维持页岩井壁稳定的物理封堵模拟和化学抑制实验研究

Physical plugging simulation and chemical inhibition experiment for wellbore stability in shale

页岩气作为一种储量巨大的非常规能源,是实现现代多元能源体系的重要一环。本文采用HKY-3压力传递实验仪研究不同盐溶液对页岩井壁稳定的影响规律。此外,基于离散元颗粒流模型,重构纳米颗粒拖拽力,模拟流体粘度及颗粒粒径、浓度、形状对页岩孔隙封堵效率。结果表明:(1)物理封堵方面,颗粒大小和浓度明显影响封堵效率,当颗粒最大值小于孔隙出口时,颗粒粒径由出口尺寸的1/5增加到出口尺寸的1/3和1/2时,孔隙封堵效率分别增加13%和23%。(2)流体物性对页岩纳米孔隙的封堵效果表明,粘度5 mPa·s时纳米颗粒封堵效率比1 mPa·s时高16.26%。(3)化学抑制方面,阻滞页岩孔隙压力传递的最佳的盐溶液及其浓度为20%HCOONa。研究成果可为适用于龙马溪组页岩钻进的水基钻井液体系遴选提供理论和技术基础。

Shale is a typical low‑permeability sedimentary rock,and wellbore stability in shale has always been a difficult and hot spot in shale gas(oil)exploration and development at home and abroad.In this paper,experimental testing,microscopic observation,theoretical analysis and numerical simulation are used to study the influence of salt solutions on the physical‑chemical seepage performance of shale under shale pressure transfer experiments.Furthermore,a numerical simulation model is provided to program and reconstruct the mechanical model of particles in nanopores,and to simulate the influence of particle size,concentration,shape and fluid viscosity on shale pore plugging efficiency.The results show that:(1)Particle size and concentration can affect plugging efficiency in terms of physical plugging.When the particle size does not exceed the outlet size,with increase of the particle size from 1/5 to 1/3 and 1/2 of the outlet size,the particle blocking effect increases by 13%and 23%as particle concentration is 5wt%.(2)Change of fluid physical properties affects shale nanopore plugging.The plugging efficiency of 5 mPa·s nanoparticle solution is 16.26%higher than that of 1mPa·s nanoparticle solution.(3)In terms of chemical inhibition,the best salt solution and its concentration to prevent the transmission of shale pore pressure are 20%HCOONa.The research results can provide a good theoretical and technical basis for the selection of water‑based drilling fluid systems suitable for Longmaxi shale drilling.