【作者】 王峰；

【导师】 温庆志；

【作者基本信息】 中国石油大学(华东) ， 油气田开发工程， 2017， 硕士

【摘要】 大牛地气田属于致密砂岩气藏,有效渗透率低于低于0.1×10~3μm~2,储层孔隙结构特征表现为低孔、细喉-微细喉的特征,具有低孔、低渗、低产的特点,在未经过压裂改造难以实现有效开发。随着长时间的开采,大牛地开发有利区砂体及气层厚度逐年变薄,水平井压后无阻流量逐渐下降,现有常规压裂技术已无法满足水平井进一步提产。需要在大牛地致密砂岩储层实施缝网压裂,才能有效保持高产稳产的状态。本文在大牛地储层岩石力学参数的基础上,建立射孔井井周应力模型,分别就井眼直径、射孔方位角、射孔相位角、射孔穿深、孔眼直径以及射孔密度对井周应力以及破裂压力的影响做出研究,得到相位角和方位角对破裂压力有明显影响,射孔方位在0°及180°时,相位角在60°或更小时,地层破裂压力最小,地层更易起裂。通过物理模拟实验,得到能压开模拟岩块的最低实验排量为10mL/min,并折算为现场中压开岩层的排量。通过物模实验研究了射孔位置与天然裂缝夹角对裂缝扩展形态的影响,当夹角达到60°或更大时,水力裂缝既会沿着天然裂缝扩展,也会穿过天然裂缝扩展,有利于缝网结构的形成。在模拟多段多簇水平井压裂的裂缝扩展模拟状态时,将经典的基于断裂力学的裂缝扩展模型进行了发展,用三角形非结构化网格对裂隙岩体进行单元离散,采用有限元方法计算位移场、应力场,采用远场围线积分计算裂尖应力强度因子及裂纹开裂角,对开裂单元进行网格分裂或节点移动,实现裂缝扩展的数值模拟。研究发现,裂缝延伸过程中存在偏转现象,三簇压裂中间缝基本沿直线延伸,两边缝受应力干扰影响,向最小水平地应力方向发生一定偏转。段内两簇裂缝压裂簇间距40m,三簇压裂簇间距20m时,裂缝能够发生理想的偏转形态。通过本文对大牛地致密砂岩储层的地应力状态进行研究,并以此为根据,对大牛地水平井多段多簇压裂进行裂缝扩展模拟,对现场提供一定的指导作用。更多还原

【Abstract】 Daniudi gas field belongs to tight sandstone gas reservoir.The effective permeability is lower than 0.1×10~3μm~2,and the pore structure of reservoir is characterized by low porosity,fine throat-fine throat.It is difficult to achieve effective development without fracturing.With long time mining,Daniudi development advantageous area of sand body and reservoir thickness gradually thinning.Horizontal wells after fracturing in the flow decreased gradually,the existing conventional fracturing technology has been unable to meet the level of wells further output.In the tight sandstone reservoir in Daniudi area,the fracture can be kept high and stable after the fracture of the network.This paper selected reservoir rock mechanics parameters,and establish well circumferential stress model of perforated well,respectively,the hole diameter,perforation orientation,perforation phase angle,perforation depth,perforation diameter,perforation density of well circumferential stress and fracture pressure are analyzed,only the phase angle and the azimuth angle have significant effect perforation orientation at 0 degrees and 180 degrees.The phase angle at 60 degrees or more hours minimum fracture pressure.Through physical simulation experiments,experimental displacement determine fracturing in tight sandstone gas reservoir in Daniudi 10mL/min,according to the formula into the field of displacement,respectively 10 meters and 100 meters fracturing,200 meters,a displacement of 4.565.42m~3/min,4.96.According to the formula into the field displacement,respectively,corresponding to the fracturing section 10 m,100 m,200 m displacement of 4.56,4.96,5.42m3/min.Finally,the influence of the perforation location and the natural crack angle on the crack propagation is analyzed by the physical model experiment.When the angle is 60 degrees or more,the hydraulic fracture will extend along the natural fracture,and it will extend through the natural crack.The classical crack fracture mechanics based on the extended model was developed using triangular unstructured grid of fractured rock mass is discrete,finite element method is used to calculate the displacement field and stress field,using the contour integral calculation of crack tip stress intensity factor and crack initiation angle,grid division or mobile nodes on the cracking unit numerical simulation of the crack propagation.And the influence of different parameters on the crack propagation in the multi-step and multi-stage fracturing of fracture network is analyzed.In the process of crack extension,there exists the phenomenon of steering,and the middle seam extends along the straight line.Both sides of the seam are affected by stress interference,and the direction of the minimum horizontal stress is deflected.When the length of the fracture extends to 60m,it is less affected by the stress interference,and then extends to the direction of maximum horizontal stress.Different cluster spacing can lead to different fracture deflection strength.The recommended spacing of two clusters is40m,and the recommended distance between the three clusters is 20m.On the basis of the stress state of Daniudi tight sandstone reservoir,the simulation of crack propagation in Daniudi horizontal well provides some guidance for the field.更多还原