Chapter1 Oil and Gas Fields
◎ 1.1 An Introduction to Oil and Gas Production
The complex nature of wellstreams is responsible for the complex processing of the produced fluids (gas, o il，water, and solids). The hydrocarbon portion must be parated into products that can be stored and/or transported. The nonhydrocarbon contaminants must be removed as much as feasible to meet storage, transport, reinjection, and disposal specifications. Ultimate disposal of the various waste streams depends on factors such as the location of the 金宗瑞
field and the applicable environmental regulations. The overriding criterion for product lection, construction, and operation decisions is economics.
Fig. 1-1is a comprehensive picture of the individual unit operations carried out in field processing. All the various modules shown will not all be prent in every system. Furthermore, the modules ud in a given application may not be arranged in the exact quence shown, although the quence is，in general, correct. The lection and quencing of modules is determined during the design pha of field development.
As shown in Fig. 1-1，the individual phas (gas，liquid工作能力总结
hydrocarbon, liquid water, and solids) should
be parated from each other as early as practical. Individual streams can then be treated with less technical difficulty and more economically. Hartley and Bin Jadid (1989) illustrate how lab and field tests performed before construction can identify and minimize future production and processing problems such as scaling, foaming, emulsion formation, wax depositionand hydrate formation. Processing of the parated streams is now reviewed briefly becau many of the ind工程部职责
ividual unit operations
The Cour of English in O i卜gas Storage and Transportation
Bacteriocide Scale inhibitor
Formation
Seawater Corrosion inhibitor
(b)
Fig. 1-1General field processing scheme,
are discusd in detail in subquent chapters.
1.1.1 Gas Processing
As shown in Fig. 1-1，gas processing begins with treating, if necessary, to remove the acid gas—hydrogen sulfide and carbon dioxide. Both gas are very corrosive when liquid water is prent and hydrogen sulfide is most toxic. Environmental regulations almost always prohibit the relea of significant amounts of hydrogen sulfide to the surroundings. Conversion to elemental sulfur is becoming irlcreasingly necessary.
Gas sweetening113 usually us aqueous solutions of various chemicals. Therefore，sweetening will precede dehydration. Dehydration is often necessary to prevent the for
Chapter 1Oil and Gas Fields
mation of gas hydrates, which may plug high-pressure processing equipment or pipelines at high pressure and at temperatures considerably higher than 32 F (0 C).
Gas that contains considerable amounts of liquefi介绍自己英语
able hydrocarbons (ethane or propane and heavier)⑴ can produce condensate upon compressing or cooling. The condensate may cau difficulty in pipelining or subquent processing. Field processing to remove the natural-gas liquid
s (N G L), sometimes referred to simply as condensate, may be economical or may be required to meet a hydrocarbon dew-point specification⑴. In remote locations such processing is generally avoided if possible. Recovered condensate may, in turn,* have to be stabilized by removing dissolved gaous components to obtain a transportable product1-4-1.
Final disposal of the gas stream depends on the situation. Early in the life of a remote field，before the availability of a pipeline, the gas may simply be flared. It is becoming more common to conrve调查报告范文
the gas by compression and reinjection into the formation with a view to its eventual recovery and sales. Conrvation is often demanded by law；permits to flare are usually temporary and granted only during the initial start-up of production. Environmental restraints may also prevent flaring especially if the gas contains any hydrogen sulfide.
The common situation is to flow the natural gas into a pipeline for sales. Gas pipelines have operating pressure levels of the order of 700 — 1000 psia to allow economical transport in pipes of reasonably small diameter. Compression of the gas to pipeline inlet pressure may be required.
1.1.2 Oil Processing
After free water removal, produced oil often contains excessive residual emulsified water。]. Treatin
g, also called dehydration, is required to reduce the water content to a value acceptable for transportation or sales. Dehydration should be accomplished using the most economic combination of four factors or techniques；namely, residence time，chemical addition, heat, and electrostatic fields. Dilution water must occasionally be added to reduce the salt content of the residual emulsion (i. e. , the sales crude oil) to a suitably low level. In the United States，desalting is usually performed in the refinery⑷；overas，desalting is sometimes performed in the field.
