Paper: Steve Metcalf, BJ Services Co.

A great many carbonates are stimulated successfully utilizing acid fracturing techniques. There are several models in the industry, which will give relative comparisons of fluid performances under varying reservoir conditions. These are only good as design tools when validated. However, a great deal of laboratory time is spent testing rocks and fluids for reactivity, diffusivity and leak-off to provide the values for these models. It is on most occasions difficult to comprehend the significance of these results.Presented are the variances in laboratory generated values and their effect on the output of one of the fracture acidizing models. Several reasons are addressed as to why these variances occur. These include the difficulty in measuring accurately the surface area of samples tested, the limited amount of reservoir rock to test with all the same properties and the limited amount of time to perform the tests.