开发地质培训英文教材

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1、Production GeologyTable of Contents1. Introduction2. Non-marine clastic depositional systemsa. Introductionb. Low sinuosity fluvialc. High sinuosity fluviald. Eoliane. Alluvial fan3. Shallow and deep marine systemsa. Deltasb. Shore-zonec. Deep marine4. Sequence Stratigraphya. Introductionb. Fundamen

2、tal concepts and terminologyc. Systems tractsd. Application5. Reservoir Geophysicsa. Introductionb. Terminology and fundamental conceptsc. Seismic acquisitiond. Seismic processinge. Seismic framework interpretationf. Acoustic impedance, attribute analysis, direct hydrocarbon indicators, and 4D seism

3、ic6. Fractured Reservoirsa. Introductionb. Key conceptsc. Types of fracturesd. Character of the fracture planee. Detecting and quantifying fracturesf. Fracture porosity, permeability, and productivityg. Data gathering and reservoir characterization7. Capillary Pressurea. Introductionb. Buoyancy and

4、capillary forcesc. The capillary pressure equationd. Determining capillary pressuree. Displacement pressure and saturation distributionsf. The Leverett J-functiong. Reservoir sealsh. Hydrostatic versus hydrodynamic reservoirsi. Examples of how capillary pressure controls the location of oil-water co

5、ntacts8. Reservoir Heterogeneities and the Use of Geostatisticsa. Introductionb. Types of heterogeneitiesc. Steps to identify heterogeneitiesd. Importance of capturing the appropriate heterogeneitiese. Why geostatistics is neededf. How to calculate a variogramg. Variogram modelingh. Kriging versus c

6、onditional simulationi. Object modelingj. Sequential Gaussian simulation9. Geocellular Modelinga. Introductionb. Project scopingc. Data import and quality checkingd. Framework constructione. Three-dimensional griddingf. Property modelingg. Volumetrics and net payh. Realization assessmenti. Upscaling

7、 and exportj. Numerical simulation and reserves 1. IntroductionProduction geology is a geological sub-discipline that focuses on identifying and producing hydrocarbons from known accumulations. The responsibilities of the production geologist are to 1) determine development well locations that targe

8、t remaining hydrocarbons, 2) help explain the performance of existing wells by understanding the reservoir quality and lateral continuity of producing horizons, 3) determine the volume of hydrocarbons-in-place and the uncertainties associated with this value, and 4) look for additional opportunities

9、 including missed pay behind pipe in existing wells, shallower and deeper pay, and step-out wells that expand the existing field or discover new fields. The primary objective of this course is to provide participants with insights and tools to help them become an effective production geologist. Prod

10、uction geologists differ from exploration geologists, who often work with little data and generate broad play concepts that are sharpened into prospects. The production geologist typically has more data, generates more detailed descriptions, and must be prepared to answer many specific questions tha

11、t exploration geologists do not consider. A comprehensive list of these questions is included in Table 1-1. While this class will not address all of these questions, it will provide participants with fundamental skills and a philosophy of how to conduct their work, so that the goal of answering all

12、of these questions can be reached. A secondary objective of this course is to help participants understand how to build geocellular models, including how to incorporate information from other disciplines, and how long it should take to build these models. Figure 1-1 is generic geocellular modeling w

13、orkflow, showing different tasks and how they inter-relate. Although this workflow must be modified for each individual project, it nonetheless provides a basic template for carrying-out geocellular modeling work. Geocellular models have become the primary tool used by geologists to capture their da

14、ta and interpretations. These models also contain information provided by petrophysicists, geophysicists, and reservoir engineers. The models are used for development planning, reservoir visualization, and geosteering wells. In order to construct these models, geologists must be experts in many crit

15、ical areas including the six listed below: Depositional systems: to understand the likely geometry, lateral continuity and reservoir quality of sandbodies in the reservoir Sequence stratigraphy: to understand the nature of key surfaces, how they should be correlated through the reservoir, and their

16、role as baffles and barriers to fluid flow Reservoir geophysics: to determine reservoir structure, faulting, and variations in properties in interwell areas Geostatistics: to use appropriate stochastic techniques for distributing petrophysical parameters including facies types, porosity, and permeab

17、ility Capillary pressure: to distribute water saturation in the model and relate this to variations in rock quality Geocellular modeling: to understand the techniques and workflows used to build models, and how the results are used by reservoir engineers and othersThis course focuses on these six ar

