摘要
在某些著作中，计算上覆岩层压力（ｐ０）的一个公式为：ｐ０＝σ＋ｐｐ（其中，σ为骨架颗粒压力，又称基岩应力；ｐｐ为地层压力，即孔隙流体压力）。从力学基本定义出发，证明原来对地层压力、上覆岩层压力和颗粒压力的定义有不正确处，从而证明这一公式是错误的。分析了地层孔隙流体和岩石骨架颗粒在正常情况下所受的应力情况，给出了简单条件下的应力张量形式。用圆柱形毛细管描述孔隙，提出地层面（将地层岩石视为多孔介质时岩石颗粒的密置层面）的概念，认为流体在地层面遇到孔隙时，将沿毛细管的上部绕过。据此，将上覆岩层压力的定义修正为：“埋藏在一定深度的沉积物，单位地层面面积所承受的上覆全部沉积物的重力”；将颗粒压力定义改为：“地下某一深度的地层面上的颗粒压力，指该点以上至地面岩石的总重力与由地层压力对该点产生的作用力之差施加于该点的压力。”新定义既符合地下情况，又避免与已知基本原理矛盾。利用颗粒压力新定义，很容易得出：σ＝ｐ０＋φ０ｐｐ；根据力的平衡原理，同样可得新公式：ｐ０＝σ′＋φ０ｐｐ（其中，σ′为支撑应力，φ０为地下某深度点的孔隙度）。
he author of the article puts forward his objection to the correctness of a formula
on overburden pressure (p0=+pp), and raises a new formula (p0='+0pp). From the definition of
formation pressure and the original definitions of overburden pressure and graintograin
pressure, and by using the relevant essential theory and concepts well known, the author has
proved that the formula (p0=+pp) and its explications are erroneous. In approach to the formula,
a new concept about formation surface is narrated by the author. By formation surface we mean
closely arranged layer surfaces of rock grains, when formation rock is looked as porous. The
pore is described with the cylindrical capillary. When the fluid on closely arranged layer
surfaces encounter the pores, it will bypass the top of the capillary. Based on this, the new
definitions about overburden pressure and graintograin pressure are raised. From the
abovedefinitions, the word formation surface is only added in a suitable position of the original
definition. The later become: Graintograin pressure in some deep formation surface refers to
that the pressure is exerted on the point by the difference between total gravity of rock from the
point to the surface and the force produced on the point by formation pressure. The new
definitions not only tally with the underground actual situation, but also avoid the contradiction
to known fundamentals. A formula = p00pp is easily obtained by the new definition of
graintograin pressure. The formula p0='+0pp may be obtained according to balance principle of
force.
出处
《石油勘探与开发》
SCIE
EI
CAS
CSCD
北大核心
1999年第3期99-103,共5页
Petroleum Exploration and Development
关键词
上覆岩层
压力计算
计算公式
钻井
井壁失稳
Formation pressure, Gravity, Stress, Rock grain, Rock pore, Definition,
Calculation, Equation
