Abstract

In order to maximize profits from sucker-rod pumped wells in the ever-changing economic situation with rising costs of electric power, installation design must ensure optimum conditions. The paper addresses the key topics of installation design i.e. the proper selection of pumping mode, optimum counterbalancing of pumping units, rod string design. It shows how these factors relate to the reduction of operational costs and the improvement of pumping operations.

After a review of the surface and downhole energy losses in sucker-rod pumped wells, basic considerations on the ways to improve system efficiency are given. The most important tasks is the proper selection of the pumping mode, i.e. the combination of plunger size, pumping speed, stroke length, and rod taper design for lifting the prescribed amount of liquid to the surface. The best pumping mode maximizes the lifting efficiency and, at the same time, reduces prime mover power requirements and electrical costs. The operational efficiency of the surface equipment is improved by using optimum counterbalancing of the pumping unit. To achieve an ideal sucker-rod pumping System the mechanical design of the tapered rod string must be properly made. The paper gives aspects and details of installation design improvements along with practical examples.

Introduction

Partly due to its long history, rod pumping is a very popular means of artificial lift all over the world. Roughly two-thirds of the producing oil wells are on this type of lift. Most oil producing countries are forced to use some kind of artificial lift on the majority of their wells. This is also true for two of the world's biggest producers, the United States and the former Soviet Union. Fig. 1 contains statistical data on oil wells and shows that total well numbers in the two countries are considerably different. Although the USSR had less than one tenth of the US well population, the proportions of well categories are very similar.

Worldwide total produced liquid volumes from rod-pumped wells do not follow the above proportions. Still, sucker-rod pumping is a very popular means of lifting oil. In many countries the economics of oil production is governed by the production costs for sucker-rod pumping.

To maximize profits from rod pumped wells in the present economic situation with rising electrical costs, installation designs must ensure optimum conditions. In the following, basic considerations on ensuring profitable rod pumping operations will be given. The key topics of installation design (pumping mode selection, optimum counterbalance, rod string design) will be addressed and their role in the improvement of sucker-rod pumping operations and the reduction of lifting costs will be discussed.

Increasing the Energy Efficiency of Rod Pumping

In order to increase the profitability of sucker-rod pumping installations, the reduction of operating costs is of prime importance. Since the majority of installations is driven by an electric motor and the cost of electric energy has steadily increased in recent years, energy losses both downhole and on the surface must be minimized.

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