岩屑伽马能谱录井技术推广应用

Promotion and Application of Rock Debris Gamma Spectroscopy Logging Technology

目前油田勘探领域从常规油气向致密油、页岩油气等非常规油气转移,新钻探井型以水平井为主,由于钻井工艺的改进导致井底返出的岩屑较细、较碎,加上油基钻井液对岩屑的影响,给传统岩屑录井和储层解释评价带来较大的困难,增加了水平井准确入靶及保持高钻遇率的难度。为了解决黔北狮溪向斜地区水平井钻进过程中岩性识别、层位划分、辅助地质导向顺利入靶、判断是否顺层钻进以及储层解释评价等难题,在该地区引入岩屑伽马能谱录井技术。通过分析岩屑获得放射性元素铀、钍、钾、伽马以及无铀伽马等岩屑伽马能谱参数,根据页岩油气自生自储及高有机质的特征,借助岩屑伽马能谱参数及衍生参数的变化,辅助解决了岩性识别、层位划分、水平井入靶及提高钻遇率过程中的难题。优选岩屑伽马能谱参数铀、伽马数据拟合出适合黔北狮溪向斜地区总有机碳含量的计算公式,结合气测全烃值的变化建立了页岩气解释模板。实际应用表明该方法实现了储层流体快速解释评价、划分地层、判定沉积环境、辅助入靶、提高储层钻遇率目标。该方法可在类似区块推广应用。

With the shift of oilfield exploration from conventional oil and gas to unconventional oil and gas such as tight oil and shale oil and gas,horizontal wells dominate the new drilling well types now.The improvement of drilling technology has led to thin and fragmented rock cuttings returning from the bottom of the well.In addition,the influence of oil-based drilling fluid on rock cuttings has brought great difficulties to traditional rock cuttings logging and reservoir interpretation and evaluation,increasing the difficulty of accurately targeting horizontal wells and maintaining high drilling encounter rates.In order to solve the problems of lithology identification,stratigraphic division,assisting geological guidance to smoothly enter the target,determining whether to drill along the formation,and reservoir interpretation and evaluation during horizontal well drilling in the Shixi syncline area in northern Guizhou,the gamma ray spectroscopy logging technology of rock debris is introduced.Energy spectrum parameters of radioactive elements such as uranium,thorium,potassium,gamma and non-uranium gamma are obtained by analyzing rock debris.According to the characteristics of shale oil and gas self-generation and high organic matter,the problems in lithology identification,stratification,drilling of horizontal wells and improving drilling rate are solved by means of the changes of energy spectrum parameters and derived parameters.A formula for calculating the total organic carbon content in the Shixi syncline area of northern Guizhou is developed by fitting the optimized uranium and gamma data of energy spectrum parameters.A shale gas interpretation template is established by combining the changes in gas logging total hydrocarbon values.Practical application has shown that this method achieves rapid interpretation and evaluation of reservoir fluids,division of strata,determination of sedimentary environment,assistance in target entry,and improvement of reservoir drilling encounter rate.This method can be applied to similar blocks.