固井过程中井壁虚泥饼的可冲刷性研究

井壁泥饼的存在对固井质量的影响很大,往往会造成水泥环第二界面胶结变差,引起油气水窜,破坏井筒密封完整性。从流体的剪切应力出发,分析了水泥浆在偏心环空下产生的壁面剪应力大小。并利用水利工程中河流泥沙起动理论,分析了要冲刷掉泥饼需要的临界起动剪应力。最后通过比较环空各处2个力的大小,确定环空泥饼的可冲刷性。能够清晰反映固井过程中环空每个周相角下和整个环空的泥饼可冲刷性。研究表明,泥饼颗粒和厚度对泥饼可冲刷性影响很大,套管偏心也会对其产生影响。

Erodability of False Filter Cake on Borehole Wall During Well Cementing

False filter cake on borehole wall has great influence on the job quality of well cementing, often causing the cementation of the interface between cement sheath and borehole wall to become deteriorated, and resulting in fluid channeling. The shear stress on the borehole wall caused by cement slurry in eccentric annular space is analyzed. With the help of river sediment flow dynamics in hydraulic engineering, the critical starting shear stress necessary for the removal of filter cake is calculated. By comparing these two shear stresses in annular space, the erodability of false filter cake in the whole annular space can be determined. It is shown that the particle size distribution and the thickness of filter cake greatly affect the erodability of the filter cake, and the eccentricity of casing string also plays a role in this aspect.