18、eas, explaining the fundamentals concepts of each and illustrating these concepts with diagrams, photographs, and exercises.2. Non-Marine Clastic Depositional Systems2a. Introduction. Non-marine clastic depositional systems include low-sinuosity fluvial, high-sinuosity fluvial, eolian, and alluvial

19、fan depositional environments (Figure 2a-1). High sinuosity fluvial systems make excellent reservoirs due to their high net-to-gross ratios, coarse grain size, and sheet-like distribution. Low-sinuosity fluvial systems often have lower net-to-gross ratios than high-sinuosity systems and sandbodies o

20、f limited size and lateral extent. Eolian reservoirs are excellent reservoirs because of their clean, well-sorted nature. In contrast, alluvial fan reservoirs are relatively rare due to extreme variations in grain size, sorting, and clay content.This chapter explains how sands and shales in each of

21、these environments are deposited and preserved, and how to recognize them from cores and logs. It also discusses the size, shape, and continuity of different sandbody types, and the key heterogeneities contained within them that impact reservoir fluid flow.2b. Low-sinuosity Fluvial Systems. A low-si

22、nuosity fluvial system is a deposit of sand and gravel, generally with lesser amounts of silt and mud, produced by a series of low to moderately sinuous braided rivers traversing a coastal plain. It differs from a high-sinuosity system in that there are multiple river channels, and it differs from a

23、n anastamosing system in that there are no permanent islands between the river channels (Figure 2b-1).Sand and gravel deposited in this fluvial system are concentrated in bars including longitudinal, lateral, and transverse bars (Figure 2b-2). Longitudinal bars have their long axis oriented parallel

24、 to flow whereas transverse bars are oriented transverse to the flow direction and migrate downstream. Lateral bars form along the channel margins and are submerged during flood events when coarse material is deposited on their surface. In addition to these basic types of bars, many others have been

25、 recognized and classified (Figure 2b-3). These bars are not stable, but instead migrate, and can be destroyed or enlarged with time (Figure 2b-4). The upstream portions of the bars accumulate coarser-grained sand and gravel with a blocky log signature whereas the downstream portions accumulate fine

26、r-grained sand and silt with a fining-upward log signature (Figure 2b-5).Low-sinuosity fluvial systems are composed primarily of massive-appearing, sheet-like or tabular sandstone bodies of relatively high lateral continuity. These are separated by discontinuous silty sandstone intervals or less com

27、monly by thin and discontinuous shales. The most common classes of shales are floodplain shales, channel-fill shales, and thin shales that drape various bars. The most important of these are floodplain shales which can extend laterally for hundreds of meters. The major control on shale continuity is

28、 their subsequent erosion by fluvial processes, resulting in laterally discontinuous permeability baffles instead of permeability barriers. Typical reservoir characteristics of low-sinuosity fluvial systems are summarized in Table 2b-1.A significant portion of the worlds oil reserves are contained w

29、ithin low-sinuosity fluvial sandstone reservoirs. It is estimated that there are at least 30 billion stock tank barrels of remaining proven oil reserves and 40 trillion cubic feet of remaining proven gas reserves. An excellent example of one of these reservoirs is the Prudhoe Bay field on the North

30、Slope of Alaska, which is the largest oilfield in North America (Figure 2b-6). It has 12 billion barrels of recoverable oil reserves and a gas cap containing 47 trillion cubic feet of gas. The lower part of the reservoir contains heterogeneous delta-front and lower delta-plain sandstones whereas the

31、 upper part consists of more homogeneous low-sinuosity fluvial sandstones and conglomerates interbedded with floodplain, abandoned channel, and drape shales. An important heterogeneity in addition to shales in this reservoir is open-framework conglomerates. These were deposited as laterally extensiv

32、e gravel bars and now serve as “thief” zones which receive most of the injected water or gas during secondary recovery operations.2c. High-sinuosity Fluvial Systems. A high-sinuosity fluvial system is one in which the ratio of the channel length to the down-valley distance exceeds 1.5. Higher sinuos

33、ity is favored by relatively low slopes, a high ratio of suspended to bed load sediment, cohesive bank material, and relatively steady discharge. The lateral distance across the active river channel system is referred to as the channel belt width, and the channel belt itself is contained within a la

