Wells gas lift

Gas lift wells are treated by the four methods described above. The batch is generally accomplished with a weighted inhibitor because of the high water level encountered. The weighted inhibitor should be selected on release rate. Gas lift wells should be treated by squeeze if the corrosion occurs below 

Some gas wells are completed with a macaroni string, a kill string, or a bottom-hole injector valve in a packer that permits communication from the surface to the bottom of the well. Wells completed in this manner can be treated by batch or continuous injection through the kill string. 

Gas lift wells are sometimes treated by injecting the inhibitor with a chemical pump into the lift gas line. This inhibitor gives protection only from the operating valve to the surface. For this kind of application continuous injection-type inhibitors or batch-type inhibitors are effective. It is best to inject at the well, but injecting at the compressor is also possible. 

The compressed gas will be distributed to a number of wells. In these cases it becomes necessary that both closest and farthest wells from the point of chemical injection be monitored closely. This shows whether good inhibitor distribution throughout the system is being obtained. 

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An example of an application of CAO is its use in optimising the distribution of gas in a gas lift system (Fig. 11.3). Each well will have a particular optimum gas-liquid ratio (GLR), which would maximise the oil production from that well. A CAO system may be used to determine the optimum distribution of a fixed amount of compressed gas between the gas lifted wells, with the objective of maximising the overall oil production from the field. Measurement of the production rate of each well and its producing GOR (using the test separator) provides a CAO system with the information to calculate the optimum gas lift gas required by each well, and then distributes the available gas lift gas (a limited resource) between the producing wells. 

Suction throttle valves are common in gas-lift service to minimi/c the action of the flare valve. Flow from gas-lift wells decreases with increased back-pressure. If there were no suction valve, the flare valve may have to be set at a low pressure to protect the compressor. With a suction valve it may be possible to set the flare valve at a much higher pressure slightly below the working pressure of the low-pressure separator. The difference between the suction valve set pressure and the flare valve set pressure provides a surge volume for gas and helps even the flow to the compressor. 

L. Sinegre, N. Petit, and P. Menegatti, "Predicting instabilities in gas-lifted wells simulation", American Control Conference, ACC, Minneapolis, Minnesota, USA, 2006. 

B. Jansen, M. Dalsmo, L. Nokleberg, K. Havre, V. Kristiansen, and P. Lemetayer, "Automatic Control of Unstable Gas Lifted Wells", SPE Aimual Technical Conference and Exhibition, Houston, Texas, USA, 1999. 

G. O. Eikrem, L. s. Imsland, and B. Foss, "Stabilization of Gas Lifted Wells Based on State Estimation," Inti. Symp. on Advanced Control of Chem. Processes, Hong Kong, China, 2004. 

H. H. J. Bloemen, S. P. C. Belfroid, and W. L. Sturm, "Soft Sensing for Gas-Lift Wells", SPE Annual Technical Conference and Exhibition, Houston, Texas, USA, 2004. 

Continuous injection of corrosion inhibitors is practiced in once-through systems where slugs or batch treatment cannot be distributed evenly through the fluid. This method is used for water supplies, oil field injection water, once-through cooling water, open annulus oil or gas weUs, and gas lift wells. Liquid inhibitors are injected with a chanical injection pump. These pumps are extremely reliable and require little maintenance. Most chemical injection pumps can be adjusted to deliver at the desire injection rate (Chen et al. 2010). 

Figure 9.18 provides an overview of the application envelope and the respective advantages and disadvantages of the various artificial lift techniques. As can be seen, only a few methods are suited for high rate environments gas lift, ESP s, and hydraulic systems. Beam pumps are generally unsuited to offshore applications because of the bulk of the required surface equipment. Whereas the vast majority of the world s artificially lifted strings are beam pumped, the majority of these are stripper wells producing less than 10 bpd. 

The use of large compressors is probably more prevalent in oil field facilities than in gas field facilities. Oil wells often require 1 Tee pressure and the gas that flashes off the oil in the separator must be compressed in a flash gas compressor. Often a g i lift system is nei help lift the oil to the surface. As described in Volume 1, a gas li pressor must compress not only the formation gas that is produce. . .. v,. r oil, but also the gas-lift gas that is recirculated down the well. Gas lift i npressors are chaiacterized by both high overall compressor ratios and 1 atively high throughputs. 

The flare valve also allows production to continue momentarily if a compressor shuts down automatically. Even in booster service it may be beneficial to allow an operator to assess the cause of the compressor shutdown before shutting in the wells. In flash gas or gas-lift service, it is almost always beneficial to continue to produce the liquids while the... 

Figure 10 shows the face of the anode. As indicated, there are doubtless some droplets of electrolyte moving in the channels. The fluorine moves these droplets along just like a gas lift pump lifts water in a goldfish bowl cleaner or a swimming pool vacuum. The electrolyte still does not wet the anode very well, but the low-energy situation makes it easier to move electrons from the electrolyte into the carbon base. 

Crude Oil Production. The Tazerka FPSU development is designed to receive 30,000 B/D [4770 m3/d] of produced liquids from up to eight subsea completed wells. All wells have provisions for future gas lifting. Three of these wells also have been designated for water injection. 

When water-wet gas expands rapidly through a valve, orifice or other restriction, hydrates form due to rapid gas cooling caused by adiabatic (Joule-Thomson) expansion. Hydrate formation with rapid expansion from a wet line commonly occurs in fuel gas or instrument gas lines. Hydrate formation with high pressure drops can occur in well testing, start-up, and gas lift operations, even when the initial temperature is high, if the pressure drop is very large. 

The proposed strategies for stabilization of gas-lifted oil wells are offline methods which are unable to track online dynamic changes of the system. However, system parameters such as flow rate of injected gas and also noise characteristic are not constant with respect to time. An adaptive Linear Quadratic Gaussian (LQG) approach is presented in this paper in which the state estimation is performed using an Adaptive Unscented Kalman Filter (AUKF) to deal with unknown time-varying noise statistics. State-feedback gain is adaptively calculated based on Linear Quadratic Regulator (LQR). Finally, the proposed control scheme is evaluated on a simulation case study. 

The gas-lift oil well operation can be described by the following state-space equations [7] ... 

O. M. Aamo, G. O. Eikrem, H. Siahaan, and B. Foss, "Observer Design for Gas Lifted Oil Wells", American Control Conference, ACC, Boston, Massachusetts, USA, 2004. 

Some natural gas wells also produce helium, which can occur in commercial quantities nitrogen and carbon dioxide are also found in some natural gases. Gas is usually separated at as high a pressure as possible, reducing compression costs when the gas is to be used for gas lift or de-... 

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