Development and Application of Flushing Fluid Used for Shale Gas and Tight Gas

In the process of drilling horizontal Wells such as shale gas and tight gas, oil-based mud is used, which makes it difficult to flush mud cake in cementing process and poor compatibility with cement slurry leads to poor cementing displacement efficiency and low cementing strength. In order to solve the problems above, the research of oil-based mud flushing fluid was carried out. By evaluating the permeability, solubility and flushing efficiency of a single agent, the efficient oil flushing fluid has been developed. The formula is: 5 wt.% APEO(TX-15) + 5 wt.% poly-ethylene glycol fatty acid esters (400DO) + 10 wt.% penetrating agent(JFC-T) + 5 wt.% penetrating agent (JFC-M) + 1 wt.% ethylene glycol butyl ether + 74 wt.% water. The flushing efficiency of oil-based mud at different concentrations and temperatures was investigated, and the flushing efficiency was all greater than 90%. The flushing efficiency of the spacer prepared by the flushing fluid was greater than 95%. It also has good compatibility with oil-based mud and cement slurry. The spacer has already been used in 5 Wells with high cementing quality.