Technical terms:
tectonic forces构造作用力
are those originating beneath the surface that alter the surface configuration of the earth as a result of tectonic (lithospheric) plate movement.
organic material有机质
is matter that has come from a once-living organism
hydrocarbons烃类
an organic compound containing only carbon and hydrogen
overlying rocks上覆岩层
the rocks that covering the reservoir
pools of tar焦油池
Is where the petroleum eventually reached the surface and be collected in
seeps油苗
places where oil has reached
shows 显示
places where oil has reached
impermeable layer of rock不透水岩层
the layer of rock that can't be passed by liquids.
source bed生油层
the original stratigraphic horizon from which petroleum is derived.
shale页岩
a dark fine-grained laminated sedimentary rock formed by compression of successive layers of clay-rich sediment
organic compounds有机化合物
any compound of carbon and another element or a radical
reservoir bed储集层
the stratigraphic horizon in which the petroleum is collected.
anticline背斜
a fold with strata sloping downward on both sides from a common crest.
salt plug盐柱
the salt core of a salt dome
fault断层
a fracture in the continuity of a rock formation caused by a shifting or dislodging of the earth's crust, in which adjacent surfaces are displaced relative to one another and parallel to the plane of fracture
trap圈闭
a device for sealing a passage against the escape of gases, especially a U-shaped or S-shaped bend in a drainpipe that prevents the return flow of sewer gas by means of a water barrier
structural traps 构造圈闭
the traps that hold oil and gas because the earth has been bent and deformed in some way.
Stratigraphic traps 地层圈闭
the traps which are depositional in nature. This means they are formed in place, usually by a sandstone ending up enclosed in shale. The shale keeps the oil and gas from escaping the trap.
marl泥灰岩
a loose and crumbling earthy deposit consisting mainly of calcite or dolomite; used as a fertilizer for soils deficient in lime
fault traps断层圈闭
the traps that hold oil and gas because a fault
fault gouge断层泥
fine-grained material in the fault
fault plane 断层面
The surface along which the break or shear of a fault occurs
salt dome 盐丘
An anticlinal fold with a columnar salt plug at its core
sedimentary beds 沉积层
the stratigraphic horizon in which the settings lied
fossil coral reefs古珊瑚礁
a reef consisting of the fossil of coral consolidated into limestone
pore space孔隙
the pores in a rock or soil considered collectively
sandstone reservoirs砂岩储层
a reservoir lying in the sandstone layer.
fractures 裂隙
A crack or fault in a rock
wedge out尖灭
A wedge-shaped accumulation of sand with the apex downward formed by the filling in of winter contraction cracks.
2. Porosity and Permeability
Technical terms:
permeability 渗透率
permeability is the ability of the formation to conduct fluids.
porosity孔隙度
is defined as the ratio of the void space in a rock to the bulk volume of that rock multiplied by 100 to express in percent.
bulk volume总体积
the total volume
original porosity原生孔隙度
the inborn and natural porosity of the rock
intergranular porosity粒间空隙度
the porosity occurring between the grains
intercrystalline porosity 晶间孔隙度
The porosity occurring between the ribs
oolitic porosity 鲕状孔隙度
induced porosity次生孔隙度
The porosity produced by induction.That is, affected by external causes.
coring 取心
The use of a core barrel (hollow length of tubing) to take samples from the underground formation during the drilling operation
cementing胶结
A chemically precipitated substance that binds particles of clastic rocks
total porosity总孔隙度
is the ratio of the total void space in the rock to the bulk volume of the rock
effective porosity有效孔隙度
is the ratio of the interconnected void space in the rock to the bulk volume of the rock, each expressed in per cent.
in-place testing现场测量
an in-site measurement occurring at the same time the sample is checked
single-phase fluid saturation单相流体饱和
one of the phases reach the saturation state in the rock.
interstitial water间隙水
Subsurface water contained in pore spaces between the grains of rock and sediments
effective permeability有效渗透率
is introduced to describe the simultaneous flow of more than one fluid
fluid phase液体相
a chemically and physically uniform quantity of fluid that can be separated from a nonhomogeneous mixture
flow network流体网络
a flow network is a directed graph where each edge has a capacity and each edge receives a flow.The amount of flow on an edge cannot exceed the capacity of the edge.
