Design A Lift System

[Gabelo Camphire]

Anywayafter the interview was over, I wondered what kind of a system I would actually be happy about committing to a source repo if I was actually tasked to come up with it at work. And thus, I began going down a rabbit hole of designing the components of a building elevator system with details all the way down to the button, light, and motor controls :/

Nope! If we did that, 1. we would introduce a circular dependency and tightly couple the interfaces. 2. ElevatorShaft composes an Elevator, thus needs to know about IElevator. However, Elevator need not know about IElevatorShaft.

We still want the callbacks to happen but have the objects be loosely coupled. One way to achieve the necessary communication and still maintain decoupling between the interfaces is through the Delegate Pattern. i.e, IElevator would communicate with an IElevatorDelegate for its back and forth communication needs. In the concrete implementation, the same object (the concrete ElevatorShaft instance) will satisfy the needs of both the IElevatorShaft and IElevatorDelegate, but the interfaces are not coupled. This might not seem that important, but it helps a lot with testability where we can pass different fake and mock those methods independently.

AVENTOS top takes up little space in cabinets and in warehouses. The hardware is designed so that you only need a few different components but still have full design freedom: the symmetrically designed lift mechanisms and levers are suitable for different sizes of wall cabinets and compatible with all motion technologies. What's more, the same cover cap can be used for HF top, HS top and HL top. This saves decision making when it comes to selection, ordering and handling.

Lift systems in wall cabinets are particularly useful because they give users full freedom of movement as doors move up and out of the user's way. While the kitchen is being used, the lift systems can remain open and out of the way, so that storage items are always within reach.

AVENTOS top combines easy opening with integrated BLUMOTION, making opening and closing cabinets a whole new experience. To incorporate handleless wall cabinets, simply equip the lift system with a motion technology like SERVO-DRIVE or TIP-ON.

Blum stands for quality, innovation and great customer service. We manufacture products such as drawer runners, hinges and lift systems that create an easier workflow for all cabinetry throughout the home.

Ideally, an artificial-lift system should be chosen and designed during the initial planning phase of an oil field. However, in the haste to get a field on production, artificial lift may not be considered until after other production facilities are designed and installed. It is difficult to choose and install the optimum artificial-lift system after the surface production facilities have been installed. This is especially true in the case of gas lift.

Only the gas fundamentals essential to the design and analysis of gas lift installations and operations are discussed in this section. The more important gas calculations related to gas lift wells and systems can be divided into these topics:

Most production equipment affects the design of a gas lift system, so it is best to design the gas lift system concurrently with the design of surface facilities. The entire purpose of a gas lift system is to reduce the bottomhole flowing pressure of the well. Anything that restricts or prevents this from occurring will have an impact on the system and must be considered in the design.

Consideration of gas lift operations should be a prime factor in sizing the hole for the desired oilwell tubulars. This is particularly true in offshore wells where all of the downhole gas lift equipment, except the valves, is installed during the initial completion. In on-shore fields, gas lift affects the size and location of gathering lines and production stations. Artificial lift should be considered before a casing program is designed. Casing programs should allow the maximum production rate expected from the well without restrictions. Skimping on casing size can ultimately cost lost production that is many times greater than any savings from smaller pipe and hole size. The same is true in flowline size and length. Production stations should be relatively near the producing wells. In most cases, increasing the size of the flowline does not compensate for the backpressure generated by the added pipe length. Any item of production equipment that increases backpressure at the wellhead, whether it be wellhead chokes, small flowlines, undersized gathering manifolds and separators, or high compressor suction pressure, seriously impacts the operation of a gas lift system. Fig. 1 illustrates the effect of backpressure on injection-gas requirement and fluid production in a 6,900-ft gas lift well.[1]

Choosing a proper injection-gas pressure is critical in a gas lift system design. [2] Several factors may affect the choice of an injection-gas pressure. However, one primary factor stands out above all others. To obtain the maximum benefit from the injected gas, it must be injected as near the producing interval as possible. The injection-gas pressure at depth must be greater than the flowing producing pressure at the same depth. Any compromise with this principle will result in less pressure drawdown and a less efficient operation. High volumes of gas injected in the upper part of the fluid column will not have the same effect as a much smaller volume of gas injected near the producing formation depth because the fluid density is reduced only above the point of gas injection.

