Drill Bridge Plug with a New Fluid in Coiled Tubing Operations in Well JY25-1HF

When drilling the bridge plugs in coiled tubing operations, the limitations from the coiled tubing equipment and the drilling fluids always hinder the return of drilled cuttings which in turn causes problems such as overpressure pumping and pipe sticking etc. To avoid these problems, a polysaccharide polymer has been introduced into the drilling fluid, and, by carefully select materials used in the drilling fluid and performance evaluation, a new drilling fluid has been developed for use in the drilling of bridge plugs. As a power law fluid, the pipe flow of it is of turbulent flow, and flow in annular space is of laminar flow, showing stark contrast with the old drilling fluid which is of turbulent flow both in annular space and in pipe. The new drilling fluid has circulation pressure losses of 1.7 MPa and 0.116 MPa in pipe and in annular space, respectively, while the circulation pressure loss of the old drilling fluid is 0 MPa both in pipe and in annular space. The new drilling fluid has been tried in Well JY25-1HF. The highest pump pressure, 1.80 MPa, was achieved when pumping 10 m³ drilling fluid into the hole, very close to the calculation, with an error of 1.80%. The application of the new bridge plug drilling fluid has demonstrated that it has better carry capacity, more than 3 times of the old drilling fluid, and can be introduced to other area where bridge plugs are to be drilled.