capillary properties毛管性质
Capillary property, is the ability of a liquid to flow against gravity where liquid spontaneously rises in a narrow space such as a thin tube, or in porous materials such as paper or in some non-porous materials such as liquified carbon fibre. This effect can cause liquids to flow against the force of gravity or the magnetic field induction. It occurs because of inter-molecular attractive forces between the liquid and solid surrounding surfaces.
gas cap气顶
the rock pores in the upper zone that have been filled mainly by gas.
aquifer含水层
an underground bed or layer of permeable rock, sediment, or soil that yields water
oil accumulation石油凝集面
an accumulation of petroleum locally confined by subsurface geologic features. Also known as oil reservoir
saturation饱和度
a condition in which a quantity no longer responds to some external influence
viscosity粘度
resistance of a liquid to sheer forces (and hence to flow)
connate water原生水
water entrapped in the interstices of igneous rocks when the rocks were formed.
electric log surveys电测井方法
In 1928, the Schlumberger brothers in France developed the workhorse of all formation evaluation tools, the electric log and it had become an important methord in modern petroleum engineering.
附（原文）：
1.Generation of Oil and Gas
Petroleum is a result of the deposition of plant or animal matter in areas which are slowly subsiding. These areas are usually in the sea or along its margins in coastal lagoons or marshes, occasionally in lakes or inland swamps. Sediments are deposited along with the organic matter and the rate of deposition of the sediments must be sufficiently rapid that at least part of the organic matter is preserved by burial before being destroyed by decay. As time goes on and the area continues to sink slowly (because of the weight of sediments deposited or because of regional tectonic forces构造作用力, the organic material有机质 is buried deeper and hence is exposed to higher temperatures and pressures. Eventually chemical changes result in the generation of petroleum, a complex, highly variable mixture of hydrocarbons烃类, including both liquids and gases (part of the gas being in solution because of the high pressure). Ultimately the subsidence will stop and may even reverse.
As the great weight of the overlying rocks上覆岩层 and sediments pushed downward, the petroleum was forced out of its birthplace. It began to migrate. Seeping through cracks and fissures, oozing through minute connections between the rock grains, petroleum began a journey upward. Indeed, some of it eventually reached the surface where it collected in large pools of tar焦油池. Places where oil has reached the surface are called ‘seeps’油苗 or ‘shows’显示. However, some petroleum did not reach the surface. Instead, its upward migration was stopped by an impervious or impermeable layer of rock.不透水岩层 It lay trapped圈闭 far beneath the surface. The oil and gas tend to rise and will eventually reach the surface of the earth and be dissipated unless they encounter a barrier which stops the upward migration. Such a barrier produces a trap.
Four prerequisites先决条件 are necessary for oil (and gas) to accumulate in commercial quantities in an area: (1) The oil originates in a source bed生油层, and a marine shale页岩, once a black mud黑泥 rich in organic compounds有机化合物, is thought to be a common source rock. (2) The oil then migrates to a permeable reservoir rock, and to do this it may travel for long distances both vertically and horizontally. Oil cannot move through the tiny openings of the shale source beds rapidly enough to be extracted profitably. (3) A nonpermeable layer不可渗透层 must occur above a reservoir bed储集层. Since oil is lighter than water, it tends to move upwards through openings and cracks until it encounters impervious beds that it cannot penetrate. The oil may then accumulate beneath the impervious layers. Some gas occurs in solution多变的 within the oil, and if enough is present it separates out to occupy the uppermost region of such a trap. (4) A favorable structure must exist to concentrate the oil, and anticlines背斜, salt plugs盐柱, and faults断层 are common examples.
Types of Traps
A trap（圈闭） is the place where oil and gas are barred from further movement. Geologists have classified petroleum traps into two basic types: structural traps（构造圈闭） and stratigraphic traps（地层圈闭）. Structural traps are traps that are formed because of a deformation in the rock layer that contains the hydrocarbons. About 80 to 90 per cent of the known petroleum reserves occur in structural traps.
