The flushing efficiency of a cementing ahead fluid is one of the key factors affecting the job quality of well cementing.A reasonable method for evaluating the flushing efficiency of an ahead fluid and a reasonable experimental object are key factors for selecting ahead fluid formulation and volume.The evaluation results obtained with the methods presently in use for evaluating the flushing efficiency of ahead fluids cannot objectively and truthfully reflect the flushing effect of an ahead fluid.To solve this problem,cores made with pores of different depths are used as the experimental object to simulate the actual rough borehole walls,and a magnetic agitator is used to simulate the whole process of flushing action of the ahead fluid on the borehole wall.The cores with pores and the magnetic agitator composed of the new evaluation method and the feasibility of this method is verified.The experimental results obtained show that this new method can simulate the real situation of the uneven borehole walls and takes into account the effects of several factors,such as the detention and adsorption of the barite particles in the drilling fluid and the spacers in the pores and on the surface of the borehole walls.The evaluation results are regarded as being more objective and are able to truthfully reflect the flushing effect of an ahead fluid,and they can be used as the technical reference and the bases for optimization of ahead fluid formulation and for volume design of an ahead fluid.Using this method,the flushing efficiencies of several ahead fluids of different densities and contact time lengths are evaluated.The evaluation test gives results that are repeatable,and objectively and truthfully reflect the performance of the flushing additives.With this method,the composition and volume of an ahead fluid for cementing a well drilled in a gas field in East China Sea is optimized and modified.The flushing efficiency of the ahead fluid after optimization is 97%,and the job quality of the well cementing operation is improved by 10.3%.
Well cementingAhead fluidEvaluation methodFlushing efficiency
国家科技期刊平台
NSTL
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