- 學位論文
Stress-history dependent porosity and permeability in siliciclastic sedimentary rocks - from laboratory tests to in-situ applications
Stress-history dependent porosity and permeability in siliciclastic sedimentary rocks - from laboratory tests to in-situ applications
摘要
地下流體的富集與移棲是現今地球科學重要課題之一，而岩石之孔隙率和滲透率分別為估算儲集層儲量和流體移動速率的重要參數。然而流體流動特性之應力相依性以及其與深度之關係至今仍然有一些爭議。本研究利用高圍壓孔隙滲透儀(YOKO2)進行岩石孔隙率與滲透率之室內量測，並以實驗獲得之壓密曲線嘗試建立應力歷史相依(stress-history dependent)之孔隙率與滲透率之模型。試驗試體來自兩個場址：台灣車籠埔斷層深鑽計畫(Taiwan Chelungpu-fault Drilling Project, TCDP)之深鑽井與二氧化碳封存前導計畫之三鶯一號鑽井(well Sanying-1)，試體之所屬地層主要為台灣西部麓山帶之地層，岩石屬於矽質碎屑沉積岩，地層分別為中新世至更新世之南莊層、桂竹林層、錦水頁與卓蘭層。 本研究主要將分析方向分為五個部分：1. 利用TCDP試體進行室內孔隙率滲透率量測，並建立應力相依之孔隙率滲與透率模型以及應力相依之比儲水係數，實驗結果顯示壓密曲線符合冪次律，經室內實驗加壓解壓後呈現不可回復之變形，進而反映至孔隙率與滲透率隨有效圍壓之變化。2. 利用孔隙率量測結果，並考慮應力歷史對於孔隙率之影響，建立應力歷史相依之孔隙率模型。並利用模型進行線性迴歸獲得每個試體之最大預壓密應力，結果顯示，於TCDP三義斷層上盤之岩層，因侵蝕所造成之釋放應力平均為29.48 MPa，進一步估算TCDP場址三義斷層上盤之抬升量(2482 m)與滑移量(11.5 km)。3. 利用應力歷史相依之孔隙率模型估算TCDP鑽井之孔隙率與深度之關係，與井測孔隙率作比對，結果顯示成功預測應力歷史對孔隙率-深度關係之影響，孔隙率變化趨勢與井測之孔隙率一致，主要受控於有效應力、岩性變化與應力歷史之影響。4. 利用已受抬升作用之三鶯一號井試體與井測資料結合應力歷史相依之孔隙率模型，成功推估未抬升之相對應地層孔隙率與深度之關係，並能推算灌注壓力造成岩石有效應力下降對孔隙率變化之影響。5. 利用TCDP試體，建立應力歷史相依之滲透率模型，估算滲透率與深度之關係。於TCDP鑽井，完整砂岩滲透率為10-12-10-13 m2，完整泥岩滲透率為10-17-10-19 m2。並利用Oda之模型估算裂隙滲透率(10-12-10-15 m2)，估算裂隙滲透率與深度之關係，發現估算岩石滲透率時，泥岩僅需考慮裂隙滲透率，而砂岩則須評估完整岩石對整體滲透率之影響。
並列摘要
The storage and the migration of underground fluid is currently important issue in earth science. Rock permeability and porosity play an important role in determining the reserve of reservoir and the flow rate of fluid. However, the stress dependence of fluid flow properties and the relation between depth and fluid flow properties are controversial. In this study, we use an integrated permeability/porosity measurement system (YOKO2) to measure rock permeability and porosity with different confining pressure in laboratory works. Then, stress-history dependent porosity and permeability can be determined by compaction curves. Tested samples were collected from two sites: the boreholes of Taiwan Chelungpu-fault Drilling Project (TCDP) and well Sanying-1 of preliminary CO2 geological sequestration project. Samples are siliciclastic sedimentary rocks that belongs the formation in Western Foothills including Nanchuang Formation, Kueichulin Formation, Chinshui Shale and Cholan Formation (from Miocene to Pleistocene). In this study, the research direction will be divided into five parts: (1.) We use samples from TCDP to do laboratory measurements and establish stress dependent porosity, permeability and specific storage coefficient. The results show the variation of fluid flow properties with stress follows power law. (2.) We use the porosity compaction curves to build stress-history dependent porosity model through taking the effect of maximum effective stress into account. The average determined maximum effective stress is 29.48 MPa. Moreover, we estimate the amount of uplift (2482 m) and slip (11.5 km) on the hanging wall of Sanyi Fault. (3.) We use stress-history dependent porosity model and propose a method to estimate porosity-depth relationship in TCDP borehole A. The results show the porosity trend is the same in comparison with sonic-derived porosity logging data and we successfully evaluate the effect of stress history. (4.) According to the proposed method of (3.), we evaluate porosity-depth relationship in a deeper and steady burial formation by the samples and logging data from the same and uplifted formation in a shallower borehole (well Sanying-1). At the same time, we determine effect of injection pressure on the porosity variation. (5.) We use the compaction curves to establish the stress-history dependent permeability model, and use this model to estimate the permeability-depth relationship. The permeability of intact sandstone is 10-12-10-13 m2, whereas the permeability of intact mudrock is 10-17-10-19 m2 at the depths of TCDP borehole. On the other hand, we use Oda’s model to estimate the fracture permeability and evaluate the fracture permeability-depth relationship (10-12-10-15 m2). The results show only the fracture permeability should be considered when we estimate mudrock permeability at TCDP site, but the effect of intact sandstone on overall sandstone permeability need to be evaluated.