The equilibrium curve[1] illustrates the effect of injection-gas depth on a particular well. The equilibrium curve is established by determining the intersection of the formation-fluid pressure gradient below the depth of gas injection with the produced gas lift gradient above the depth of gas injection for various producing liquid rates (See Fig. 2). In Fig. 2, the intersections of the flowing formation-fluid pressure-gradient traverses for a 400-B/D rate and a 600-B/D rate with the flowing total (formation plus injection gas) -pressure-gradient traverses above the point of gas injection to the surface for both rates are shown. If intersections are established for a large number of rates, as are shown in Fig. 3, the points can be connected and will form what is referred to as an equilibrium curve. When injection-gas pressure traverses are drawn from the surface, it is possible to determine the maximum gas lift rate from the well for various surface injection-gas pressures. Referring again to Fig. 3, a 1,200-psig surface injection-gas pressure would gas lift this well at a rate slightly above 600 B/D.

Less downhole equipment may be required when higher injection-gas pressures are used (see Fig. 4). The higher injection-gas pressure provides a greater pressure differential between the injected-gas pressure and the flowing tubing pressure; thereby, allowing a greater spacing between valves. Thus, fewer mandrels and valves are required to reach the maximum injection-gas depth. Note that in Fig. 4, the 800-psig design reaches only the depth of 4,817 ft and requires seven gas lift valves. In comparison, the 1,400-psig design uses only four gas lift valves to reach the full depth of the well at 8,000 ft. The maximum pressure drawdown at the formation with the 800-psig injection gas is only 210 psi (2,200 to 1,990) compared to 1,010 psi (2,200 to 1,190) when 1,400-psig injection gas is used.

Only the basic conditions that must be met to ensure the most efficient injection-gas pressure to maintain operating pressure for a given well have been discussed. A variety of other factors can affect the selection of the most efficient surface injection-gas pressure. These may include:

The selection and design of compression equipment and related facilities must be closely considered in gas lift systems because of the high initial cost of compressor horsepower and the fact that this cost usually represents a major portion of the entire project cost. In most instances, the injection-gas pressure required at the wellhead determines the discharge pressure of the compressor. Higher injection-gas pressures increase the discharge pressure requirement of the compressor, which is translated into a related increase in the compressor horsepower required for a given volume of gas. However, if the gas lift system is designed properly, the related decrease in gas volume requirements will result in an improvement in overall operating efficiency.

The total injection gas required for a continuous-flow gas lift well may be determined by well-performance prediction techniques. Well-performance calculations are discussed later in this chapter, but they are typically obtained by simultaneously solving the well inflow and well outflow equations. Well inflow, or fluid flow from the reservoir, can be simulated by either the straight line pressure drawdown (PI) or the inflow performance relationship (IPR) methods. [3] Likewise, well outflow, or fluid flow from the reservoir to the surface, is typically predicted by empirical correlations such as those presented by Poettmann and Carpenter, [4] Orkiszewski, [5] Duns and Ros, [6] Hagedorn and Brown, [7] Beggs and Brill, [8] and others. Once typical gas volume requirements for individual wells are determined, totals for the entire field can be calculated.

The importance of gas lift valve performance in the design of a gas lift installation is primarily dependent upon the maximum required injection-gas rates through the gas lift valves to unload and gas lift a well. Dynamic testing of gas lift valves indicated a noticeable difference in the performance of the 1-in.- and 1.5-in.-OD gas lift valves. Although both OD of these gas lift valves had the same port size, the 1.5-in.-OD valve with the larger bellows had a much higher injection-gas throughput rate for the same increase in the injection-gas pressure above the initial valve opening pressure. For this reason, the larger-OD gas lift valve with a 0.77-in.2 bellows area is recommended for gas lifting high-rate wells with large tubing.

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