Kinetic Modeling of Quartz Cementation and Porosity Loss in Deeply Buried Sandstone Reservoirs
Kinetic Modeling of Quartz Cementation and Porosity Loss in Deeply Buried Sandstone Reservoirs
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DOI：
10.1306/64ed88a4-1724-11d7-8645000102c1865d
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发表时间：
1996-05
期刊：
影响因子：
3.5
通讯作者：
O. Walderhaug
中科院分区：
文献类型：
--
作者：
O. Walderhaug
一个数学上简单的动力学模型模拟了石英胶结和石英砂岩中由此产生的孔隙度损失作为温度历史的函数。溶解的二氧化硅被认为来自于stylolite或含有粘土或云母的单个石英颗粒接触处的石英溶解，并短距离扩散到干净的石英表面上的沉淀点。模拟砂岩体位于柱面岩之间，该体内未发生石英溶蚀或颗粒互渗。石英胶结开始后，压实性孔隙度损失通常较小，因此可以认为模拟砂岩体积内的孔隙度损失等于沉淀石英胶结的体积。石英胶结过程是一个沉淀速率控制的反应，其中单位时间和单位表面积的石英沉淀速率可以用经验确定的温度对数函数来表示。在砂岩温度历史已知的情况下，可以将单位时间和表面积的降水速率表示为时间的函数，将降水速率函数与石英可降水表面积相乘，对时间积分即可计算出一定时间间隔内石英水泥的沉淀量。由于石英水泥的沉淀过程中，石英的表面积会发生变化，所以计算时间较短，每一时间步后对石英的表面积进行调整。石英胶结物在砂岩埋藏史上的总沉淀量p和相应的孔隙度损失，可通过计算各时间步石英胶结物的沉淀增量之和得到。利用该算法可以很容易地模拟出粒度、碎屑石英含量、粘土或其他颗粒涂层丰度、石英前胶结孔隙度和温度历史等参数变化的影响。这种灵活性可以通过计算石英胶结和孔隙度损失的历史来说明，这些砂岩具有一系列的粒度、框架颗粒组成、粘土层发育程度、石英胶结前孔隙度和温度历史。
A mathematically simple kinetic model simulates quartz cementation and the resulting porosity loss in quartzose sandstones as a function of temperature history. Dissolved silica is considered to be sourced from quartz dissolution at stylolites or individual quartz grain contacts containing clay or mica, and diffuses short distances to sites of precipitation on clean quartz surfaces. The modeled sandstone volume is located between stylolites, and no quartz dissolution or grain interpenetration takes place within this volume. After quartz cementation starts, compactional porosity loss is typically minor, and porosity loss within the modeled sandstone volume is therefore considered to be equal to the volume of precipitated quartz cement. The quartz cementation process is mod led as a precipitation rate-controlled reaction where quartz precipitation rate per unit time and surface area can be expressed by an empirically determined logarithmic function of temperature. When the sandstone's temperature history is known, precipitation rate per unit time and surface area can be expressed as a function of time, and the amount of quartz cement precipitated within a certain time interval can be calculated by multiplying the precipitation rate function with the surface area available for quartz precipitation and integrating with respect to time. Because quartz surface area will change as quartz cement precipitation proceeds, the calculations are performed for short time steps, and quartz surface area is adjusted after each time step. The total amount of quartz cement p ecipitated during a sandstone's burial history and the corresponding porosity loss are found by taking the sum of the increments of quartz cement precipitated during each time step. The effect of variation in parameters such as grain size, detrital quartz content, abundance of clay or other grain coatings, prequartz cementation porosities, and temperature history is easily simulated with the presented algorithm. This flexibility is illustrated by presenting calculated histories of quartz cementation and porosity loss for sandstones with a range of grain sizes, framework grain compositions, degree of clay coat development, prequartz cementation porosities, and temperature histories.