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Artificial Lift Techbook 2016

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ARTIFICIAL LIFT TECHBOOK: TECHNOLOGY 22 | May 2016 | While unconventional wells do present rapidly changing conditions and signifcant production of solids and abrasives, the selection of an appropriate artifcial lift system is no different from any other well, according to Schlumberger's Griffths. "A diligent artifcial lift engineer will ensure that the right artifcial lift system is deployed in the right well at the right time by adopting a production system life cycle value perspective. Life cycle value may be defned as life cycle revenue, from ultimate recovery, minus the total cost of ownership phased/ discounted over the life cycle," he said. "This may sometimes confict with short-term production targets particularly in times of industry downturn. To evaluate the life cycle value of the vari- ous options, the artifcial lift engineer must determine and respect the numerous constraints on the well and/ or the production system. Some constraints may be related to fow rate, some to drawdown, and some may be nontechnical in nature. The prevailing constraint will change with time. Only when these matters are considered and continually reassessed will the selec- tion and design of artifcial lift system be optimum." In addition to the numerous design constraints, there are other factors to consider in the design process, said Mike Berry, an independent petro- leum engineer. "These wells have such a rapid drawdown. For example, you'll start off with a jet pump or an ESP [electric submersible pump] and you'll get a high production rate early in the life of a well," he said. "But then the well drops off so fast that if you are using an ESP, you're going to drop below the design rate of the ESP before it should, theoretically, meet its end of life. You're going to have to either change to a smaller ESP or go to something like a rod pump. You end up installing two different infrastructures. "You need to think ahead of time what facilities are going to be needed and then ask if it is really necessary to build multiple infrastructures. You should determine if you can live with the lower rate until you get down to something you can handle with just a single lift system," Berry said. "While time is money and it is critical to get that maximum rate right away, you need to determine how much of an economic gain are you losing by having to put in and learn how to use multiple lift systems?" Sandy challenges Long a nemesis to pumps and motors, the abun- dance of sand and proppants used in unconven- tional wells has added another dimension to the common challenge of wear and erosion. Gas lift, jet pumps, ESP and rod pump systems are commonly applied in unconventional wells. "A gas lift system can handle sand and any kind of debris. Sand will pretty much kill a pump. When putting a well on a pumping unit, if the well's not cleaned up enough, you'll have sand issues with your downhole rod pump as well," said Kelly Raper, vice president of sales and cor- porate development for Priority Energy Services. "Gas lift, although in many cases can't produce the fuid that an ESP can, we can obviously pro- duce various rates, from very high rates to very low rates, so gas lift is probably the most economical way to look at doing this because we can vary so much in the different rates." However, there are critical questions to consider before going with a gas lift system. By utilizing a unique wiper and flter coupling assem- bly, the STP helps reduce damage caused by sand to the barrel/plunger interface in reciprocating pumps. (Image courtesy of Weatherford)

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