A NEW METHOD TO IMPROVE THE ACCURACY OF ACOUSTIC PRESSURE CALCULATIONS

Acoustic pressure measurements can be an important surveillance tool in oil fields undergoing waterflood and enhanced oil recovery schemes. They offer a cost-effective method for measuring subsurface pressures in pumping oil wells without the expense of pulling the rods and pump. However, experience has shown that the accuracy of subsurface pressures obtained from fluid-level calculation has, at times, proved questionable. Data from several well studies is presented that shows the average difference between standard acoustic pressure calculations and directly measured subsurface pressures is approximately 10%. Furthermore, a new method of calculating acoustic pressures is described. The new approach was applied to test data from nine producing oil wells in Alberta. All wells were chosen from either waterflood or miscible flood projects. For this particular set of well tests, the new procedure reduced the average difference between acoustic and directly measured pressures to within 1%. The new calculation method extends the applicability of the method described in the ERCB Guide G-5(1) to a wider range of oil compositions. The new method also addresses some of the concerns raised in the Guide G-5 and improves the accuracy of acoustic pressure calculations in waterflood and miscible flood projects.