东胜气田什股壕地区下二叠统山1段河道识别

Identifying channels in the Lower Permian Shanxi 1 Member,Shiguhao area,Dongsheng gasfield,Ordos Basin

鄂尔多斯盆地东胜气田什股壕地区下二叠统山西组是一套由辫状河三角洲向辫状河过渡的沉积相,砂体横向变化快,纵向叠置复杂,薄层、薄互层砂体预测较难。已有钻井揭示山西组山1段气藏部分天然气高产井分布与砂体尖灭线关系密切,为了精确预测山1段的河道砂体展布特征,深化对该气藏的认识,以什股壕地区的三维地震资料、钻井资料、测井资料为研究对象,以地震沉积学理论为指导,利用三维地震资料的横向分辨率解释优势,应用90°相位转换、地层切片等技术对山西组进行河道识别。研究结果表明:①90°相位转化技术对薄砂体的识别更加精确,采用90°相位转换后的地震数据体进行地层切片的提取能够更准确地刻画河道空间展布及河道的边界;②已有钻井揭示什股壕地区山1段气藏有利区位于河道砂体上倾尖灭与构造高部位处,气藏类型为地层—构造复合气藏。结论认为,所形成的基于地震沉积学的河道精细识别技术,为指导研究区气藏精细描述及开发奠定了基础。

The Lower Permian Shanxi Formation,Shiguhao area,Dongsheng gasfield,Ordos Basin,is a set of transitional sedimentary facies from braided river delta to braided river.And most sandbodies in this formation are characterized by fast lateral change and complicated vertical superimposition,so it is really hard to predict these sandbodies of thin bed and interbed.Existing drilling data reveal that Shanxi 1 gas reservoirs in some high-yield gas wells are closely related to sandbody pinchout.In order to accurately predict the distribution characteristics of channel sandbodies in the Shanxi 1 Member and deeply make clear the Shanxi 1 gas reservoirs,the channels of Shanxi Formation in Shiguhao area were identi⁃fied according to some 3D seismic,drilling,and well-logging data,by means of two technologies of 90°phase transition and strata slice,3D seismic interpretation advantage in lateral resolution,and theory of seismic sedimentology.Results show that(1)the technology of 90°phase transition is more accurate in identifying thin sandbodies.And when seismicdata volume processed by this technology is used to extract strata slice,both spatial distribution and boundary of channels can be depicted more precisely;and(2)drilling practices exhibit that several favorable zones of the Shanxi 1 gas reservoirs in Shiguhao area are located in the updip pinchout of channel sandbodies and the structural high.These gas reservoirs are of structural-lithologic compound ones.In conclusion,the method developed for fine channel identification based on seis⁃mic sedimentology may provide the foundation for fine description and development of gas reservoirs in this study area.