摘要:
在目前的粘土矿物转化化学动力学模型中,人们仅考虑了温度、时间和流体介质的影响。然而新近的一些研究表明,超压可以抑制粘土矿物的转化,增加反应活化能。通过超压调节反应活化能,建立超压背景下粘土矿物转化的化学动力学模型,并根据渤海湾盆地板桥凹陷、歧北凹陷超压发育井和歧南凹陷超压不发育井的粘土矿物实测资料,确定了相关参数。模拟结果表明,在超压井中,伊/蒙混层中蒙皂石层含量S%的计算值与实测数据吻合较好,但与Pytter和Reynolds(1989)模型的预测结果相差甚远,在压力系数为1.2~1.7的地层中,超压对S%的抑制最大可达15%~20%。由于在蒙皂石向伊利石转化的过程中,释放出大量S i4+、Ca2+、Mg2+、Fe3+、Na+等阳离子,所以超压对粘土矿物转化的抑制,导致了泥岩中这些阳离子生成量的减少和相邻砂岩中许多胶结作用的延迟,这非常有利于深层(埋深>3 500 m)优质储层的发育和油气藏的形成。
Abstract:
The models are currently applied to model the smectite-to-illite transformation in petroleum basins using time, temperature and the composition of fluids as controlling parameters. However, small number recent studies have indicated that overpressure will retard the clay mineral transformations and enhance the activity energy of kinetic reactions. Using the data collected from both the overpressured wells and the normally pressured wells, a new kinetic model incorporating overpressure was developed, in which overpressure modifies activity energy. The model was tested in the Banqiao Sag, the Qibei Sag and the Qinan Sag of the Bohaiwan basin, China. As the results show that the computed smectite contents S% in I/S mixedlayer are coincident with the measured data, but significantly different from that predicted by Pytter and Reynolds's model(1989), and the smectite contents S% in I/S mixed-layer are retarded by 15%~20% in the overpressure formations with the pressure coefficient of 1.2～1.7. Because lots of such cations as Si4+, Ca2+, Mg2+, Fe3+ and Na+ are yielded in the smectite-to-illite conversion, the retardations of mineral transformations lead to the decrease of the action productions in the mudstones and the postpone of the cementations in the adjacent sandstones, which is propitious to develop high-quality reservoirs and to form hydrocarbon pools in the deep overpressured basin.
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