钻时变化率法及其在渤海油田砂泥岩界面判断中的应用

Method of drilling time change rate and its application to judgement of sand-shale boundary in Bohai Oilfield

渤海油田地层以新生代砂泥岩剖面为主,成岩性相对较差,地层钻速快,钻时变化不明显,而且在定向井钻井过程中受造斜影响,钻时无法直接反映地层岩性的变化,严重影响地质录井作业质量,因而在前人研究的基础上,提出钻时变化率法。钻时变化率包含相对变化率和绝对变化率,通过两者数值的变化,结合岩屑录井,可用于判断砂泥岩地层岩性界面。该方法在渤海油田垦利X构造10口井的应用表明,剖面符合率提高了近10%,较好地解决了浅部地层及定向井造斜井段钻时录井难的问题。

The strata of Bohai Oilfield are dominated by the Cenozoic sand-shale profile,and their diagenesis is relatively poor.Formation drilling rate is rapid,the change of drilling time is not obvious.Moreover,during the process of directional well drilling,drilling time can not directly reflect the change of formation lithology because of the influence of deflecting,which seriously affects the quality of geological logging operation.Therefore,on the basis of previous studies,the method of drilling time change rate was proposed.The rate of change in drilling time includes relative rate of change and absolute rate of change.Combined with cuttings logging,the variation of both values can be used to judge the lithologic interface of sandstone and mudstone strata.The application of this method in 10 wells of Kenli X structure in Bohai Oilfield shows that the profile coincidence rate has increased by nearly 10%.The problem of drilling time with mud logging in shallow formation and deflecting section of directional well was well solved.