An anticline, the simplest and commonest form of petroleum accumulation, is an upward fold in the layers of rock, much like an arch in a building. A porous and permeable reservoir rock must be sealed above by an impermeable cover bed which is fine-grained（细密的）, relatively impermeable bed such as clay, shale,(页岩） marl（泥灰岩）, or salt. Petroleum migrates into the highest part of the fold, and its escape is prevented by an overlying bed of impermeable rock.
Fault traps（断层圈闭） are also common. Again, there must be a porous and permeable reservoir rock that is sealed above by a fine-grained, relatively impermeable bed. But the real trap is provided by the fault, which prevents further updip migration(上升运移） either by the fine-grained material in the fault itself (the so-called “fault gouge（断层泥）” that results from the movement on the fault plane(断层面）) or by the brining of a fine-grained relatively impermeable bed on the other side of the fault to the position that truncates the reservoir.
A salt dome(盐丘） formed when a mass of salt flows upwards under the pressure resulting from the weight of the overlying sediments（上覆沉积）. The salt dome bows up sedimentary beds(沉积层） and seals off disrupted beds(断裂岩层） and so provides traps over and around the sides of the dome.
The trapping mechanism（圈闭机理） of stratigraphic traps is from stratigraphic rather than structural causes. In these, the essential features remain a porous and permeable reservoir rock sealed by a fine-grained relatively impermeable rock, but the configuration of these to form a trap arises from the particular sedimentary process and nature of the resulting sediments. The most obvious forms of stratigraphic trap are fossil coral reefs（古珊瑚礁） such as those of western Canada and Libya. In these, the voids in the reef or reeflike reservoir contain the petroleum which is prevented from leaking out by the clay or shale in which the reef is enveloped. These voids are not like the pore spaces(孔隙） in sandstone reservoirs（砂岩储层), but more solution cavities（溶洞） and fractures(裂隙）. Production rates（产油率） tend to be much higher than from sandstone reservoirs. The frictional resistance（摩擦阻力） to fluid movement tends to be much less, so there is better communication through the reservoir and it can be produced with fewer wells.
Stratigraphic traps tend to be more difficult to locate and may form where tilted reservoir beds are overlain unconformably by impervious layers or where the reservoir beds become thinner up-dip and wedge out（尖灭） within enclosing impervious beds. Thus oil that was once distributed in sparse amounts throughout a very large volume of rock may now be richly concentrated within the uppermost portions of favorable reservoir rocks. Perhaps the commonest form of stratigraphic trap is the wedging or pinching out of a sand. Discontinuous sands（不连续沉积的砂岩）, such as those that formed part of an old river system (“shoe-string” sands（鞋带状砂岩）) are enveloped in fine-grained sediment and may form a trap.
2. Porosity and Permeability
A petroleum reservoir consists of a suitably shaped porous stratum（多孔层） of rock which is capped with an impervious rock. The nature of the reservoir rock is extremely important as the oil is stored in the small spaces or pores which separate the individual rock grains. Sandstones and limestones are generally porous, and in the main these are the most common types of reservoir rocks. Porous rocks may sometimes also contain fractures or fissures, which will add to the oil-storing capacity of the reservoir.
the remaining water which was buried with the sediments. When a significant fraction of the pores is interconnected so that fluids can pass through the rock, the rock is permeable. Permeability(渗透性） permits the gas, oil and water to separate partially because of their different densities.
Porosity孔隙度 is defined as the ratio of the void space in a rock to the bulk volume总体积 of that rock multiplied by 100 to express in percent. Porosity may be classified according to the mode of origins (1) original and (2) induced. Original porosity原生孔隙度 is typified by the intergranular porosity粒间空隙度 of sandstones and the intercrystalline and oolitic porosity晶间和鲕状孔隙度 of some limestones. Induced porosity次生孔隙度 is typified by fracture development as found in some shales and limestones and by the vugs or solution cavities commonly found in limestones. Rocks having original porosity are more uniform in their characteristics than those rocks in which a large part of the porosity is induced. For direct quantitative measurement of porosity, reliance must be placed on formation samples岩样 obtained by coring取心.
