R.J.M. Bonnie
Koninklijke/Shell Exploratie & Produktie Laboratorium, Shell Research B.V, Rijswijk, The Netherlands
ABSTRACT
Pulsed neutron capture (PNC) tools from various contractors have been tested in a well-conditioned laboratory test tank. Such testing is of importance in quantifying the accuracy of the tools when they are used to assess hydrocarbon saturations or changes therein during reservoir production. The present series of tests is an extension of experiments published previously. Five different tools from four contractors were used and a direct comparison is given between the data from the different tools. Furthermore, in the previous tests the porosity of the sandpack was rather high (43 p.u.), whereas in the present tests a more representative porosity of 22.9 p.u. has been obtained. The tests have been performed with various borehole fluids, two formation fluid salinities and two thicknesses of cement. The results clearly show that none of the tools provide the true formation capture cross-section (Sintrinsic) with sufficient accuracy for all conditions, i.e., with all the tools, residual borehole effects remain, even after full data processing at the logging companies’ computer centres. It is concluded that it is still not possible to measure the absolute value of Sintrinsic accurately in all logging conditions.