微心PDC钻头心部结构优化的实验研究

Experimental Study on Optimization of Core Structure of Micro-core PDC Bit

在油气勘探中,需要在地层中进行岩石取样同时保证钻头的破岩效率和机械钻速,因此需要对微心PDC钻头心部结构进行优化。通过在不同尺寸的3种不同岩性(砂岩、灰岩和花岗岩)的岩心柱上完成静压、折断、冲击3种破坏形式的破岩实验,设计及制造一只直径为152.4 mm的可变参数的微心PDC钻头,并在不同尺寸的砂岩岩心柱上完成室内台架实验。实验结果表明:折断的破岩效率最高,静压其次、冲击最小;与全覆盖的钻头相比,微心PDC钻头机械钻速提高49%~112%;微心PDC钻头岩柱的高度对钻头的机械钻速影响较小,而岩柱的直径对机械钻速影响较大;微心PDC钻头在3种岩样中均能实现体积破碎,产生大岩屑,能提高破岩效率和机械钻速,并得到3种破岩方式下的最优岩心柱尺寸。

In oil and gas exploration,rock sampling is required in the formation while ensuring the rock breaking efficiency and mechanical drilling rate of bit. Therefore,it’s necessary to optimize the core structure of micro-core polycrystalline diamond compact(PDC) bit. Rock-breaking experiments which contain three rock-breaking modes(static-pressure damage, fracture damage, impact damage) are conducted on sandstone, limestone,and granite core columns. A variable micro-core PDC bit with a diameter of 152.4 mm is designed and produced,which is used to conduct laboratory experiments on multiple-sized sand stone core columns. The experimental results show that the fracture damage has the highest penetration rate, followed by the static-pressure, then the impact damage. The rate of penetrate(ROP) of micro-core PDC bit increased by 49-112%,compared to the full-cover bit. As for micro-core bit,the height of the core column shows less influence on ROP,while the diameter of the core column shows remarkable influence. The results show that the micro-core PDC bit can achieve volume breakage on three kinds of rock specimens,produce large debris,improve the rock breaking efficiency and ROP,and the optimal size of core columns under the three rock-breaking modes is obtained.