摘要:
陆相湖盆烃类储层以碎屑岩占绝对优势。湖盆规模及湖泊水体能量较小,导致碎屑岩储层比海相砂体有更严重的层间、平面、层内和微观非均质性。湖盆碎屑岩充填可归纳为八种模式,决定于构造位置、湖盆演化阶段和湖水面升降。在远源距和缓坡降背景下,沿长轴发育纵向冲积扇—辫状河—曲流河—三角洲充填模式;横向短轴深断裂一侧,在短源距和陡坡降背景下,发育横向冲积扇—扇三角洲—湖底扇充填模式。以这两种模式为端点类型,之间存在一系列过渡类型。此外还有一些特殊的模式:湖盆萎缩期几乎满盆为河流砂体;盐湖蒸发期滨岸地区以砂坪沉积为主。不同沉积环境的碎屑岩储层有各自的非均质性。冲积扇砾岩和含砾砂岩由于其以模态的粒度结构而具有复杂的孔隙结构,筛积物和泥石流沉积的出现加剧了储层的非均质性。河流砂体储层因其粒度向上变细和窄宽度,注水开发石油效果较差,但其产能一般都高。三角洲砂体具有与河流砂体相反的储层非均质性,注水效果好。滩坝砂体体积上很不重要,但以其高产和均质储层引起人们注意。湖底扇重力流砂体作为烃类储层主要位于扇中和断槽控制的水道式砂体和前缘透镜状砂体。通过露头调整丰富定量化的地质知识库以建立陆相储层地质模型,将是储层沉积学面临的主要任务。
Abstract:
Clastic rocks as hydrocarbon reservoir are prevailed overwhelmingly in the continental lake basins. The smaller scales in basin area and water body of lake lead to more serious heterogeneities of interlayer, areal, inlayer and micropore scales in the continental clastic reservoirs than in the marine analogues. Eight clastic filling models can be distinguished in the lake basins depended on the tectonic setting, the evolutional stage when they deposited and the fluctuation of lake level. Under the background of long distance between the sediment source area and the depocenter and the gently gradient slope, the loniitudianl alluvial fan-braided river-meandering river-delta filling model is developed along the long axis, parallel to the strike of tectonic framework, of a lake basin, while the transversal alluvial fan -fan delta-sublacustrine fan filling model is developed in the steep, deeply faulted side along the short axis due to the short distance between the sediment source area and the depocenter and the steeply gradient slope. These two filling models can be regarded as the end-members in the lake basins, among them there are a series of transitional filling patterns developed. Some particular models can also be observed: the fluvial sandbodies all most cover the overall basin during the dying stage, and the sandflat prevails in the littoral environment during the evaporated stage in a saline lake. The clastic reservoirs deposited in different environments are distinctively characterized by their own heterogeneities. Alluviat fan conglomerates and conglomeratic rocks are characterized by the complicated pore-texiure in terms of its bimodal grain texture, also the occurrence of seive and debris flow deposits can much worsen the reservoir heterogeneity. The fining upwards in grain size and narrow width of the fluvial sandbody reser-voir、 bring about a low recovery efficient in waterflooding, however, often a high productivity can be found. A deltaic sandbody just has an opposite reservoir heterogeneity to the fluvial one, and always a high recovery efficient in waterflooding can be got. The beach and bar sandbodies are no significant volumetrically in a lake basin, however, its high productibity and homogeneous reservoir properties have been noticed interestingly In sublacustrine fan environment, the sandbodies, which could be served as hydrocarbon reservoir are mainly of channelized deposit in the middly fan and fault-bounded trough subenvironments and of lenticular deposit in front area. Through outcrop work to enrich a quantified geological konwledge base for building the geological models of continental reservoirs will be a main target facing to the reservoir sedimentologists
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