen delta migrated to the north is affected by the deposition of the Dongying delta. Moreover, the Yonganzhen delta has the characteristic of selfsimilarities for development of sandbody controlled by sequence. The self-similarities illustrate that the delta sandbody is developed within the dropping semi-cycle in each grade of base level cycle, with the sand content higher than that of the rising semi-cycle.