API REPORT 81-43
Analysis of Trace Metals in Drilling Fluid Barite
|Publication Date:||1 June 1982|
An increased need for accurately measuring the concentrations of potentially toxic trace metals in drilling fluid barite led the American Petroleum Institute to develop a series of standard methods for the analysis of As, Cd, Hg and Pb (Clarke, 1981). To aid in this endeavor, our study sought to thoroughly review and revise, as appropriate, these procedures and still achieve the desired detection limits of 0.1 ppm for As, Cd and Hg and 1 ppm for Pb.
The initial focus of our work (reported in Section II) was to check for metal losses during sample digestion and to evaluate the efficiency of the technique (i.e. determine the percent of the total metal removed by the proposed API method). This first task was addressed by comparing data from our closed-system, "teflon bomb" technique (using ≤ 0.05 g samples) with the more conventional leaching methodology proposed by API (with 0.5 to 10 g samples). Armed with the results of this comparison and a first-hand crack at the proposed procedure, we go on in Section III to provide some suggested revisions (with justifications) for these already rather well worked out methods. During the study, three (3) distinctly different barite samples (supplied by API) were used; they are (1) Battle Mountain Barite, (2) Test Calibration Barite, and (3) Dirty Barite.