Hydrogen sulfide in crude oil is limited to reduce handling and transportation difficulties becau of its extreme toxicity and corrosivenessL?J. Gas stripping or heating is usually ud for hydrogen sulfide removal or sweetening as is discusd latterly[8].
Crude oil stabilization refers to lowering 我的家乡二年级作文
the vapor pressure to a value that will al
The Cour of English in Oil-gas Storage and Transportation
low safe handling and transport. Vapor pressure control is obtained by stage paration, rcboiled distillation, or a combination of the two. During stabilization some of the more volatile hydrocarbons are removed as vapor and this gas pha entrains hydrogen sulfide and other volatile sulfur compounds from the sour crude oil. Additional sweetening may not be required1"9] •
1.1.3W ater Processing
Produced water (usually saline) is a waste material，but processing is often necessary to render the water suitable for di垃圾分类背景
sposal to the surroundings. Often additional water *frequently a water, is also procesd for waterflooding. The two parate water processing schemes are both shown in Fig. 1-1.
Oil removal is the first treatment for produced waters. C)il-in-water emulsions are difficult to clean up due to the small size of the particles，as well as the prence of emulsifying agents. Suspended solids may also be prent in the water. Types of equipment ud for removing oil and solids include：
• Oil skimmer tanks；
• Plate coalescers；
• Air flotation tanks；
• Hydrocyclones；
• Filtration units.
Before reinjection, the produced water is usually filtered，deaerated if necessary, and treated with biocides. The major goal，of cour, is to prevent rervoir plugging.
Seawater is by far the most commonly ud injection water for pressure maintenance becau of its obvious abundance. Unfortunately, its poor water quality demands extensive treatment. As shown in Fig. 1-1，awater is first treated with shock biocides to kill all organisms and then filtered. Dissolved oxygen is removed cither by chemical scavengers, by gas or vacuum stripping, or by catalytic reaction with hydrogen. This reduces the corrosivity of the water dramatically and inhibits growth of aerobic slime- forming bacteria in the well bore. Then the water is sterilized either by ultraviolet radiation or additional biocide injection to kill bacteria and other micro-organisms. Microorganisms can cau corrosion, plugging of lines and rervoir formation rock, and they can also produce H2S in the formation (Osrroft, 1979). Scale inhibitors are also added before injection into the formation.
Chapter 1Oil and Gas Fields 1.1.4 Sand Treatment
Sand and other solid material may gather in any of the previously mentioned equipment in locations where the velocity and turbulence in the liquid stream is low, such as in the bottom of tanks or on co
alescer plates. Removal of the sand by some type of jetting nozzle or similar arrangement may be necessary. Sand removal is some times carried out by centrifugal cone desanders (Arnold, 1983). The sand itlf may have adhering oil cr emulsion that requires washing before discharge to the surroundings.
1.1.5 Auxiliary Equipment
In addition to the previous operations，shown in Fig. 1-1 . additional equipment is required for important ancillary functions. The are now reviewed briefly.
Test parators with appropriate gas and liquid flowmeters are often provided for periodic measurement of the production rate from individual wells or groups of wells. 5-jch testing is often a legal requirement. Appropriate flowlines. valves, and manifolds 二ust be provided so that the desired wellstreams can be isolated and pasd through the ztsi production parator。0]•This equipment can become quite elaborate if many wells are involved.
In the United States, total oil production is usually measured in lea automatic custody transfer (LACT) unitsL n J that measure oil production volume as well as S&-W rontent. Turbine meters are sometimes ud overas. Gas production rate is generally Measured in orifice-meter installations.
Automatic safety systems are a necessary and integral part of any oilfield facility. Adequate protection must be provided against all unsafe conditions including overpressure. liquid overflow, overheating in fire喝酒礼仪
d heaters, unwanted sources of ignition, and so forth. Vent and flare facilities are required for the safe removal and disposal of gas crolved in both normal and emergency operation.
Recovery of natural gas liquids from waste vapor is often practiced by u of s o-called vapor recovery units (V R U)，consisting of compression and cooling equipment. Emissions are making vapor recovery mandatory in many cas.
Other additional operations include such items as electrical power generation, instrument air supply，as well as fire, drinking, and sanitary water supplies, and wage d:?posaL