34、rger floodplain (Figure 2c-1). With time, the channel belt migrates across the floodplain, cutting off portions of the active river channel (Figure 2c-2). The most important reservoir sandbody in a high-sinuosity channel belt is the point bar (Figure 2c-3). Point bars develop on the inner portion of

35、 each meander loop where the flow is slower allowing the sand to drop out. The opposite side, where the water flows faster and causes erosion, is referred to as the cut bank. Point bars are characterized by a sharp base, a fining-upward character, and are often overlain by rooted soil horizons (Figu

36、re 2c-4). Within the sandbody itself, there is commonly an upward transition from coarse gravel to trough cross-bedded, parallel-laminated, and rippled sandstone (Figure 2c-5).A secondary type of sandbody associated with high-sinuosity fluvial systems is the crevasse splay (Figure 2c-6). A crevasse

37、splay is formed when a river breaks through a levee at floodstage and deposits its material on the floodplain. Crevasse splays typically are formed by the deposition of suspended sediment and are therefore finer-grained and siltier than point bars. The overall shape of a crevasse splay is lobate, su

38、ch that they appear lenticular in sections normal and oblique to the flow direction, but triangular in sections parallel to the flow direction (Figure 2c-7). In addition to point bars and crevasse splays, other elements of high-sinuosity fluvial systems include levees, swamps, oxbow lakes, and flood

39、plain deposits. Levees are elevated areas adjacent to the river channel containing overbank deposits of siltstone and very fine sand. They grade laterally into finer grained silts and clays of the floodplain and black organic-rich muds characteristic of swamps (Figure 2c-8). Floodplain sediments are

40、 distinguished in core by their red, oxidized nature whereas swamps appear as rooted mudstones or coals. Oxbow lakes are crescent-shaped bodies of standing water in the abandoned channel (oxbow) of a meander loop (Figure 2c-9). Fine-grained silts and clays referred to as abandoned channel-fill event

41、ually fill these lakes.Within a high sinuosity fluvial system, permeabilities are highest in the point bar and channel fill sands (Figure 2c-10). Crevasse splay permeabilities are typically 1-2 orders of magnitude lower, whereas levee and floodplain deposits are considered non-pay. A key element in

42、determining whether these types of reservoirs can be drilled and produced is the degree to which reservoir sandbodies are connected. In a low net-to-gross reservoir, sandbodies may not be connected, or may only be connected in a few places along the length of the channel belt (Figure 2c-11). As the

43、net-to-gross ratio increases, connectivity will increase such that not only will all the sandbodies be in pressure communication, but it will also be possible to effectively sweep them using secondary recovery processes such as waterflooding. The key is for the system to be sufficiently sand-rich an

44、d for there to be enough accommodation space so that sandbodies will erode into each other to form amalgamated channel belts across a broad area (Figure 2c-12). These creates more sand-prone areas that can be imaged from seismic and targeted with wells (Figure 2c-13). Most high sinuosity fluvial sys

45、tems are complex, ranging from amalgamated, areally extensive sandbodies to isolated single sandbodies. A good example of this is the Stratton Field of southeast Texas which contains multiple sandbody types that are being delineated with the help of seismic data. (Figure 2c-14). Table 2c-1 summarize

46、s the typical reservoir characteristics of high-sinuosity fluvial systems and how to recognize them from other depositional systems, including low-sinuosity fluvial systems. It should come as no surprise that low-sinuosity and high-sinuosity systems are end members, and that some fluvial systems sho

47、w characteristics of each (Figure 2c-15). Only through the integration of sufficient core, log, and seismic data can the true nature of each system be known.2d. Eolian Systems. Eolian sand dunes produce hydrocarbons from the Permian Rotliegendes Formation of the North Sea, Jurassic strata in the Gul

48、f of Mexico, and numerous other locations. Eolian reservoirs are commonly not as thick as those of other depositional systems, but can be of very high quality due to their clean, well-sorted nature. Deserts cover approximately 20% of the earths land surface, but eolian dunes (Figure 2d-1) only cover

49、 about one-quarter of the deserts while the rest of the area consists of alluvial fans, plays, stony plains, and eroding highlands. These dunes come in many shapes and forms as a function of wind direction and velocity (Figure 2d-2).In eolian systems, sand is transported by three major processes: sa

