长庆油田上古生界河流相砂体叠置模式研究及其在提高水平井储层钻遇率中的应用

Study on superimposed patterns of upper Paleozoic fluvial sand bodies and its application in improving reservoir drilling rate of horizontal wells in Changqing Oilfield

为精确分析长庆油田上古生界河流相储层单期河道砂体与隔夹层在空间上的配置关系进而提高砂体水平井储层钻遇率,将研究区域内煤层、灰岩及高成熟的古土壤层等标志层作为划分沉积单元的等时面,采用等时相控技术进行对比,并应用切片对比法和等高程对比法划分沉积单元。研究表明,长庆油田上古生界河流相砂体由两期或多期单期河道砂体叠加而成,河道内部隔层自然伽马和电阻率曲线的回返程度与隔层厚度有关,厚度越大曲线回返程度越大,曲线回返程度划分为阶梯式、半幅式及基线式,进一步总结出单期河道砂体在侧向上、垂向上的叠置模式:侧向接触关系主要分为砂体孤立型、砂体对接接触型及砂体切叠接触型;垂向接触关系主要分为砂体间歇式叠加、砂体完整式叠加、砂体侵蚀削截式叠加。通过研究单期河道砂体叠置模式,深入分析单期河道砂体与隔夹层在空间上的配置关系,指导水平井轨迹控制,从而提高有效储层钻遇率。

To accurately analyze the spatial configuration of single channel sand bodies,barriers and interbeds in upper Paleozoic fluvial reservoirs in Changqing Oilfield,and then improve the reservoir drilling rate of sand body horizontal wells,marker beds such as coal seam,limestone and high mature paleosoil layer in the study area were used as isochronous surfaces to divide sedimentation units.Isochronous facies-controlled technology was used for comparison,and slice correlation method and isobath correlation method were used to divide sedimentation units.The study shows that the upper Paleozoic fluvial sand bodies in Changqing Oilfield are formed by the superposition of two or multiple stages of single channel sand bodies.The degree of return of the natural gamma and resistivity curves of the barriers in the river channel is related to the thickness of the barriers.The larger the thickness,the greater degree of curve return.The degree of curve return can be divided into the types of stepped,half amplitude and base line.Furthermore,the superimposed patterns of single channel sand bodies in both lateral and vertical directions were summarized.The lateral contact relationships were mainly divided into sand body isolated type,sand body butt-joint contact type and sand body cutting and stacked contact type.The vertical contact relationships were mainly divided into sand body intermittent stacking,sand body complete stacking and sand body erosion truncated stacking.By studying the superimposed patterns of single channel sand bodies,in-depth analysis of the spatial configuration of single channel sand bodies,barriers and interbeds can guide the trajectory control of horizontal wells and improve effective reservoir drilling rate.