Tubing head pressure

A comfortable margin is maintained between the flowing tubing head pressure (downstream of compression) and the minimum pressure required for export, since the penalties for not meeting contract quantities can be severe. The decision not to install a fourth stage of compression in the above example is dictated by economics. During the final part of the pressure decline above, the field production is of course also declining. 

Routine production tests are performed, approximately once per month on each producing well, by diverting the production through the test separator on surface to measure the liquid flowrate, water cut, and gas production rate. The wellhead pressure (also called the flowing tubing head pressure, FTHP) is recorded at the time of the production test, and a plot of production rate against FTHP is made. The FTHP is also recorded continuously and used to estimate the well s production rate on a daily basis by reference to the FTHP vs production rate plot for the well. 

Sensors on the tree allow the control module to transmit data such as tubing head pressure, tubing head temperature, annulus pressure and production choke setting. Data from the downhole gauge is also received by the control module. With current subsea systems more and more data is being recorded and transmitted to the host facility. This allows operations staff to continuously monitor the performance of the subsea system. 

Monitoring and control of the production process will be performed by a combination of instrumentation and control equipment plus manual involvement. The level of sophistication of the systems can vary considerably. For example, monitoring well performance can be done in a simple fashion by sending a man to write down and report the tubing head pressures of producing wells on a daily basis, or at the other extreme by using computer assisted operations (CAO) which uses a remote computer-based system to control production on a well by well basis with no physical presence at the wellhead. 

Normally acid would be allowed to soak for some time and then back-produced if possible along with the impairing products. One of the advantages of using coiled tubing is that it can be inserted against well head pressure so the well does not have to be killed a potentially damaging activity. 

Fair s method may also be modified to design forced-recirculation reboilers with horizontal tubes. In this case the hydrostatic-head-pressure effect through the tubes is zero but must be considered in the two-phase return Tines to the column. 

For an exchanger AAith alloy parts and a design pressure of 150 Ibf/im, the alloy extras are added. For shell and shell cover the combined alloy-pressure extra is the alloy extra times the shell-side pressure extra/100. For channel and floating-head cover the combined alloy-pressure extra is the alloy extra times the tube-side pressure extra/100. For tube sheets and baffles the combined alloy-pressure extra is the alloy extra times the higher-pressure extra times 0.9/100. (The 0.9 factor is included since baffle thickness does not increase because of pressure.)... 

A tube has failed in one of the four condensers about once every three years. If a condenser tube fails, the affected condenser can be removed from service by closing four isolation valves (propane vapor inlet valve), liquid propane outlet valve, cooling water supply valve, and cooling water return valve). However, if a tube fails, it is essential that the operator close the two propane isolation valves before closing the two water isolation valves. Closing the two water valves first would allow pressure to build on the tube side of the condenser and rupture the tube head. 

The detailed design of the tube bundle must take into account both shell-side and tube-side pressures since these will both affect any potential leakage between the tube bundle and the shell which cannot be tolerated where high purity or uncontaminated materials are required. In general, tube bundles make use of a fixed tubesheet, a floating-head or U-tubes which are shown in Figures 9.62, 9,63 and 9.64 respectively. It may be noted here that the thickness of the fixed tubesheet may be obtained from a relationship of the form ... 

A shell and tube heat exchanger, heat transfer area 50 m1 2 3, floating head type, carbon steel shell, stainless steel tubes, operating pressure 25 bar. 

The tube-plates (tube-sheets) in shell and tube heat exchangers support the tubes, and separate the shell and tube side fluids (see Chapter 12). One side is subject to the shell-side pressure and the other the tube-side pressure. The plates must be designed to support the maximum differential pressure that is likely to occur. Radial and tangential bending stresses will be induced in the plate by the pressure load and, for fixed-head exchangers, by the load due to the differential expansion of the shell and tubes. 

Injection into unsaturated deposits must also consider that when the injected water leaves the injection tubing, it is at atmospheric pressure, and the driving head is lost which lowers injection efficiency. In addition, the capillary and surface tension forces in the void spaces provide resistance to water movement, thus limiting injection efficiency. Injection into only the saturated zone (Figure 8.8b) maintains a positive head pressure on the water until it exits the well screen. This limits the chemical reaction that might occur in the well bore. Since the void spaces are saturated, there are no capillary or surface tension forces to overcome. 

Consider the causes of the pressure drop and the equations to find each. The total pressure drop for fluids flowing through tubes results from frictional pressure drop as the fluid flows along the tube, from pressure drop as the fluid enters and leaves the tube-side heads or channels, and from pressure drop as the fluid enters and leaves the tubes from the heads or channels. 

This unit consists of a steel, aluminium or stainless steel cylinder (preferably furnished with a dip tube), a pressurized head space and a device allowing cooling for long enough to ensure equilibration. 

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