Chapter 2 Petroleum Geology and Reservoirs

1. Chapter 2 Petroleum Geology and Reservoirs

2. Petroleum Geology (石油地質) Geology (地質) ---研究(1)地球的歷史及構造 (2)記錄在岩石的生物(命)形式 Petroleum Geology(石油地質) ---研究地質以預測石油累積之處所

3. 地球的形成及構造 • 地球的形成 —40～50億年前由宇宙塵(Cosmic dust)的凝結而成 • 地球內部大構造 — • Core--- heavy (4,400 miles) • Mantle--- Lighter (1,800 miles) • Crust--- 10~30 miles

4. 地球內部大構造

5. 在地球上，不管您走到哪裡，你都是在岩石（Rock）的上面。在某些地方，你是站有岩石的上面20哩處在地球上，不管您走到哪裡，你都是在岩石（Rock）的上面。在某些地方，你是站有岩石的上面20哩處 20哩是多少? 6MILES = 9.6 KILOMETERS 20MILES = 32 KILOMETERS 喜馬拉雅山大約有6哩高 所以20哩是喜馬拉雅山的3倍高，其間有很多的岩石。

6. 地球表面的變化 -- Rock cycle 噴出 形成 Primeval(初期的) Atmosphere(大氣) 地球內部 Water vapor and gases Magma (岩漿) 地殼冷卻 heat 地殼收縮變形而皺摺 Metamorphic rocks Igneous rocks (火成岩) erosion 下雨 heat pressure erosion erosion Sedimentary rocks Sediments (沉積物) pressure cementation

7. Prorsity Permeability Reservoir Rock Sandstones (SiO2) Carbonates Limestones (CaCO3) Dolomites (CaCO3, MgCO3) Reservoir Rock

8. 沉積岩的分類

9. 地球的歷史 • 寒武紀(Cambrian)【約5.5億年前】開始在海洋裡有大量的生物(生命) 在寒武紀之前為前寒武紀(Precambrian) • 地質年代自寒武紀開始 > 地質代年表(Geologic Time Scale) • 泥盆紀(Devonian)時期【約3.3億年前】陸上有大量植物及動物

10. Geological Time Scale

11. 地層年代表

13. Petroleum accumulation(石油累積) • Petroleum accumulation(石油累積)必須具備 (1)Oil ＆ gas 之來源 (2)具有孔隙(porosity)及滲透率(permeability)之Reservoir Rock (3) 要有trap(封閉)以阻擋流體的流動

14. 石油的來源

15. 含石油的岩石都是由很小顆粒的砂、淤泥或泥土開始的，就如同地上的土壤含石油的岩石都是由很小顆粒的砂、淤泥或泥土開始的，就如同地上的土壤 ， 經過多年的風吹雨打，這些土壤流到低窪處而停下來。 通常，這些低窪處是水底、河底、湖底或海底。

16. 砂、淤泥，泥土的顆粒沉到水裡，蓋在死的矽藻類以及其他的動植物之上。而且，水被夾在這些砂、淤泥及泥土的顆粒之中。砂、淤泥，泥土的顆粒沉到水裡，蓋在死的矽藻類以及其他的動植物之上。而且，水被夾在這些砂、淤泥及泥土的顆粒之中。 不久，這些顆粒，又被其他的動植物殘骸覆蓋。這個過程，一再的重複，最後，泥、砂及水累積達幾千呎厚。 這些砂、泥在堆積過程中，底部的砂、泥受到上部砂、泥而擠壓 在河流、湖及海底的泥、砂、水及動植物殘骸所受的覆蓋壓力逐漸的變大 當覆蓋深度加大越深，其溫度也增加。經過幾百萬年之後，在適當的壓力及溫度之下，這些泥砂顆粒就變硬而變成岩石，類似褐色或灰色的水泥。 當動植物的殘骸腐朽之後，形成石油及天然氣，大部分的石油及天然氣係由相當微小的動植物殘骸而來的 確認的石油及天然氣之形成原因仍不清楚。但是，溫度、壓力及細菌是很重要的因素。

