New Gas-Lift Concept-Continuous-Flow Production Rates From Deep, Low-Pressure Wells
Authors: DeMoss E.E. , Ellis R.C. , Kingsley G.S. 
Published: December 2007

With this unique chamber system, which involves automatic cycle control and a separate tubing string for venting the formation gas, it is possible to achieve gas-lift production rates of 1,000 BID from 10,000 feet at low flowing bottom-hole pressures. In a field test oil four wells, production increased immediately in three of the wells, and more gradually in the fourth.

Introduction

The Automatic Vent Chamber (AVC) System was developed to overcome the disadvantages inherent in using deep, high-volume lift systems such as large-beam, hydraulic, or electric submersible pumps. These systems require a large initial capital investment and are often expensive to operate and maintain - especially in wells with high gas/liquid ratios or sandy conditions. The capital investment required for an AVC system is especially attractive when there is gas compression equipment already on the lease. Gas-lift systems have proved to be an extremely flexible and economical means of lifting fluid from deep wells, particularly from those with high flowing bottom-hole pressures. However, means of lifting large volumes of fluid from deep, low-formation pressure wells have been limited, Conventional pressure wells have been limited, Conventional chambers have been used with good results, but these systems also have volume limitations. With the advent of the AVC system, a whole new realm of artificial lift was introduced. It is actually two system in one. The chamber system automatically pumps liquids from the chamber to the producing tubing where the upper standing valve producing tubing where the upper standing valve retains the liquid. It then vents the chamber, allowing it to refill. The gas-lift system above the chamber lifts the liquid from the upper standing valve to the surface. Thus the chamber is refilling while the previous chamber load is being lifted by the gas-lift previous chamber load is being lifted by the gas-lift system. Of course, while the chamber is refilling, formation gas is being Produced through the chamber and up the vent tubing. This eliminates the problems experienced with conventional chambers in gaseous wells. The chamber cycles repeat at a rate equal to the well's producing capability. The tubing cycles repeat with each one or two chamber cycles. In summary, the AVC system provides an automatic chamber that can handle formation gas with case and achieve a lower bottom-hole pressure than was ever before possible with gas lift. As with any chamber application, wells with high productivity indices (PI's) are the best candidates, productivity indices (PI's) are the best candidates, but in offshore fields, in subsea work, or on city lots where gas lift is a practical necessity, the AVC system may be economically applied to wells with high bottom-hole pressures and medium to low Pi's. it is felt that the system is particularly suited to fields undergoing secondary recovery.

Production History Production History Four wells have been equipped with AVC systems and each illustrates the effectiveness of the system. Table 1 shows the production history of each well for several months. Each well was equipped with 2 7/8-in. production tubing and 1.900-in. OD vent tubing.

JPT

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