Research on a Polygonal Quartz Sand Flushing Fluid for Cementing Oil and Gas Wells and Its Field Application

Conventional flushing fluid cannot effectively remove the filter cake from the well walls during oil and gas wells cementing, especially oil-bearing filter cakes formed by oil-base drilling fluid on the well walls and the oil film attached to the casing walls, both of which seriously affect cementing quality. Therefore, it was hypothesized that polygonal quartz sand particles with sharp corners and irregular shapes mixed into an ideal suspending agent would strengthen the physical scouring capabilities of flushing fluid. With that in mind, a polygonal quartz sand flushing fluid was prepared. The laboratory test revealed that the prepared flushing fluid was highly stable and compatible with the cement slurry and drilling fluid, and the flushing efficiency was higher than that of conventional flushing fluid by 10 to 30 percentage points. After the successful laboratory results, the prepared flushing fluid was successfully applied in four wells in Shengli Oilfield, and the cementing quality was significantly improved. The research and application indicated that the prepared flushing fluid could effectively remove the filter cake, oil film, and cuttings on the well walls and improve the cementing environment of the cement-formation interface. In this way, the cementing quality was enhanced to meet the requirements of large-scale fracturing for the cementing quality of cement sheaths.