Shale hydrocarbon-type analysis

The classical silica gel chromatographic method for determination of percent olefins in shale oils was studied and found wanting, mainly because of cross-contamination from high levels of olefins and heteroatom-containing compounds. This paper describes a new hydroboration/oxidation procedure for olefins, and reports its use in hydrocarbon-type analysis of both whole shale oils and distillate fractions. Percent composition values for three whole oils ranged as follows saturates, 13-26 olefins, 16-20 aromatics, 5-14 polar compounds, 41S2. A discussion of IR analysis for relative amounts of specific olefin types such as terminal, internal trans, and methylene structures is included. 

Work in the area of hydrocarbon-type analysis, i.e. saturate, olefin, and aromatic, has been conducted at the Laramie Energy Research Center (LERC) for over two decades. During this time, a significant portion of the eflFort has been directed towards the quantification and characterization of the various types of olefins found in Green River Formation shale oils and their distillate fractions (1-9). 

This chapter presents a close look at the standard silica gel analysis of a shale oil naphtha with an evaluation of its effectiveness, a description of the new method now used to quantify olefins in shale oil products, a summary of results of the hydrocarbon-type analysis using the new method for a series of three related shale oils, and a discussion of the information on olefin-type compounds which can be revealed by IR examination of whole shale oils. The paper concludes with a brief discussion of additional applications of the hydroboration of olefins to problems of interest to the petroleum analyst. 

As with all shale oils, the polar material first must be removed from the oil prior to hydrocarbon-type analysis. The procedure shown in Figure 1 was applied several years ago to shale oil distillates in the boiling ranges 200°-325°C and 325°-S00°C (9). The technique made use of added internal standards and GC comparison of sample-internal... 

Table I. Hydrocarbon-Type Analysis of Shale Oil Distillates...

The classical silica gel olefin analysis was evaluated with respect to shale oil products and found wanting. A new approach to olefin analysis using mild, olefin-modifying reagents was described and partially demonstrated for shale oil distillates and whole oils. Hydrocarbon-type composition data and a discussion of IR analysis for various types of olefinic compounds were presented for three whole oils. 

Compositional analysis is concerned with determining structural relationships in the molecules present in a sample. Inhared spectroscopy is the most commonly used tool for qualitative chemical analysis of viscous oils. Descriptions and tables of characteristic absorbance for a variety of organic functional groups are readily available in many textbooks. Techniques for quantitative anal3rsis for many additives and some hydrocarbon types are available, although few have been issued as ASTM standards. Reports on new methods are commonly reported in the chemistry literature. To locate information on new analytical methods, a most useful reference is the bi-aimual Application Review published by the American Chemical Society. These have appeared recently in the June 15 issue of Analytical Chemistry in odd-numbered years. Recent reviews cover coal, crude oil, shale oil, heavy oils (natural and refined), lubricants, natural gas, and refined products and source rocks. Extensive references to original research papers are provided. A complimentary Fundamental Review covering the basic analytical techniques is published in even-numbered years. 

Fig. 1. Simplified evaluation strategy for top seal assessment. The flow chart begins by determining if faults throws are greater than the top seal thickness. If so, then a fault seal analysis is an additional requirement. Top seals are simplified into three main types (1) massive shale, (2) layered shale/sand/silt, and (3) massive strata of other coarser grained lithologies. Key top seal risks and the data required to carry out their assessments are shown in the flow chart. The rectangles represent leakage scenarios and the ellipses indicate data which will contribute to analysis of the scenarios (abbreviations Fluid P, formation fluid pressure <5 hor, minimum horizontal stress Entry P, capillary entry pressure HC prop s, hydrocarbon physical properties, including wetting characteristics).

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