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1、 Lesson 3 Production Technology3.1 Completion Components3.2 Surface production Facilities3.3 Field Examples of Production Systems3.4 System Performance3.0 Introduction3.0 Introduction Now lets consider the well as part of a dynamic production system.Wells are drilled and logged,maps are revised,and
2、the reservoir begins to take shape as a volume having certain dimensions.(Big ones,hopefully!)But once production begins,the reservoir is only a part of a larger system that includes the reservoir,wellbore,tubing string,artificial lift equipment,surface control devices,gathering lines,separators,tre
3、aters,tanks,and metering devices.计量装置计量装置 All of these elements behave according to their own specific performance relationships,but each,in turn,also depends upon and influences the other elements.Production engineers are concerned with the interaction of these performance relationships as producti
4、on occurs over time,anticipating performance changes and designing the system to maximize recovery of oil and gas economically.3.0 IntroductionThis chapter outlines production system equipment,starting with the completed well and moving along the flow path through the surface facilities.The same pat
5、h is then retraced,but this time focusing on the dynamic flowing performance relationships that govern fluid movement through the system.地面设备地面设备3.0 Introduction3.1 Completion Components Together with the cement sheath holding it in place,the casing performs several important function:supporting the
6、 sides of the hole;preventing communication of fluids and pressures between shallow and deep formations;allowing for control of pressures;providing a base for surface and subsurface equipment.水泥环水泥环A cross section of a typical casing installation is shown in figure 3.1.The number of concentric“strin
7、gs”,their relative sizes and strengths,the setting depths,and cementing techniques will vary according to the depth and drilling program for the well.The conductor prevents the surface hole from caving and it also prevents lost circulation.In offshore situations,the drive pipe is hammered into the m
8、ud to provide a conduit from below the seafloor to the production deck,and the conductor casing is set inside the drive pipe.击入式管子击入式管子循环漏失循环漏失3.1 Completion ComponentsSurface casing provides protection for shallow freshwater formations,and the producing string of casing is set to or through the pro
9、ductive zones,to isolate them and allow for selective completions.There may be intermediate casing strings between surface and production casing if the depth of the well requires it.Each casing string is cemented in place and the production string is perforated across the productive zone.淡水层淡水层生产层生产
10、层技术套管技术套管表层和表层和生层套管生层套管3.1 Completion ComponentsThe central downhole component of a completed well is the production tubing.There are four primary reasons for utilizing production tubing as a conduit for producing fluids:It is relatively easy to remove if problems develop.It isolates producing fluid
11、s from the casing and makes control of the fluids easier.It facilitates circulation of heavy fluids into the wellbore to control the well.Its smaller diameter allows for safety devices and artificial lift equipment to be included in the completion design.It allows for more efficient producing rates
12、from lower productivity wells.生产油管生产油管Tubing is suspended from a tubing hanger within the wellhead at the surface,and the producing zone(s)may be isolated by production packers in the tubing string.A well may be completed with several strings of tubing(dual completion,triple completion,etc.),each ca
13、rrying production from a different zone.Some extremely productive wells produce through casing without tubing,or through both tubing and the casing-tubing annulus.3.1.1 Tubing ComponentsThe design of a particular completion depends on:the number and type of productive zones;the expected pressures an
14、d flow rates;the need to control sand production;the need for artificial lift or stimulation;and the regulations governing operations in the area.Figure 3.3 shows schematic examples of a number of typical completions.In addition,the following definitions and associated figures describe the most comm
15、on components of those completion examples.Packer:The packer seals the casing-tubing annulus with a rubber packing element,thus preventing flow and pressure communication between tubing and annulus.Packers are designed either to remain in the well permanently or to be retrieved if future downhole wo
16、rk is required.封隔器封隔器3.1.1 Tubing ComponentsMultistring Packer:The multistring packer seals the casing-tubing annulus where more than one tubing string is involved.Up to five-string packers are available,but more than a triple completion is rare because of the difficulty of retrieval if problems dev
17、elop.Sliding Sleeve:the sliding sleeve component is a wireline-operated sleeve,which will open or close ports in the tubing to allow fluid in or out.滑套滑套多管柱封隔器多管柱封隔器Tubing Anchor:The tubing anchor is essentially a packer without the sealing element and is designed to prevent tubing but not fluid mov
18、ement.油管锚油管锚Blast Joint:A blast joint is a section of heavy-duty tubing located opposite production perforations in a multistring completion.耐磨接头耐磨接头Safety Joint:The safety joint allows for the parting of an auxiliary tubing string beneath a multiple string packer when the packer is being retrieved.
