非常规水平井地震导向关键参数分析及预测方法

Analysis and prediction method of key parameters for seismic steering of unconventional horizontal wells

水平井地震导向以三维地震资料为基础,综合地质、录井、测井和随钻实时地质评价等多种资料,为钻井工程提供靶体预估、趋势预判及风险预警等信息,即包括入靶导向(目标地层埋深预测)和水平钻进导向(地层倾角、小断层和微幅构造预测等)。然而,由于非常规储层地质特征不同,其水平井地震导向的难点或侧重点也不同。以滇黔川五峰—龙马溪组海相页岩气和松辽盆地泉四段致密油水平井地震导向为例,由于页岩分布广、箱体薄、成层性好,其地层埋深、地层倾角及小断层和微幅构造精细预测是难点,也是导向的关键问题;而致密砂岩相对较厚,其地层埋深、地层倾角、小断层和微幅构造在地震导向中的精度要求相对较低。砂体叠置关系复杂,横向变化快,是导致水平井出层的主要因素。所以,准确预测河道砂是其导向的难点和关键问题。根据储层地质特征分析,建立地质模型,通过钻探实例详细分析不同储层地震导向的关键问题,并基于水平井实时钻探的特点,应用动态地震勘探理论,建立“动态速度”,不断提高深度域地震数据精度,以解决页岩气地震导向关键问题;通过建立“动态属性”,不断提高致密砂体预测精度,解决致密油地震导向关键问题。这些手段有助于提高水平钻探效率和甜点钻遇率。

Based on 3D seismic data,seismic steering of horizontal wells provides target prediction,trend prediction,and risk warning for drilling engineering by integrating data on geology,logging,and real-time geological evaluation while drilling.In other words,it provides both target-entering steering(predicting the buried depth of target formations)and horizontal drilling steering(predicting formation dip angles,small faults,and micro-amplitude structures).Due to the different geologi-cal characteristics of unconventional reservoirs,the difficulties or emphases in seismic steering of horizontal wells are also different.Seismic steering of horizontal wells of marine shale gas in the Wufeng-Longmaxi Formation of the Yunnan-Guizhou-Sichuan region and that of tight oil in the Quan-4 Formation of Songliao Basin were studied as examples.Owing to the wide distribution,thin box,and good stratification of the shales,the difficulties and emphases in seismic steering of the shale wells were accurate predictions of the buried depth of target formations,formation dip angles,small faults,and micro-amplitude structures.In contrast,the tight sandstones were relatively thick and the precision requirements for the buried depth of target formations,formation dip angles,small faults,and micro-amplitude structures in seismic steering of these wells were relatively low.The main reasons for the horizontal wells to be drilled into other formations were the complex superimposed relationships of sand bodies and rapid lateral changes.Therefore,the difficulties and emphases in seismic steering of these wells were accurate predictions of the channel sands.In this paper,a geological model was built through an analysis of reservoir geological characteristics and with drilling examples,the key problems in seismic steering of different reservoirs were analyzed in detail.In view of the characteristics of real-time drilling of horizontal wells,the dynamic seismic exploration theory was applied to establish a"dynamic speed"and ultimately to continuously improve the accuracy of the seismic data in the depth domain and to solve the key problems in seismic steering of shale gas."Dynamic attributes"were also established,which was aimed at continuously improving the prediction accuracy of tight sand bodies and solving the key problems in seismic steering of tight oil.These methods can help improve the efficiency of horizontal drilling and the drilling ratio at sweet spots.