In dealing with reservoir rocks储集层岩石, it is necessary, because the cementing materials胶结物 may seal off a part of the pore volume, to define total porosity总孔隙度 and effective porosity有效孔隙度. Total porosity is the ratio of the total void space in the rock to the bulk volume of the rock；effective porosity is the ratio of the interconnected void space in the rock to the bulk volume of the rock, each expressed in per cent. From the reservoir-engineering油藏工程 standpoint, effective porosity is the quantitative value定量值 desired, as this represents the space which is occupied by mobile fluids可流动流体. For intergranular materials晶粒间物质, poorly to moderately well cemented, the total porosity is approximately equal to the effective porosity. For more highly cemented materials胶结物质, significant difference in total porosity and effective porosity values may occur.
Permeability is the ability of the formation to conduct fluids （formation fluid conductance capacity）. The measurement of permeability, then, is a measure of the fluid conductivity流体传递能力 of the particular material. It can be determined from samples extracted from the formation or by in-place testing现场测量. So far permeability is referred to rock conditions where a single-phase fluid saturation单相流体饱和 was considered. In petroleum reservoirs, however, the rocks are usually saturated with two or more fluids, such as interstitial water间隙水, oil and gas. Effective permeability有效渗透率 is introduced here to describe the simultaneous flow of more than one fluid. In the definition of effective permeability each fluid phase液体相 is considered to be completely independent of the other fluids in the flow network流体网络.
The effective permeability is a relative measure of the conductance of the porous medium空隙介质 for one fluid phase when the medium is saturated with more than one fluid. This definition of effective permeability implies that the medium can have a distinct and measurable conductance to each phase present in the medium.
Fluid Content of Reservoir
In a reservoir rock, the distribution of fluids depends on their densities and on the capillary properties毛管性质 of the rock. Generally speaking, if a reservoir rock contains uniform均匀分布的 pores, and if the pores are evenly distributed均匀分布的, there will be three zones of fluids流体区 in the trap: an upper zone, a middle zone, and a lower zone. The rock pores in the upper zone have been filled mainly by gas. This part of the trap is the gas cap气顶. In the middle zone, the pores have been filled mainly by oil with gas in solution. In the lower zone, the rock pores have been filled by water.
Although the structural traps in which oil accumulates exist in various forms, the oil usually occurs in association with gas and salt water. A certain amount of water always occurs together with the oil in the middle zone. The proportion of water to oil is usually about 10 to 30 percent. Water also occurs in the gas cap, but the proportion of water to gas is frequently lower than the proportion of water to oil. However, while some interstitial water隙间水 is always present in the oil zone含油带, the latter is not always underlain by a continuous body of water. Where a considerable volume of water does underlie the oil in the same sedimentary bed it is referred to as the “aquifer含水层”, and being under pressure also, it contributes to the total energy of the reservoir. The oil itself, when under pressure, contains an appreciable quantity of dissolved gas. The actual amount of gas will be governed by the pressure and temperature inside the reservoir, and the oil is said to be “saturated已饱和” if it cannot dissolve any more gas under these particular pressure and temperature conditions. On the other hand, the oil is said to be “undersaturated未饱和” if it could dissolve more gas at the same pressure and temperature. In many cases there can be more gas in the reservoir than the oil is capable of holding in solution. This extra gas being lighter than the oil, will have formed a “gas cap气顶” above the oil accumulation石油凝集面. If the pressure of a saturated oil reservoir is reduced for any reason, gas will come out of solution, and this is an important factor in the production of oil from the reservoir. It is also possible to find accumulations of gas which are not associated with oil, as is the case in the Southern North Sea.
The reservoir crude may range from a very heavy viscous (i. e., thick) oil, containing little or no dissolved gas under very low pressure, to an extremely light, thin, straw-colored oil containing a large amount of dissolved gas under considerable pressure. The viscosity粘度 of the oil depends roughly on its gravity and also to a large extent on the quantity of gas which it holds in solution. The less viscous (i. e., the thinner) an oil is, and the more gas it has in it, the more readily will it flow through the interstices间隙 of the rock into the bottom of the well. The interstices of the whole of the reservoir rock were originally occupied by salt water. When the oil migrated into the upper part of this rock, it displaced the salt water from it. Not all of the salt water was displaced, however, and a certain amount remained in the interstices of the rock along with the oil. This remaining water is called “connate water原生水” or “interstitial water,” and has to be taken into account when working out the volume of oil present in the reservoir rock. The percentage of this water can be measured by means of electric log surveys.电测井方法