19、安全接头安全接头Landing Nipple(fig.3.11):Landing nipples are a variety of short tubing components with interior profiles that allow for the wireline setting of plugs,safety valves,chokes,pressure gauges,etc.,within the tubing by using the appropriate locking device.座放短节座放短节Figure3.11 Landing nipple and flow
20、 coupling installation.Courtesy Baker Packers,a Baker Oil Tools Company.Subsurface Safety Valve:This component is a valve assembly within the tubing string,which is designed to close in case of emergency.井下安全阀井下安全阀Figure3.13 Tubing retrievable subsurface safety valve operation:(a)closed,(b)open.Cour
21、tesy Baker Packers,a Baker Oil Tools Company.3.1.2 Surface Flow Control EquipmentThe valves and connections at the top of the well are often referred to collectively as the“wellhead”or“Christmas tree”.The design of the entire arrangement depends on several factors:the expected maximum and operating
22、pressures;the number and sizes of casing strings;the number and sizes of tubing strings;采油树采油树the need for auxiliary equipment,such as subsurface safety valves,electrical conduits for submersible pumps,and chemical injection equipment;the outside environment.onshore,offshore,or subsea;the inside env
23、ironment:CO2 and H2S content of produced fluids or corrosive formation water;辅助设辅助设备备Figure 3.14 shows a typical surface flow control installation for a multiple casing string,single tubing string,flowing well.Figure3.14 Surface flow control installation for a single tubing string,mulyiple casing st
24、ring,flowing well.Courtesyrs Exxon.自流井自流井The casinghead(fig.3.15)is screwed,or welder to the outermost casing stub.CasinghangerCasingspoolHangerCasingheadTubinghangeradapterTubinghangerTubingheadFigure3.15 Casinghead and casing hanger installationg and tubing head and tubing hanger installationg.Cou
25、rtesyrs Exxon.套管头套管头The tubing head performs a function similar to the casinghead,in that it accommodates a tubing hanger,which usually screws onto the top of the tubing string(s)and seals off the casing-tubing annulus with metal-to-metal and/or rubber sealing elements.Often the tubing hanger is fur
26、ther secured by a series of set screws.An adapter(also called a tubing“bonnet”)provides a transition from the tubing head to the arrangement of valves and fittings above the casing and tubing head,used to control flow(the“Christmas tree”).In the Christmas tree,the bottom valve,often called the maste
27、r valve,is the primary means for completely shutting in the well.This and other valves used in the tree are normally gate valves that operate by moving a metal barrier to block the flow stream The produced fluids in the flowing well,before entering the surface flow-line,must pass through the smalles
28、t restriction in the surface flow equipmentthe choke.底阀底阀油嘴油嘴We may wish to maintain a certain flow rate for many reasons:to prevent sand production;to control water or gas productionto maintain the most efficient production rate for a particular reservoir producing mechanism;orto produce the well a
29、t a fixed allowable.a production rate designated by a governmental regulatory agency.In the case of a positive choke,the flow is controlled by alternately inserting various beans with appropriately sized orifices.With an adjustable choke we may vary the flow restriction mechanically without changing
30、 the bean.Tubing pressure is measured upstream from the choke(toward the well).Figure 3.20,3.21 show examples of surface flow control equiprnent for a variety of completions.Figure3.20 Wellhead and Christmas tree for a dual tubing completion utilizing clamp-type connection.From Gray Tool CompanyFigu
31、re3.21 Surface flow control equipment for low-pressure pumping well installation.As section 3.1 has shown,the downhole and wellhead components of a completed well can vary,depending on the complexity of the completion design.Generally,the most important completion components are the tubing string an
32、d the surface choke,because these components usually have the greatest effect on the flowing performance of a well.We have also seen that in some cases,the original completion should be designed in anticipation of future or immediate artificial lift needs.This is an important point that needs to be
33、kept in mind.3.2 Surface Production FacilitiesThe fluid produced from a well is usually a mixture of oil,gas,water,and sediment at elevated temperatures and pressures.The oil alone is a complex mixture of many hydrocarbon compounds,and oils from different reservoirs have different physical and chemi
34、cal characteristics.Formation water may be carried in the gas state as vapor,emulsified as a liquid with the oil,or produced as free water.地层水地层水Surface production facilities are designed to turn this mixture into separate streams of clean,dehydrated oil and gas and safely disposable water.Only then
