The problems of low drilling efficiency and low core recovery due to borehole collapse were solved with pulling in casing while drilling through using combined BHA with casing.
采用组合钻具进行跟管钻进，通过随钻跟入的套管保护孔壁，解决因钻孔垮塌导致钻探效率和岩心采取率低等技术难题。
Increased core rate and to maintain borehole stability obtained is crucial to fully evaluate the oil shale.
提高取心率与保持井壁稳定性是对油页岩充分评价的关键性技术。
During course of in situ stress measurement, some problems such as core discing, minification and caving of borehole due to horizontal stress are appeared, and their mechanism is studied.
在现场地应力测量过程中发现了岩芯饼裂、钻孔径缩和钻孔破碎塌孔等现象，分析了这些现象的力学机理。
In the case of scientific deep-drilling Wells, therefore, it is desirable to combine borehole methods with core-based methods to obtain a complete three-dimensional in-situ stress.
所以，在以科学研究为目的的钻井工程中，最好能够结合钻孔法和岩芯法得到三维地应力的大小和方向。
In the case of scientific deep-drilling Wells, therefore, it is desirable to combine borehole methods with core-based methods to obtain a complete three-dimensional in-situ stress.
所以，在以科学研究为目的的钻井工程中，最好能够结合钻孔法和岩芯法得到三维地应力的大小和方向。
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