| Abstract |
The main objective of the feasibility study was to test the hypothesis that properly plugged wells are effectively sealed by drilling mud. While achieving such an objective, knowledge of the dynamics of building mud cake on the wellbore-face is obtained, as well as comprehension of changes that occur in drilling mud from the time it is placed in a well until it reaches equilibrium. A system was developed to simulate (a) building mud cake in a borehole, (b) plugging the well, and (c) injecting salt water into a nearby well, with concomitant migration of salt water into the plugged well. The system 'duplicates' reservoir pressures, mud pressures, and reservoir-formation characteristics that develop while mud cake is built, as in drilling a well. Salt-water injection is simulated, to monitor any fluid migration through the reservoir. A 2100-ft. well and ancillary equipment was constructed to permit controlled measurement and variation of simulated depth, porosity and permeability of reservoir rock, fluid composition, fluid pressure, injection pressure, and mud properties. Data can be recorded continuously by computer. The in-place system provides for extensive testing of the many variables that influence effective plugging of boreholes with drilling mud. |
