围压条件下PDC异形齿切削硅质白云岩研究

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Cutting of Siliceous Dolomiteby Special-Shaped PDC Cutter under Confining Pressure

Tian Wanqing1 Liu Weiji²Qin Dehong1 Liu Chenglong1Wang Haitao1Hu Hai² （1.PetroChina TarimOilfield Company;2.SchoolofMechanical Engineering，Southwest Petroleum University）

Abstract： The dolomite formation is an importantfield for oiland gas exploration inthe future.However，due to the high confining pressure environment in wellbore and thehard-to-drillcharacteristics of dolomite，traditional planar cuter PDC bit is prone to problems such as cuter breakage and loss when drillng in dolomite formations， making it dificult to meet the requirements of effcient drilling.To provideanew idea forthe cuterlayout of PDC bit thatcan eficientlydrill dolomite formations under confining pressure，basedon the independently developed rocking cutting and breaking device of true triaxial PDC cutter，taking siliceous dolomitecolected in the Tarim Basin as the test object，4 types of PDC cutters were selected to carry out indoor cuting tests under confining pressure.Moreover，the mass fraction，surface roughness，，fractal dimension and cutting force ofcuttings obtained aftera single cut were studied，andthe rock-breaking specific energyof different PDC cutters was compared.The research results show that the cuting force curves of axe-shaped cutter and multi-edged cutter are relatively smooh，with smallfluctuations，and the peak value of cutting force is also smaller.At a cutting depth of 1.0mm ，observed from the roughness index and fractal dimension ofcuttings，the axe-shaped cuter has the strongest ability tocause large volumebreakage，anditsrock breaking abilityis least affected byconfining pressure，folowed by the multi-edged cuter.The rock breaking abilityof conical cutteris most affected byconfining pressure.When theconfining pressure is not lessthan 15 MPa，the rock-breaking specific energy of conical cutter is the largest，followed by flat cutter，multi-edged cutter and axe-shaped cutterinturn.The research results providea theoretical basis for designing aggressive，impact-resistant and abrasion-resistantPDCbit cutterlayouts applicable to dolomite formations.

Keywords： PDC bit；dolomite； special-shaped cutter;confining pressure;；cutting force；rock-breaking specific energy； fractal dimension；roughness index

0 引言

据统计，世界上大约1/3的油气资源蕴藏在超深层（埋深大于 6000m ）碳酸盐岩中，其中又有1/2是白云岩[1]。（剩余9868字）