35、 can the oil and gas be metered and sold,or sent for further processing to a plant or refinery.Of course,the diversity of well fluid mixtures has led to the development of an assortment of vessels to clean and separate these mixtures at various pressures and temperatures.Lets follow the production s
36、tream for an oil well,describing the equipment and its function at each step.3.2.1 SeparationThe produced fluids leave the Christmas tree via a flow Lineusually a 2-or 3-in(5-to 8-cm)pipe,which may be below or above ground at onshore installations,or perhaps on the seafloor for a subsea completion.S
37、ubsea completions are often equipped with TFL or through-flow-line connections whereby the flow line connects to the Christmas tree in a smooth loop.This arrangement allows for production devices(plugs,etc.)to actually be pumped through the flow line and into the tubing,thus eliminating the need to
38、disconnect any Christmas tree fittings.Separators are usually classified by physical shape,and figure 3.22 shows the basic vertical,horizontal,and spherical separator configurations.A conventional separator divides the produced fluid stream into oil and gas,or liquid and gas,and is known as a gas-oi
39、l separator or gas-liquid separator.Sometimes separators are also called“traps.”Figure3.22 Separator configurations气液分离器气液分离器Metering separators accumulate the separated oil,or oil and water,isolate the liquid phases in calibrated chambers,and periodically discharge the measured volumes into separat
40、e outlets.Such separators can be designed to meter only the oil,or both oil and water.Special designs are also available for very viscous oil,or oil that tends to“foam.”计量分离器计量分离器Lets discuss the operation of a typical vertical,two-phase,gas-liquid separator,shown schematically in figure 3.23.The oi
41、l-gas-water mixture enters through an inlet on the side of the tank-shaped vessel.Figure3.23 Conventional vertical separator.Courtesy Sivalls,Inc.The gas phase,which is directed to the upper portion of the vessel,is usually passed through a mist extractor to remove minute liquid droplets entrained i
42、n the gas.Here,three processes act to separate liquid from the gas:flow velocity changes;direction changes;and impingement,or the adherence and coalescence of liquid mist on a surface.A combination of these three processes is incorporated into a coalescing pack-type mist extractor made of knitted wi
43、re mesh or layers of inert particles with shapes designed for maximum surface area.Centrifugal-type mist extractors(fig.3.26)used in vertical separators have a set of vanes that cause the circular motion of gas,throwing the heavier liquid droplets to the wall of the vessel to drain to the bottom.Its
44、 efficiency increases as the velocity of the gas stream increases.Figure3.26Vertical separators are often used on low to intermediate gas-liquid ratio well streams.They are more readily cleaned if sand or paraffin are produced,and occupy less floor space on offshore platforms.However,a vertical sepa
45、rator can be more expensive than a horizontal separator with the same separation capacity.Horizontal separators,therefore,are usually more cost-efficient,especially for high to medium gas-liquid ratio streams,for liquid-liquid separation,and in applications where foaming oil is a problem.Horizontal
46、separators often have closely spaced horizontal baffle plates that extract liquids.A double barrel horizontal separator has a higher liquid capacity because incoming free liquid is immediately drained away from the upper section into the lower.This allows a higher velocity gas flow through the upper
47、 baffled section.Spherical separators are much less common than vertical orhorizontal types.They tend to have lower installation and maintenance costs.They are more compact,but lack the capacity for high gas rates or liquid surges.Separators are sized according to the expected oil and gas production
48、 rates,the necessary operating pressure and temperature,and the oil and gas properties.It is important to remember that the physical and chemical characteristics of the crude oil and gas entering the separator help determine the degree of separation possible at a given operating temperature and pres
49、sure.Separating the gas held as bubbles in the oil,or oil entrained as droplets in the gas,can be accomplished by manipulating the fluid stream.3.2.2 Oil TreatmentIn many oil fields,following the initial gas-oil separation process,the oil must be treated to remove water,salt,or H2S.Most pipeline qua
50、lity oil must have its water content reduced to the 0.2 to 2 by volume range.Because salt water is generally associated with oil in the reservoir,its production along with the oil is not unusual.Almost all well streams contain water droplets of various sizes.水滴水滴The water cut measured on one or seve