鄂尔多斯盆地王窑地区上三叠统长6油层成岩作用研究

Diagenesis of Chang-6 Reservoir in Wangyao Area of Ansai Oilfield

通过多项测试方法 ,对安塞油田王窑地区长 6油层含油砂体的岩石学、成岩作用、储集物性和孔隙发育特征进行分析和研究。结果表明 ,该区储集砂体为成分成熟度较低的长石砂岩 ;主要自生矿物为绿泥石、浊沸石、方解石、石英、钾长石、伊利石和钠长石等 ;储层次生孔隙发育 ,主要孔隙类型为粒间孔隙、骨架颗粒溶孔和浊沸石溶孔。孔隙结构具有小孔、细喉的特点 ;储层成岩演化阶段处于晚成岩 A亚期 ;储层性质明显地受到沉积微相和成岩作用的影响。沉积物粒度较粗、厚度较大的河道砂和河口砂坝砂的储集物性明显优于各种粒度较细。

Sedimentation during the stage of Chang 6 deposition was controlled by a lacustrine delta system. The Chang 6 member is an important finger bar reservoir sandstone in the Wangyao area of Ansai oilfield.Chang 6 reservoir in the Wangyao area mainly consists of fine grained sandstone and minor siltstone. The sandstones can be classified as compositionally immature arkoses. The main diagenetic minerals of the sandstones include authigenetic clay minerals, calcite cement, quartz and feldspar overgrowth, albite and laumontite. The authigenic quartz overgrowths and micro crystals contain a variety of organic fluid inclusions that indicate the petroleum filling history. Secondary porosity has been created mainly by feldspar, rock fragment and laumontite dissolution. The dissolution mechanisim is closely related to organic acids and transformation of clay minerals in adjacent source rocks. Based on diagenetic events related to temperature, the reservoir diagenetic stages can be classified into A substage of later diagenesis. The reservoir quality is controlled mostly by sedimentary microfacies and diagenesis. The distribitary channel and mouthbar sandbodies are commonly of high porosity and permeability, whereas the front sandsheets may be of low petrophysical properties.