| 摘要: | 對於盆地構造發育、石油蘊藏與開採以及發展中的二氧化碳封存評估等，了解沉積盆地滲透率分布為一項相當基本的工作。另一方面，岩石的孔隙率也很重要，以二氧化碳封存為例，為了解地層可容納多少的二氧化碳，即需要地層之孔隙率方得以計算。相對於滲透率的量測，岩石的孔隙率量測較方便，因此許多的研究嘗試建立孔隙率及滲透率間的關係，並間接根據岩石孔隙率資料來推測岩石的滲透率。 本研究利用高圍壓滲透/孔隙儀(YOKO2)以量測岩石試體在受應力作 用下的孔隙率和滲透率的變化情形，試體取自中油深井(深度約1~2 公里)與北投貴子坑地表露頭。根據本試驗結果及文獻資料，本研究發現砂岩與粉砂岩、頁岩的孔隙率、滲透率實驗結果明顯不同，砂岩孔隙率(12%~20%)與滲透率(10-13m2~10-16m2)較大，而粉砂岩與頁岩孔隙率(7%~11%)與滲透率值(10-15m2~10-19m2)較小。大致上同一岩性之岩石其孔隙率隨地質年代增加而遞減，由大至小排列分別為卓蘭層、桂竹林層、南莊層、五指山層。氣體滲透率實驗的量測應考慮克林堡效應，經克林堡效應修正後發現，砂岩試體之氣體與液體滲透率差異不大，然而粉砂岩或頁岩之液體滲透率將較氣體滲透率低了1~2 數量級，使用氣體進行粉砂岩或頁岩的滲透率量測可能高估了液體之滲透率。 孔隙率與滲透率的應力模型建立，應考慮最大預壓密應力，以合理的與實驗資料擬合。本研究分別以滲透率-應力曲線及孔隙率-應力曲線決定岩石所受最大預壓密應力，結果發現孔隙率-應力曲線之正常壓密及過壓密轉折點所對應之有效應力，與試體之最大預壓密應力相當接近，亦最大預壓密應力可透過孔隙率試驗合理推估。 根據本研究建議之應力歷史相依之孔隙率及滲透率力學模式，將各試體相同圍壓下之孔隙率與滲透率於雙對數座標下作圖， 並與Kozeny-Carman 方程式所得到的孔隙率對滲透率的關係曲線進行比較，發現考慮最大預壓密應力所得之孔隙率與滲透率關係曲線並不如Kozeny-Carman 方程式一樣是單一曲線關係，亦即應力歷史將影響岩石之孔隙率與滲透率關係式。 To study the generation of basin structure, oil mine, oil extraction, and the developing technology of sealing for safekeeping of CO2, etc., understanding the spread of permeability of sedimentary basin is a fundamental job. Additionally, the porosity of rocks is important as well, take the sealing and safekeeping of CO2 for instance, it is necessary to know the porosity of rock before we can get to know how much amount of CO2 can be stored in the layer. Relative to the measurement of permeability, the measure porosity of rocks is easier, therefore, many studies try to develop the relationship between permeability and porosity of rocks, and estimate the permeability indirectly from porosity of the rocks. This study uses YOKO2 to measure the porosity and the permeability of rocks under by stress. The sample is obtained from the deep well of CPC (around 1~2km of depth), and from the ground surface of Kwetsuken of Beto. According to this study, we find the permeability and the porosity of rocks among sandstone, siltstone(or shale) are quite different, the porosity of sandstone (12%~20%) and its permeability (10-13m2~10-16m2) are larger, whereas the ones (7%~11%) & (10-15m2~10-19m2) of siltstone(or shale) are smaller. Basically, the porosity of sandstone decrease as the buried depth increase. From the elder to the younger, Cholan formation have the largest porosity, Kueichoulin formation the next, then Nanchung formation, Wuchishan formation have the smallest porosity. The measuring permeability by gas flow should take the Klinkenberg effect into account. After the modification of Klinkenberg effect on permeability, we find the tiny difference between permeability by gas flow and liquid flow, however, permeability of siltstone( or shale) using liquid flow are 1~2 orders samller than permeability using gas flow. It may overestimate the permeability of siltstone(or shale) using gas flow to measure permeability. The relation between stress and the porosity/permeability model of rocks should take the maximum pre-consolidation stress into account, so as to model the experiment data reasonably. This study determines the maximum preconsolidation stress from the permeability-stress curve and porosity-stress curve, respectively; as a result, we find the corresponding effective stresses to the turning points of the normal consolidation and over-consolidation levels of porosity-stress curve are very close to the one estimated from the buried depth of sample, i.e. the maximum pre-consolidation pressure can be estimated reasonably through the porosity-stress curves. According to the stress-history-dependent models of between porosity and permeability, this study proposed a stress-history dependent relation between porosity and permeability. A stress-history dependent relation is fuction of the maximum pre-consolidation stress find the relative between porosity and permeability instead of the single curve as the equation of Kozeny-Carman exhibits. That is, the stress history will influence the relation between the porosity and the permeability. |
