区域三维空间岩石可钻性预测方法研究与应用

摘要

In the initial stages of exploration ,w hen drilling data is scarce ,it’s particularly important to predict the drillability of the target formation in a proper ,efficient and low-cost manner .In this paper ,com-mon drillability prediction methods using logging ,mud logging and seismic data were evaluated and deter-mined to be inadequate .So ,to meet the need for effective predicability of formation drillability ,a new 3D prediction method was presented ,in which a model considering both rock acoustic and density properties was constructed by combining the micro-bit drillability test and full-band and high-resolution P wave veloc-ity cube which was generated by awell log-constrained seismic inversion technique .Prediction software was developed to create a 3D visualization of the distribution of drillability .Case studies of two wells in one block of the Tuha Basin was presented .The average error of drillability was about 10% ,and drillability grade of a roller bit was 2.8 6.3 while drillability grade of a PDC bit is 2.0 5.0 .The 3D visualization re-sult indicated that an abnormally high drillability area existed in the local formation ,which was in accord-ance with the existence of conglomerate layer shown in drilling record .The overall drillability performance of PDC bits was superior to that of the roller bits .The results showed that the model considering both rock acoustic and density properties could predict rock drillability reasonably and reveal drillability differences for different bits .The method proposed could describe the spatial distribution of rock drillability in an ob-jective manner ,providing references to speeding up drilling .%在已钻井资料较少的情况下，合理、高效、低成本地预测岩石可钻性在地层空间的分布对钻井工作十分重要。分析了单一测井、录井及地震资料预测方法的不足，提出了预测三维空间岩石可钻性的新方法，即利用测井约束地震反演技术对三维地震数据进行反演，生成全频带高分辨率的岩石纵波速度体，通过室内微钻头岩心可钻性试验，建立了考虑岩石声波时差与密度属性的可钻性预测模型，并据此开发了三维岩石可钻性预测软件。在吐哈盆地某区块两口井进行的实例分析表明，可钻性平均误差约10％，研究区块牙轮钻头对应的岩石可钻性级值约2.8～6.3，PDC钻头对应的岩石可钻性级值约2.0～5.0；软件三维显示结果表明，局部地层存在异常高可钻性级值带，与钻井资料显示该地层存在砾岩层结论相符。该区块PDC钻头的三维空间地层岩石可钻性整体优于牙轮钻头对应的可钻性。研究表明：建立的岩石可钻性预测模型同时考虑了岩石声波与密度属性，能合理预测岩石可钻性，反映不同类型钻头的可钻性差异；新方法能较真实地反映出岩石可钻性的三维空间分布情况，可为制定钻井提速方案提供参考。