用有限元方法模拟了不同形状钻头的破岩效果,研究了地层应力分布及裂缝延伸模式。按照国际钻井商协会（IADC）分类标准设计了14种钻头形状。设计了地层模型,给出了钻头尺寸、地层性质、网格划分方法和边界条件等。采用拟静态条件和质量缩放法以减少模拟时间、提高模拟精度。模拟结果表明,对于9种常用钻头形状,增加锥体高度高应力区面积会增大,而保径高度与产生的应力之间没有明显关系。减小保径高度,高应力区从鼻端和中心部位转移到保径区。对于非常用钻头形状,凸形钻头产生的应力场较大,双心钻头导眼体底部应力较集中。裂缝主要产生在保径区和鼻端,锥体高度和保径高度较大的钻头产生的垂直裂缝较长。使用平形和凸形钻头时没有产生较长的垂直裂缝。双心钻头可抑制保径区的垂直裂缝,却使地层更易出现水平裂缝,有中间段扩眼器的钻头造成的井壁损伤更小。图10表3参12
HEYDARSHAHY Seyed Ali
,
KAREKAL Shivakumar
. 钻头冠部形状对破岩效果的影响[J]. 石油勘探与开发, 2017
, 44(4)
: 630
-637
.
DOI: 10.11698/PED.2017.04.17
The influence of different bit profiles on possible fracture modes was investigated using Finite Element Method. The International Association of Drilling Contractors (IADC) classification was used to design 14 types of profiles. The formation model was built, with given bit size, formation properties, meshing method and boundary conditions, etc. Moreover, the pseudo-static state and mass scaling were used to reduce the simulation time and increase the simulation accuracy. The simulation results showed that, for nine common bit profiles, larger cone height led to larger area of high stress zone, and the gauge height was not apparently related to the stress generated. When the gauge height decreased, the high stress zone turned from the nose and center to the gauge zone. For the non-common bit profiles, the convex bit produced larger high stress field, and the pilot section bottom of bicentre bits had concentrated stress. Fractures were created in the gauge zones and noses, and the bits with larger cone height and gauge height induced longer vertical fractures. The flat and convex bits did not generate longer vertical fractures. The bicentre bit can hinder the vertical fractures in the gauge zone, but enables the horizontal fractures easier. The bit with intermediate reamer has less damage to sidewall.
[1] GERBAUD L, MENAND S, SELLAMI H. PDC bits: All comes from the cutter/rock interaction[R]. SPE 98988, 2006.
[2] PRYHOROVSKA T O, CHAPLINSKIY S S, KUDRIAVTSEV I O. 聚晶金刚石钻头切削齿切削岩块过程的有限元模拟[J]. 石油勘探与开发, 2015, 42(6): 812-816.
PRYHOROVSKA T O, CHAPLINSKIY S S, KUDRIAVTSEV I O. Finite element modelling of rock mass cutting by cutters for PDC drill bits[J]. Petroleum Exploration and Development, 2015, 42(6): 812-816.
[3] OHNO T, KARASAWA H, KOBAYASHI H. Cost reduction of polycrystalline diamond compact bits through improved durability[J]. Geothermics, 2002, 31(2): 245-262.
[4] WELLS M, MARVEL T, BEUERSHAUSEN C. Bit balling mitigation in PDC bit design[R]. SPE 114673-MS, 2008.
[5] GLOWKA D A. Use of single-cutter data in the analysis of PDC bit designs[J]. Journal of Petroleum Technology, 1989, 41(8): 850-859.
[6] PAIN D D, SCHIECK B E. Evolution of polycrystalline diamond compact bit designs for rocky mountain drilling[J]. Journal of Petroleum Technology, 1985, 37(7): 1213-1219.
[7] WINTERS W J, DOIRON H H. The 1987 IADC fixed cutter bit classification system[R]. SPE 16142-MS, 1987.
[8] WEI Z, WANG Y, CHEN Z. Design of PDC bit for lower layer in Binhai block Dagang oilfield[C]//Proceedings of the 2011 International Conference on Transportation, Mechanical, and Electrical Engineering. New York: IEEE, 2011: 232-235.
[9] JU P, WANG Z, ZHAI Y, et al. Numerical simulation study on the optimization design of the crown shape of PDC drill bit[J]. Journal of Petroleum Exploration & Production Technology, 2014, 4(4): 343-350.
[10] AL-THUWAINI J K, EMAD M, HENDRAZID H, et al. Combination of unique stabilized Bi-Center bit and vibration dampening tool improve hole opening performance through interbedded formations in Saudi Arabia[R]. SPE 117248-MS, 2008.
[11] Dassault Systémes Simulia Corp. ABAQUS theory manual[M]. Providence, RI, USA: Dassault Systémes Simulia Corp., 2012.
[12] JANKOWIAK T, LODYGOWSKI T. Identification of parameters of concrete damage plasticity constitutive model[J]. Foundations of Civil and Environmental Engineering, 2005, 6(1): 53-69.
