塔里木盆地乌什凹陷东部下白垩统沉积相及储层特征研究

塔里木盆地乌什凹陷下白垩统主要发育于凹陷东部,以红褐色砂砾沉积为主,粒度粗,分选磨圆均差,为扇三角洲及湖泊沉积体系。扇三角洲平原的泥石流沉积和扇三角洲前缘水下分流河道十分发育,其中扇三角洲前缘砂体是主要的有利油气储集体。该时期的湖泊宽广而浅,其滨浅湖砂坝以薄层状夹于滨浅湖泥岩中,亦为有利的油气储集微相。储层主要为中细粒岩屑砂岩,位于舒善河组中段,属于低孔低渗储层,主要储集空间是粒间溶孔及粒内溶孔。通过对有效储层控制因素的分析后认为,沉积作用以及填隙物含量对储层储集性能影响很大,而成岩作用尤其是溶蚀作用则是改善储层物性的重要因素。结合波阻抗反演预测了三维工区内有利砂体分布,对储层分布预测有重要指导意义。

Research on sedimentary facies and reservoir characteristics of Lower Cretaceous in Eastern Wushi Sag, Tarim Basin

The Lower Cretaceous mainly develops in eastern Wushi Sag of the Tarim Basin, which is a series of redish brown sandy conglomerate deposit, featuring coarse grain size and poor roundness and poor sorting. Fan delta and lake facies are the dominant types of sedimentary facies of Lower Cretaceous in eastern Wushi Sag. Debris flow deposits are common in fan delta plain subfacies, and submerged distributary channels largely develop in fan delta front. The lake was extensive and shallow, and grew shore-shallow lacustrine muddy banks and sand bars, the later interlayered in the former as thin layers. Fan delta front sand body and shore-shallow sand bar are favorable hydrocarbon accumulating bodies. The reservoir is middle-fine lithic sandstone and features low porosity and low permeability, developing in middle Shushanhe Formation. Dissolved pores between grains and dissolved pores in grains are the main storage and accumulation space. The controlling factors of effective reservoir were analysized: sedimentary process and interstitial material are important, and diagenesis especially corrosion is also decisive. The distribution of favorable sand bodies in 3-D seismic work area was predicted by the research on wave impedance inversion, which would direct the reservoir distribution forecast.