高密度钻井液加重材料沉降问题研究进展

钻井液的密度对于地层的压力控制至关重要，而流变性和沉降稳定性控制是高密度钻井液技术存在的主要技术难点之一。传统的加重材料，例如API重晶石在高密度钻井液中存在严重的沉降问题，对钻完井作业造成严重影响。不同粒径、形貌和比重的加重材料对改善高密度钻井液的流变性和沉降稳定性有不同的作用。综述了对API重晶石沉降问题的研究现状以及作为替代API重晶石的微粉加重材料的研究进展。国内外的室内研究与现场应用表明，高密度的微粉加重材料可有效解决高密度钻井液的沉降稳定性问题，并且具有降低摩阻、当量循环密度等优点。但是，微粉加重材料也存在固相控制、泥饼清除困难，微粉颗粒团聚的缺点，研究学者针对这些问题已展开大量研究，并提出相应解决办法。 

Progresses in Research on Settling of Weighting Materials in High Density Drilling Fluids

The density of drilling fluid plays a key role in controlling formation pressures, and the rheology and the settling stability of a high density drilling fluid, are technical difficulties always encountered in field drilling operations. Conventional weighting materials, such as API barites, tend to settle readily in high density drilling fluids, imposing serious negative effects on drilling/completion operations. Weighting materials of different particle sizes, morphology and densities play different roles in improving the rheology and settling stability of a drilling fluid. This paper summarizes the status quo of research work done to the settling of API barites and the progresses made in searching for micro powder weighting materials to replace API barites as drilling fluid weighing additives. Laboratory studies and field application both in China and abroad have demonstrated that micro powder weighting materials of high density are able to be used to address the settling stability problems associated with high density drilling fluids. These micro powder high density weighting materials also have the advantages of reducing friction and equivalent circulating density of drilling fluids. Problems associated with the use of micro powder weighting materials include difficulties in solids control and mud cake removal, and the glomeration of the micro particles of the weighting materials, which are now being addressed by many researchers all over the world.