Adsorption Characteristics Of Shale Gas On Carboniferous In Eastern Qaidam Basin

Contradiction of international energy supply and demand is prominent recently.shale gas has enormous resource potential. It is a clean, efficient and unconventionalenergy. United States and Canada has achieved commercial exploitation of shale gas.Investigation of our country is still in its infancy. Accelerate the development of shalegas has great significance for alleviating the shortage of the oil and gas resources.Carboniferous strata distributes widely in the east of Qaidam Basin whichcontains a lot of organic carbon and the metamorphic grade is moderate.Carboniferous strata is a high-quality source rock with great hydrocarbon potential.For a long time, few studies of this source rock has seriously hinder the exploration ofoil and gas in Qaidam Basin.In this paper, according to the experimental principle and requirements, wecarried out methane adsorption/desorption characteristics experiments of6shalesamples from ShiQian1Well and ZK1-1well in eastern Qaidam Basin. On the basisof sample s39in30℃,40℃and60℃isothermal adsorption experiments, wefound that the isosteric heat decreased with increasing adsorption capacity and thespecific relationship isq=-3679.7n+9779.5. Using isosteric heat and experimental data ofsample s39in40℃, we calculated the isothermal adsorption value at50℃throughClausius-Clapeyron equation. Calculated values were in good agreement with theexperimental data. Matlab was used to do nonlinear regression analysis of the ninegroups of experimental data with Langmuir-Freundlich model. We got a good fittingresult, and four parameters in the model were determined. The parameters had clearphysical meanings.The desorption of sample ZK2and s04were measured in30℃.We found that the curves of shale adsorption and desorption were not coincidence,and desorption existed hysteresis.Many factors affect shale gas adsorption including temperature, pressure, organiccarbon content, pore structure, clay content and thermal maturity, etc. The experiment results show that: methane adsorption capacity decreases withincreasing temperature. With pressure increases, the amount of methane adsorptionfirstly increased and then decreased. The relationship between adsorption capacity andorganic carbon content was approximately linear, correlation was97.59%. Adsorptioncapacity increased with increasing organic carbon content, clay content and thermalmaturity. Pore diameter distribution of shale was large, the amount of methaneadsorption and micropore volume was positively correlated. Shale had huge specificsurface area, and micropore was the main contributor. The relationship between shaleadsorption quantity and total specific surface area and micropore specific surface areawas positively correlated. The shape of the hysteresis loop reflected pore structure.Pore development of sample s39and ZK1is complex which had different levels ofpore diameter and various types of pore. Types of these pores mainly were the inkbottle and tablet. This kind of pore was poor connectivity, but favorable to theadsorption and a good reservoir.