沉积地层埋藏过程对泥岩压实作用的影响

同一岩层经过不同的埋藏轨迹最终达到相同的埋藏终止状态,其孔隙度的保存量存在差异。文中从粘弹塑性体应力-应变模型(Bingham模型)出发,经过严格的数学推导,得出变速埋藏条件下地层孔隙度与埋深和经历时间的函数关系,认为地层孔隙度受埋藏时间和埋藏深度两个因素共同影响,其实质是孔隙度大小受地层埋藏史控制。为了充分证实这一结论,从数学上推导四大类型(加速型、恒速型、减速型和先埋后停型)沉降盆地孔隙度的时间深度函数。研究表明,加速型埋藏盆地对孔隙的保存最为有利,减速型埋藏盆地对孔隙的保存最为不利,恒速型埋藏盆地对孔隙的保存居中。该结论不仅在中国南海北部湾盆地和珠江口盆地得到很好的验证,而且与前人通过统计3种类型埋藏盆地相对应的3个代表性沉积盆地(前陆盆地、裂谷盆地和克拉通盆地)孔隙度的演化关系相一致。

The influence of burial history on mudstone compaction

The same stratum may reach the same embedding ending state through different burial traces. However,the preservation of porosity varies with each other,which highlights the influence of burial history. Based on the viscous-elastic-plastic stress strain model(Bingham model),we have rigorously deduced the functional relationship of porosity with burial depth and time. The essence of the porosity depending on burial depth and time is that the burial history of the stratum controls the variation degree of porosity. In order to fully testify this conclusion,we deduced the porosity function of burial time and depth for the four general types of subsiding basins,i.e.,the accelerating,the constant speed,the decelerating and the early burial then standing-still type of basin. By comparison,it is concluded that the accelerating burial basin is the most favorable for the preservation of porosity,the decelerating burial basin is the worst for porosity preservation,and the constant speed burial basin is in the middle. This principle not only has been confirmed by the Beibuwan Basin and Zhujiangkou Basin in China,but also is statistically concordant with the porosity development in foreland basin,rift basin and craton basin that represent the three general types of basins mentioned above respectively.