基线选取对DSC法测试原油含蜡量的影响

Effect of baseline selection on wax content of crude oil tested by DSC method

差示扫描量热法(Differential Scanning Calorimetry,DSC)中基线的选取对原油析蜡潜热及含蜡量的测试计算结果有较大影响。针对目前基线选取不统一的问题,采用DSC法对大庆油田两个采油区块的原油进行测试计算,获得了原油降温过程的DSC曲线。分别采用两种常用的基线选取方法对两油样测得的DSC曲线进行分析并计算含蜡量。与氧化铝吸附法测得的含蜡量的对比结果表明:采用内插基线法处理测试结果时,两油样的相对误差分别为4.7%和-3.1%;采用反向延长线法处理测试结果时,两油样的相对误差分别为52.6%和34.7%。因此,利用DSC法测量原油析蜡潜热及含蜡量时,采用反向延长线作基线的测试计算结果误差过大,宜采用内插基线法确定基线。

When the Differential Scanning Calorimetry（DSC） is used for testing wax content and latent heat of wax precipitation in crude oil, the calculation results are more affected by the selection of baseline. To deal with the inconsistency of baseline selection, the crude oil of two oil production blocks in Daqing Oilfield was measured by the DSC method, and the DSC curves of crude oil cooling were plotted. Then, the DSC curves of two oil samples were analyzed by two commonly used baseline selection methods to calculate the wax contents. The calculated wax contents were compared with the values measured by alumina adsorption method. It is shown that the relative errors of two oil samples are 4.7% and-3.1% respectively when the testing results are processed by means of interpolation baseline method. And the relative errors are 52.6% and 34.7% respectively when the reverse extension line method is adopted. To sum up, the interpolation baseline method is more suitable for baseline determination when DSC is used to measure wax content and latent heat of wax precipitation in crude oils, while the calculation results with the reverse extension line as the baseline are of great errors.