钻井液组分对泥饼抗剪强度的影响

Effect of Composition of Drilling Fluid on Filter Cake Shear Strength

钻井液组分直接影响井内泥饼的成分和性质,并最终影响隔层界面处泥饼的力学性能。为研究钻井液不同组分对泥饼抗剪强度的影响机理,综合运用土的重塑和直剪实验,分别测量膨润土重塑土、膨润土-铁矿粉重塑土、膨润土-石英砂粉重塑土的抗剪强度指标,研究钻井液泥饼中的黏土矿物、加重材料和钻屑3类固相物质对界面泥饼的抗剪强度影响。结果表明,在一定含水率和压实程度下,随着泥饼中铁矿粉含量的增大,泥饼的内摩擦角和黏聚力均线性减小;当泥饼中石英砂粉质量分数低于10%时,泥饼的内摩擦角和黏聚力均线性减小;而当泥饼中石英砂粉质量分数高于10%时,泥饼的内摩擦角、黏聚力变化不大;一定范围内,泥饼中膨润土含量增加有利于提高泥饼黏聚力。

Drilling fluid composition directly affects the composition and property of filter cakes, which in turn affect the mechanical performance of the filter cakes at interlayer interface. Shear strengths of several clay samples, such as pure bentonite, bentonitehematite manipulated clay, and bentonite-quartz powder manipulated clay were measured to study the effect of three solids(clay, weighting agent and drill cutting) on the shear strength of filter cakes at the interlayer interface. The study showed that, at certain water content and compaction condition, the angle of internal friction and cohesive strength of filter cake linearly decreased with an increase of hematite content in filter cake. When mass ratio of quartz powder in filter cake was less than 10%, same result as hematite was obtained. When mass ratio of quartz powder in filter cake exceeded 10%, the angle of internal friction and cohesive strength of filter cake remained almost constant. Cohesive strength of filter cake increased with an increase of bentonite content in filter cake at a certain range.