Experimental Research On The Effect Of Mineral Substance On Hydrogen Sulphide Formation During Thermal Recovery

With high-temperature steam was injected into the formation in the process of steam in-jection thermal recovery,not only the viscosity of heavy oil decreased for the temperature rise,but also complex thermochemical reactions occurred between heavy oil,rock matrix and for-mation water,which generated acid gases such as CO₂ and H₂S.Mineral substance of rock matrix has an important impact on thermochemical reaction.Therefore,research the effect of mineral substance on H₂S formation rule during steam injection thermal recovery has great significance for H₂S prevention and control works to oilfield.This paper firstly carried out basic physical property tests to obtain elements or mineral compositions of crude oil,formation water and core of Liaohe Oilfield Wa-38,and found that sulfur-containing organic matter in heavy oil of Wa-38 1914 well is mainly composed of thi-oether,thiophene and its derivatives that have high thermal stability.Thermochemical simulation experiments in door of heavy oil in high-temperature and high-pressure reaction kettle showed that aquathermolysis of sulfur-containing organic matter is the main way to generate H₂S for heavy oil of Wa-38 1914 well.What's more,metal salts such as Al,Mg,Ca and Zn can reduce pH value of solution to strengthen the protonation ef-fect and catalyze aquathermolysis intermediate reactions such as C-S bond break,hydrodesul-furization and the water gas shift reaction?WGSR?,which thus facilitates aquathermolysis to generate H₂S,and Al³⁺has the best catalytic effect.Aquathermolysis experiments of model compounds showed that pyrolysis reaction of 2-methylthiophene,benzothiophene dibenzothiophene and thianthrene is not going to occur un-der the reaction temperature of 280?.Due to the different electron cloud density of the S at-om,aquathermolysis of thiophene compounds with different structure generate different rates of H₂S,2-methyl-thiophene>benzothiophene>dibenzothiophene>thianthrene.It is discussed the aquathermolysis ways of four kinds of model compounds,and indicated that the second-ary hydrolysis plays an important role in the process of generating H₂S by aquthermolysis for thiophene-sulfur-containing organic compounds,especially sulfur-containing organic com-pounds that can't produce aldehyde group in primary hydrolysis.Finally,TSR simulation laboratory experiments research showed that solid anhydrite can't trigger TSR reaction,which means that the precondition of generating H₂S by TSR reac-tion is to form a contact ion pair between sulfate ion and metal cation.The greater the charge number of metal cations in the solution,the easier to form contact ion pair,thus the more like-ly to occur TSR reaction.Based on simulation laboratory experiment research of thermochemical reaction with heavy oil and model compounds,the relevant conclusions derived from this paper provide scientific theoretical support for taking H₂S prevention and control measures in oil field,it has important significance.