Kinetic Study Of Carbon Isotopic In Natural Gas And Its Application

In Leshan-Longnvsi paleo-uplift area, Sichuan Basin, Kuqa depression, Tarim Basin and Kelameili gas field, Junggar Basin, accumulation period and the pool-forming efficiency of natural gas using the method of carbon isotope kinetics, this discussion focuses on Sichuan Basin. Combined with the geological conditions in the study area, select the appropriate sample, pyrolysis experiment of crude oil and source rocks were selected in this study, hydrocarbon components and carbon isotopic of methane were revealed according to temperature. The parallel first-order reaction model is selected, it is the most widely used chemical kinetic model, and Cramer 3 model is selected by comparing carbon isotopes fractionation models, this model reflects the mechanism of hydrogen isotopic fractionation. The two models were established and calibrated, the fitting effect is good, and the method is feasible.Combining thermal history and embedding history with kinetic models, generation conversion of natural gas and isotope evolution curves obtained in the geological history, basing on the isotopic composition of the natural gas and the geological conditions in the study area,we can study accumulation period and the pool-forming efficiency of natural gas. Geological application results, ① In Leshan-Longnvsi paleo-uplift area, Sichuan Basin, Gaoshiti-Moxi gas filed, crude oil creaking to methane primarily in early-middle Yanshannian and late Indosinian to middle Yanshannian, late hydrocarbon accumulation, the natural gas pool-forming efficiency of Sinian Dengying Formation run up to 83%, Cambrian Longwangmiao Formation about 68%, the reason is that there is two reservoir-caprock assemblages of Sinian, more conducive to oil-gas accumulation, in general, the exploration prospect of this tectonic area is good. Ziyang gas filed, crude oil creaking to methane primarily in Yanshannian, early hydrocarbon accumulation, structural trap is relict paleo-uplift, there is asphaltic sealing, on the one hand, it prevented kerogen-cracking gas from entering the trap, on the other hand, it prevented crude oil-cracking gas from excting the trap, the natural gas pool-forming efficiency of Sinian Dengying Formation is 60%. Weiyuan gas filed, crude oil creaking to methane primarily in Yanshannian, late hydrocarbon accumulation, on the one hand, late origin of structural trap, on the other hand, TSR reaction consume hydrocarbon, the natural gas pool-forming efficiency of Sinian Dengying Formation is 32%. ② Kuqa depression, Kela 2 well, organic matter hydrocarbon generation primarily in Neogene, the natural gas pool-forming efficiency is 79%, late hydrocarbon accumulation. ③ Kelameili gas field, Junggar Basin, organic matter hydrocarbon generation primarily in Yanshannian, the natural gas pool-forming efficiency is 89%, late hydrocarbon accumulation.