17. 石油的來源 • －石油來自沈積岩的有機物質 • －海洋裡大量的生物不停的，緩慢的掉落到海底。 雖然在掉落的過程中，有部分被吃掉或被氧化掉， 但另部份(動物或植物)掉落海底而埋在沼澤或泥濘之 海底 • －海底繼續被Sand(砂)，Clay(黏土)及debris等沈積物埋沒 一直到幾千英呎 • －沈積物的壓力開始作用。 • 細菌由殘餘的有機物質中，用掉氧而分解物質， 使其僅存碳及氫 • －在高度的壓力及重量的地層影響之下， Clays變成Shales → 石油產生

18. Petroleum formation requires that organic source clays become mature by subjection to pressure and temperature.

19. 石油形成的重要條件 • 225℉ < temperature < 350℉ 有利條件 • temperature < 150℉ 不可能形成石油 • temperature > 500℉ 有機物質碳化， 不能形成石油

20. Generation of gas and oil

22. In geology and oceanography, diagenesis is any chemical, physical, or biological change undergone by a sediment after its initial deposition and during and after its lithification, exclusive of surface alteration (weathering) and metamorphism.

23. Catagenesis can refer to: • Catagenesis (geology)– The cracking process in which organic kerogens are broken down into hydrocarbons; • Catagenesis (biology)– Retrogressive evolution, as contrasted with anagenesis.

24. Metamorphism can be defined as the solid state recrystallisation of pre-existing rocks due to changes in heat and/or pressure and/or introduction of fluids i.e without melting. There will be mineralogical, chemical and crystallographic changes

25. Prolonged exposure to high temperatures, or shorter exposure to very high temperatures, may lead progressively to the generation of hydrocarbon mixtures characterized as condensates, wet gases and gas. • The average organic content of potential source rocks is about 1% by weight. The Kimmeridge clay, the principal source rock for North Sea oil average about 5% carbon (~7% organic mater) with local rich streaks greater than 40%. The hydrogen content of the organic matter should be greater than 7% by weight for potential as an oil source.

26. It is a rule of thumb that for each percentage point of organic carbon in mature source rocks, some 1300~1500 cubic meters of oil per km2-m (or 10~40 barrels of oil per acre-ft; or 56-225 ft3/ 43560 ft3) of sediment could be generated. It is not, however, necessarily true that all the oil generated will be expelled or trapped in porous rock.

27. 經過porous bed 有permeability 石油形成後 Migration Traps＆Reservoir Rocks 由於Compaction of Source bed 石油移棲 • The migration process involves two main stages, namely from the source rock and then through a permeable system.

28. Migration of petroleum -- from the source rock

29. 當石油形成後，它們並不會停留在原地，就如同您我一樣，會搬遷及旅遊當石油形成後，它們並不會停留在原地，就如同您我一樣，會搬遷及旅遊 它們到哪裡去?

30. 它們向上移動，有時候通過地球的斷裂地層（稱為斷層，Faults）它們向上移動，有時候通過地球的斷裂地層（稱為斷層，Faults） 沿著斷層而到達地面的石油及天然氣稱為滲流（Seep），在加州有幾百處的滲流，大都是在油、氣田的附近 Jack，你剛才所踩到的是自然滲流

31. 印地安人及其拓荒者，利用滲出的石油做很多用途：例如，籃子的防水，馬車的潤滑等。印地安人及其拓荒者，利用滲出的石油做很多用途：例如，籃子的防水，馬車的潤滑等。

32. 大部分的石油及天然氣在到達地表之前遇到無滲透率的的岩層（稱為蓋岩，Cap Rock）或其他的障礙層，而陷在地層裡。 當很多的石油積集在蓋岩（Cap Rock）或其他障礙物下的地層時，就形成了儲石油及天然氣層（Oil and Gas Reservoirs） 典型的儲石油及天然氣層（Oil and Gas Reservoirs）是在砂粒層，稱為砂岩（Sandstone），石油、天然氣及水是夾在砂粒與砂粒間的小空間裏，而不是在一個很大而寬廣之池塘。

33. Migration of petroleum -- from the source rock ** Capillary effect ** Microfractures Since the generation of petroleum is accompanied by volume changes which can lead to high local pressures, there may well be an initiation of microfractures which provide an escape route into permeable systems such as sedimentary rocks or fault planes. The source rock microfractures are believed to heal as pressures are dissipated.

