剪切增稠流体对裂隙地层的封堵特性试验研究

Experimental study on the sealing characteristics of fractured formation by shear thickening fluid

摘要:

裂隙性地层存在的裂缝型漏失通道通常具有多尺度特性和不确定性，钻井液漏失问题在裂隙性地层进行地质钻探施工中尤为突出。剪切增稠流体（Shear Thickening Fluid， STF）作为一种新型智能材料，具备自感知、自适应和自修复等优良特性，目前已在多领域得到广泛应用。本研究将剪切增稠流体作为一种堵漏材料，通过API堵漏仪单缝管封堵试验，探究了剪切增稠流体在不同分散相浓度（56.9vol%、59.2vol%和61.7vol%）、缝宽（1、2、3、4、5 mm）和压力条件下对裂缝的封堵特性。封堵试验结果表明：漏失量会随着缝宽和时间的增加而增加；纳米SiO₂浓度在56.9%~61.7%范围内增加时，会降低漏失速率并减弱缝宽对漏失速率的影响程度；当漏失压力为0 MPa时，剪切增稠流体不产生增稠效应，以液态形式从缝内漏失，压力小幅度增加时会激发其增稠效应，产生团聚状颗粒对缝管进行封堵降低漏失速率；当压力进一步增大超过封堵层承压能力时，剪切增稠流体以板状形态被挤出裂缝。研究剪切增稠流体在堵漏领域的应用，有望为裂隙性地层堵漏提供创新解决方案。

Abstract:

The fracture leakage channel in fractured formation usually has multi-scale characteristics and uncertainty. The drilling fluid leakage problem is particularly prominent in the construction of geological drilling in fractured formation. Shear Thickening Fluid （STF）， as a new type of intelligent material， has excellent properties such as self-sensing， self-adaptation and self-repair， and has been widely used in many fields. In this study， shear thickening fluid was used as a plugging material， and the plugging characteristics of shear thickening fluid were investigated under different dispersed phase concentrations （56.9vol%， 59.2vol% and 61.7vol%）， slit widths （1，2，3，4，5mm） and pressure conditions through the plugging test of API plugging instrument. The plugging test results show that the amount of leakage increases with the increase of seam width and time. When the concentration of nano silica increases in the range of 56.9%~61.7%， the leakage rate will be reduced and the effect of the gap width on the leakage rate will be weakened. When the leakage pressure is 0 MPa， the shear thickening fluid does not produce thickening effect， but leaks out from the seam in the form of liquid. When the pressure increases slightly， the thickening effect will be stimulated， and agglomeration particles will be generated to seal the seam pipe and reduce the leakage rate. When the pressure further increases beyond the bearing capacity of the sealing layer， the shear-thickening fluid is extruded out of the fracture in a plate form. The application of shear-thickening fluid in plugging field is expected to provide innovative solutions for plugging in fractured formation.