Organic sulfur and nitrogen compounds in crude from Kotyrtas field

The work reported here was aimed at determining the group composition of sulfur and nitrogen compounds in certain crudes from the Kotyrtas field of the North Emba zone, taken from different wells and depths. Crudes from the Kotyrtas field are heavy (densities of 840.1-899.8 kg/m3) with the exception of the oil from Well 5 (782.7 kg/m3). The yield of naphtha cuts up to 200°C is 13.2-22.43% by weight for the heavy crudes, and 50.4% by weight for the light crude. These crudes can be classed as paraffinic type, with paraffinic hydrocarbon contents of 68.82-80.85% by weight and aromatics contents of 9.72-19.65% by weight. Thus, the crudes from the Kotyrtas field are for the most part low-sulfur with a small quantity of mercaptans - with the exception of the oil from Well 24, where the mercaptan sulfur content is 11.85% (relative). There is no disulfide sulfur or hydrogen sulfide in the samples that we investigated. In the crudes, and also in the distillation fractions, the sulfur compounds consist mainly of sulfide and residual sulfur. These crudes contain up to 0.83% total nitrogen and up to 0.4547% basic nitrogen. The concentration of nitrogen compounds and the concentration of mercaptan sulfur increase with increasing boiling point of the fraction.