34. Migration of petroleum --through a permeable system ** Fluid potential gradient or gravity effect In the permeable system the transport occurs under conditions of a fluid potential gradient which may take the hydrocarbon to surface or to some place where it becomes trapped. It might be assumed that less than 10% of petroleum generated in source rocks is both expelled and trapped, as shown in the example of Fig. 2.5.

36. Petroleum traps(石油封閉) • The characteristic forms of petroleum trap are known as structural traps(構造封閉) and stratigraphic traps(地層封閉), with the great majority of known accumulation being in the former style.

37. Erosion － Sedimentation Uplift － wearing down Strata or bed Unconformity －disconformity －Angular unconformity Upward downward Upper crust move Arches (or upfold) → anticlines Traughs (or downfold) → synclines Fault Folds Normal Reverse Thrust Lateral Important to petroleum accumulation 地質構造（Geological Structures）

38. 造山運動之應力所造成 沉積過程所造成 Figure 1.13. Basic hydrocarbon reservoirs are structural and / or stratigraphic traps. Figure 1.12. Two general kinds of unconformities are disconformity (A) and angular unconformities (B) and (C).

39. Structural traps－an arched upper surface Stratigraphic traps---up-dip termination of porosity (permeability) 封閉(traps) Anticline trap Fault trap Dome and plug trap Structural traps Disconformity Angular unconformity Unconformity traps Lenticular trap Stratigraphic traps 封閉(traps) Combination traps

40. Cap rock • Impermeable rocks provide seal above and below the permeable reservoir rocks. At equilibrium conditions, the density differences between the oil, gas and water phases can result in boundary regions between them known as fluid contacts, i.e. gas-oil and oil-water contacts.

41. Structural trapa(構造封閉) -- Anticline Longitudinal view of a typical anticline. The oil cannot escape upward because of the impervious shale bed above the oil sand; neither can it travel downward because of the water that is associated with an accumulation of this type. Anticlines－ Of the many types of structural features present in the upper layers of the earths crust that can trap oil, the most important is the anticlines－the type of structure from which the greater part of the word’s oil has been produced. Anticlines are upfolds of beds in the earth’s crust, and, when the proper conditions are present, oil accumulates within the closure of there folds.

42. Structural trap-- Anticline Plan view of a typical anticline, showing locations of longitudinal view A-B and lateral view C-D. Lateral, or end view, of a typical anticline.

43. Structural traps Figure 1.7. Schematic cross section shows deformation of earth’s crust by bucking of layers into folds Figure 1.8. Simple kinds of folds are symmetrical anticline (A), plunging asymmetrical anticline (B), plunging syncline (C), and dome with deep salt core (D). Figure 1.9. Simplified diagram of the Milano, Texas, fault.

44. Structural traps– dome & anticline Figure 1.15. Oil accumulates in a dome-shaped structure (A) and an anticlinal type of fold structure (B). An anticline is generally long and narrow while the dome is circular in outline. (Courtesy of American Petroleum Institute)

46. Structural traps -- faults Figure 1.10. Simple kinds of faults are normal (A), reverse (B), thrust (C), and lateral (D). Figure 1.11. Variations of normal and reverse faulting are rotational faults (A) and upthrust faults (B).

47. Structural traps Figure 1.14. Common types of structural traps

48. Structural trap – fault & anticline Figure 1.16. Gas and oil are trapped in a fault trap-a reservoir resulting from normal faulting or offsetting of strata. The block on the right has moved up from the block on the left, moving impervious shawl opposite the hydrocarbon-bearing formation. (Courtesy of American Petroleum Institute) Figure 1.17. Shown in map view, fault traps may be simple (A) or compound (B).

49. Stratigraphic traps(地層封閉)

50. 造山運動之應力所造成 沉積過程所造成 Figure 1.13. Basic hydrocarbon reservoirs are structural and / or stratigraphic traps. Figure 1.12. Two general kinds of unconformities are disconformity (A) and angular unconformities (B) and (C).