榆林气田标志层法和沉积旋回法水平井导向技术

A Geo-Steering Technique Using Marker and Sedimentary Cycles in Horizontal Well Drilling in the Yulin Gas Field

针对鄂尔多斯盆地榆林气田水平井钻进山2~3砂体时存在的入窗困难和入窗后井眼偏离气层段穿行等难题,分析了该气田30多口井的沉积层序和山2~3砂体沉积韵律,发现山2段发育3套距山2~3砂体厚度稳定的煤系地层,山2~3砂体由多个正韵律单砂体在垂向上叠加而成。因此,将煤系地层作为标志层预测山2~3砂体顶界垂深,形成了标志层法水平井入窗导向技术;将山2~3砂体沉积旋回特征与钻时、岩屑、气测值和随钻伽马变化特征结合,形成了沉积旋回法水平段穿行导向技术。该技术在YuH1井和YuH2井进行了应用,砂岩钻遇率分别达到了98.2%和95.6%。标志层法和沉积旋回法水平井导向技术为水平井准确入窗和提高砂岩钻遇率提供了高效的地质导向方法。

In order to solve the difficulty of entering the horizontal well of the Shan2^3sand body of the Yulin Gas Field in the Ordos Basin and the problem of deviation of the wellbore from the gas layer after entering the window,the sedimentary sequence of more than30wells and the sedimentary rhythm of the Shan2^3sand body in the Yulin Gas Field were studied.It is found that there are three sets of coal-bearing strata in the Shan2approximately the same distance to the Shan2^3sand body,and the Shan2^3sand body is superimposed by a plurality of positive cyclothemic vertical single sand bodies.Therefore,the coal-bearing strata were used as the marker to predict the top boundary of the Shan2^3sand body,and the marker based window entering method for horizontal wells was developed.The sedimentary characteristics of the Shan2^3sand body were combined with the variation characteristics of drilling time,cuttings,gas measurement and Gamma ray while drilling to establish the sedimentary cycle based horizontal section geo-steering technique.Through those techniques applied in the Well YuH1and YuH2,sidetracking was eliminated,and the encountering rate of sandstone reached98.2%and95.6%,respectively.The marker layer method and the sedimentary cycle horizontal well guidance technology provide an efficient geosteering method for accurate horizontal window entry and improved sandstone drilling rate