纯西地区沙四段滨浅湖相的滩坝砂岩以岩性和构造岩性油气藏为主，勘探程度相对较低，具有良好的勘探开发前景。 通过进行古地貌恢复、精细构造解释，并结合钻井资料进行总结归纳后，认为平面上，滩坝砂岩发育分布受构造活动形成的古地貌控制。滩砂分布广泛，呈席状展布于古地形平缓的地带；坝砂局部发育，主要分布于微地形发生变化的位置。剖面上，滩坝砂岩受高频层序控制，坝砂主要形成于基准面短期旋回下降期，滩砂主要形成于短期旋回上升期。进而取得的一个重要认识：由于水平面的不断波动、水动力能波及到不同的缓坡带构造位置，因此坝砂砂体发育的的位置与一个构造的具体高低关系不是很大，而与古地形、水动力的变化关系密切，这就为在构造不同高度钻探提供了依据。 由于滩坝砂储层在地震剖面上很难识别、追踪，通过精细构造解释、古地貌恢复技术、正演技术、多属性分析与特征反演技术等多项技术的运用，能够较为准确地预测出有利的储层发育带和油藏发育区，对有效勘探开发纯西外围探区沙四段、提高钻探成功率具有重大意义。 在纯111、纯110井区选择有利部位部署井位，共完钻井位5口，均钻遇到单层较厚的坝砂油层，取得了较好的经济效果。

Most of the reservoir of Beach-barrier Sandstone in chunxi are lithologic and structure-lithologic oil reservoirs.There are good exploration and develping prospects in this area . By resume palaeogeomorphy、study subtle structure, combined with drilling data, It is considered that beach-barrier sandstone’s distributing is controled by palaeogeomorphy which formed by tectonic action in plane. Beach sands distribute abroadly and spread like sheet in gently slope terrian;barrier sands mainly distribute in the area that micro-structure has changed. In section, the deposite of Beach-barrier sandstone is mainly controled by high frequency sequence. Barrier sand is mainly formed in water descend period of short term cycle, and beach sand is mainly formed at ascend period of short term cycle.Then a conclusion is drawed that the distribution of barrier sand is related to the variey of palaeogeomorphy、water move ,and is rare related to the hignness of the structure. The reason is that the water moved frequently, so the wave can affect different area of the gentle slope zones. That provide the proof of drilling in different altitude stucture. Beach-barrier sand reservoir is hard to be identified and described in normal seismic cross-section. Through using the techniques such as subtle structure interpretion、positive evolution、muti-atrribute analysis，it is more easier to find the favorable reservoir belt in exploration area which is important for developing chunxi district of ES4. Finally we have choosed suitable area such as chun111 and chun 111 area to privide well position.It has finished drilling five wells this year and all have a good results that met the thick barrier sands.