American Association of Drilling Engineers (AADE)
April 12, 2016

Fluid-shale compatibility testing is as old as the drilling fluid industry itself. When drilling fluids started to be deliberately used for hole-making, the (in-)compatibility of these fluids with clay-rich shale formations became immediately apparent, and industry scientist have been trying to make sense of it all ever since. With a plethora of possible shale tests available, a key question remains: what are the best, most representative tests to characterize fluid-shale interactions and avoid making decisions based on less sensitive tests that may suffer from artifacts and yield misleading results?
This paper argues for the use of a representative set of shale tests that includes accretion tests, cuttings dispersion tests and mud pressure transmission tests, while pointing out issues and problems with other tests such as atmospheric swelling tests and capillary suction tests, which still find wide-scale application in the industry. Moreover, it introduces a novel, low cost borehole stability test in the form of a modified thick wall cylinder test. This new test exposes a cylindrical shale samples, confined under downhole temperature and pressure, to mud formulations at overbalance for a specified period of time and assesses the failure strength of the sample thereafter. The test is thereby capable of mimicking the results of much more sophisticated, and much more expensive, test protocols such as the downhole simulation cell test.
The details on the new test protocol are given here. Moreover, it is shown how the proposed test protocol can be used to the comprehensive qualification of the merits of new nano-particle and high-salinity fluid formulations.

Authors: Eric Van Oort, Besmir Buranaj Hoxha, Arthur Hale, Munir Aldin, Robert Patterson, and MetaRock Laboratories, Inc.