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在储层中,随着埋藏深度的增加,温度上升,石油转化成热解气。在裂解过程中,根据氢的平衡条件,每桶石油将产生大约3 000ft~3(85m~3)(标准温度和大气压条件下)的气,另外析出一些石墨残渣。如果将石油、热解气和石墨残渣之间的体积关系,同气体在孔隙水中的溶解能力的数据,以及气体非理想性参数(Z系数)结合起来,那么对任何程度热裂解所产生的压力均可以计算。计算结果表明,在有效隔绝的系统中,压力会升得很高,很可能显著超过岩石的承受力,使岩层发生破裂,从而引起压力释放和气体散失。大约只要有1%的石油裂解就能达到岩静压力梯度(1.0psi/ft或22.6kPa/m)。如果最初石油充满开放系统(即处在静水压力条件下)的油藏,然后这些油热裂解成气,则会有大约75%的热解气失掉,或者油藏的实际容积相应的增大,例如通过气、水界面下移使体积增大。
In reservoirs, as burial depth increases, the temperature rises and the oil turns into pyrolysis gas. In the cracking process, depending on the equilibrium conditions of the hydrogen, a barrel of oil will generate about 3 000 ft 3 (85 m 3) of gas (at standard temperature and atmospheric pressure) and will precipitate some graphite residue. If the volumetric relationship between petroleum, pyrolytic gas and graphite residue, data on the gas dissolving ability in pore water, and gas non-ideality parameters (Z-factor) are combined, the pressure generated by any degree of pyrolysis Can be calculated. The results show that in an effectively isolated system, the pressure rises very high and is likely to significantly exceed the bearing capacity of the rock, causing the formation to rupture, causing pressure release and gas loss. The rock static pressure gradient (1.0 psi / ft or 22.6 kPa / m) can be achieved with about 1% oil cracking. If the initial oil was filled with an open system (ie under hydrostatic pressure) and then the oil cracked into gas, about 75% of the pyrolysis gas would be lost or the actual volume of the reservoir would correspondingly increase, For example by gas, water interface down to make the volume increase.