50、ltation, suspension and surface creep (Figure 2d-3). By far, the dominant process is saltation which accounts for approximately 90% of sand transport. Saltation is a complex process of downwind grain movement by collision and bouncing. Saltating grains form a relatively dense layer that moves up the

51、 shallow-dipping (stoss) side of each sand dune and is deposited on the steeply-dipping (lee) side of the dune. Saltating grains are deposited by four processes: grainfall, wind ripple migration, avalanching, and adhesion (Figure 2d-4). In general, avalanche and wind ripple deposits are the main dun

52、e bedding structures that are preserved.Most eolian dune stratification is dominated by large-scale cross bedding (Figure 2d-5). A cross section through a series of migrating dunes (Figure 2d-6) shows that the preserved portion only represents a fraction of the original dune height. Planar surfaces

53、separate the preserved dune bedsets which are generally one to two meters thick. A major control on stratification within dune systems is the level of the water table at the time of deposition (Figure 2d-7). Changes in the height of the water table preserve the dunes and can produce horizontal trunc

54、ation surfaces of regional extent called supersurfaces. At times when the water table is at or above ground level, fine grained silts, algal mats, and evaporate deposits may accumulate in lakes and other wet portions of interdune areas (Figure 2d-8). Depending upon changes in the height of the water

55、 table and the amount of sand, wet eolian systems can become dry or visa-versa (Figure 2d-9)Eolian systems demonstrate contrasts in reservoir properties ranging from the core-plug scale to the entire reservoir. At the core plug scale, variations in grain size and sorting can result in large variatio

56、ns in porosity and permeability. Figure 2d-10 shows a permeability value from a core plug compared with mini-permeameter values from the same core. The mini-permeameter values range from less than 0.5 millidarcies to 38.5 millidarcies, showing that a single core plug does a poor job of capturing the

57、 permeability variation inherent in these types of rocks. At a bedding scale, grain size variations in dune sheets and interdune deposits create both high quality reservoir intervals and permeability baffles (Figure 2d-11). This presence of these baffles creates complex fluid flow patterns within th

58、e reservoir (Figure 2d-12). Table 2d-1 summarizes the typical reservoir characteristics of eolian systems and how to recognize them from other depositional systems.2e. Alluvial Fan Systems. Alluvial fans are directional landforms that begin at a point source along a mountain front and spread-out dow

59、ndip with an accompanying decrease in grain size and an increase in sorting. The most distinctive feature of alluvial fans is their form. Their characteristic shape results from sediment-charged flows exiting the mountain front at a point source and spreading out along a wide arc (Figure 2e-1). Thei

60、r relatively steep slope (typically 2-12 degrees) produces topographic relief of 300 to + meters across the fan.Types of fans include fan-deltas which terminate into a standing body of water, terminal fans which form where topographically confined rivers drain into an unconfined lowland (Figure 2e-2

61、), and bajadas which are a series of coalescing alluvial fans along a mountain front. Reservoir quality sand is most commonly located along the margins of these fans, while basin-margin faulting and downdip pinchouts of these sediments provide excellent trapping mechanisms. (Figure 2e-3). Alluvial f

62、ans begin to form when steep slopes of bedrock erode to produce loose masses of soil and rock fragments called colluvium. As water from rainfall or snowmelt is added, the masses become unstable and slide downhill. This process mixes the sediment, entraining air and water and transforming the slide i

63、nto a gravity flow. The flow races down the fan until dewatering and a decrease in slope cause the shear strength of the mixture to exceed the downhill pull of gravity, inducing deposition. The resulting deposit is poorly-sorted and generally massive or planar-stratified due to rapid deceleration of

64、 the flow.Alluvial fans are formed by two major types of gravity flows; debris flows and fluidal flows. Debris flows contain sand to boulder-sized clasts that are supported by a clay + water slurry (Figure 2e-4). Large debris flows can be up to 6 feet thick and may cover the entire fan. Debris flow

65、fans have constant slopes of 5-15 degrees and downlap onto basin floor deposits (Figure 2e-5). Debris flow processes dominate fans in rugged, semi-arid regions containing glacial or volcaniclastic rocks. Fluidal flows contain sand and gravel carried downslope as bedload or suspended sediment that is deposited as sheetfloods or streamflows (Figure 2e-6). Sheetflood fans are characterized by catastrophic, turbulen