为什么我们分开考虑静水压力和地面压力吗?- 江南体育网页版- - - - -地球科学堆江南电子竞技平台栈交换 最近30从www.hoelymoley.com 2023 - 07 - 10 - t21:21:46z //www.hoelymoley.com/feeds/question/15427 https://creativecommons.org/licenses/by-sa/4.0/rdf //www.hoelymoley.com/q/15427 3 为什么我们分开考虑静水压力和地面压力吗? 宝石 //www.hoelymoley.com/users/14137 2018 - 10 - 25 - t00:15:24z 2021 - 07 - 09 - t00:10:34z < p >在石油地质学,为什么我们分开考虑静水压力和地面压力吗?肯定在任何时候的压力,是否液体或岩石,在深度是相等的重量流体和岩石覆盖它吗?因此为什么不是液体和固体的压力等于在一个特定的深度?< / p > //www.hoelymoley.com/questions/15427/-/15519 # 15519 2 由埃里克回答为什么我们分开考虑静水压力和地面压力吗? 埃里克 //www.hoelymoley.com/users/12155 2018 - 11 - 07 - t12:04:11z 2018 - 11 - 07 - t13:49:45z < p >我认为(但我不是一个专家主题),你的假设是错了!< em >孔隙流体压力< / em >和< em >有效压力对岩石< / em >并不相同。在测井测量,它只是衡量的孔隙流体压力,< span class = " math-container " > $ \ sigma_ \文本{孔隙}={水}\ rho_ \文本广州$ < / span >。只要水是通过毛孔连接到地球表面,它被认为是静水(没有),毛孔将创建一个测量压力的压力只推覆水,携带上覆岩石的岩石会照顾自己!如果你钻钻孔,水列将地球表面完全注满水。整个系统的有效压力然后< span class = " math-container " > ${有效}= \ \ sigma_ \文本sigma_ \{地面}-文本\ sigma_ \{孔隙}$ < / span >文本。< / p >

However, once a seal is formed (e.g., a shale formation overlies a formation), the pore water suddenly has to also carry the overlying rock formation! The pressure will then increase significantly, and the pore water pressure that you measure becomes more similar to the effective pressure.

The pore water pressure thus increased below a seal because it is stuck. Once you drill a hole from the surface to this formation, you allow water to flow freely to the surface, and it is clear that it is under overpressure with respect to the lithostatic pressure, because it will blow out!

See also this comprehensive set of slides: http://ocw.utm.my/pluginfile.php/1509/mod_resource/content/0/To_upload_OCW_Formation_pressures.pdf .

//www.hoelymoley.com/questions/15427/-/22512 # 22512 1 答案由h . h .为什么我们分开考虑静水压力和地面压力吗? H . H。 //www.hoelymoley.com/users/22960 2021 - 07 - 08 - t21:52:20z 2021 - 07 - 09 - t00:10:34z < p >我花了一段时间才得到它(和我不是一个地质学家或石油工程师或任何东西,只是有人谁知道基本的物理学和已读地质教材),但我想我明白了埃里克的回答是:它是基于浮力。< / p > < p >考虑列透水岩石和土壤的曝气带饱和带。(我要讲水,但是它也适用于油或空气或其他流体密度小于当地的岩石或土壤)。如果任何重量从土壤/摇滚推饱和带的水,它就会把水的方式,提高水位,同时降低一些岩石和土壤。这是由于岩石和土壤的密度比水,所以重力势能减小当岩石/土壤和推动同等体积的水。< / p >

Water with an impermeable layer above it can support some of the weight of the rock because the buoyancy force this would create can't push the water up through the impermeable layer. If a hole were made in said impermeable layer, displaced water could move up through that hole to allow the supported rock to settle a little lower (which is how artesian wells work).


If the water is supporting some of the weight of the rock, this fraction of that weight (this fraction of the lithostatic pressure) will have to be supported by pressure that is locally (approximately) hydrostatic (equal in all directions), because that's the only way stationary fluids can exert pressure. This means the water pressure can also push sideways, which seems like it should matter when strata are tilted or curved so that part of the permeable bed is open to the surface while the rest is overlied by an impermeable bed, as in a typical aquifer, and it does:

As you move sideways (on a surface of constant gravitational potential(pot. energy÷mass)/geopotential) the hydrostatic pressure in the water must be stay constant; otherwise, the water would flow sideways to equalize it. (Actually, this isn't entirely true, as can be determined from my geology textbook, which notes that "pores ... provide resistance to flow", related to permeability of the rock/soil and viscosity of the fluid I guess, and that "pressure is lost through fractures (leaks)", presumably in the "imperable" layers, but it's a good starting approximation.) As you move down through the water, the pressure goes up according to how much more weight (weight of the water and possibly a bit of the rock) the water at that point needs to support. (Reverse as you go up.)

Now, remember that the water at the top of the water table in the area with a zone of aeration above it, and atmosphere above that, cannot support any lithostatic pressure. As you go straight down from here, let's assume only the weight of the water above being supported by the water, not any rock/soil. (I think that's true, but I'm not sure. In any case, it doesn't significantly affect my point if not.) As you move sideways from a point below the permable zone of aeration to a point below an impermable bed, the height of water above you has to drop from the height of the water table to the height of the bottom of the impermable bed (whenever this gets lower than the water table under air). More importantly, this generally means there is less weight of (contiguous) water pushing down on the water where you are. (I'm just noticing that, since much or most of the volume underground is rock/soil, volume and therefore weight of water in a column is only proportional to height in rock/soil of constant porosity, but that approximation basically works within a single permable bed.) However, the hydrostatic pressure must stay (approximately) the same. The only way to accomplish this is for the water to push up some of the rock and support enough of the lithostatic pressure to (approximately) equal the weight of water lost. (Actually resistance to flow and leaks mean the pressure goes slightly down as you move further sideways away from an area below air, which is why the "artesian-pressure surface"/"potentiometric surface" above an aquifer slopes down as you move away from the "recharge area" rather than being flat.)


I imagine a little extra complexity is added when your dealing with gasses rather than liquids (so the density of the fluid is highly dependent on the hydrostatic pressure it's under), when fluids are in motion rather than stationary, or when you consider the permeability of rocks quantitatively rather than as just "permeable" and "impermeable".

Baidu
map