Field Scale Research on Artificial Lift
Authors: Hernandez Ali , Marcano Luisana , Garcia Gonzalo , Machado Miguel , Caicedo Sergio , Rivas Oswaldo 
Published: December 2007

A field test loop to conduct experiments on artificial lift has been built and it is already in operation. A detailed description of the test loop is presented. It consists of a 8000 foot deep well with surface storage capacity of 3000 Br of fluids, gas-liquid separators, surface pumps which are able to handle up to 12000 Br of fluid per day. natural gas supply of 3 MMSCFD at 1500 psi, surface and downhole pressure and temperature sensors, data acquisition system and surface control equipment. It is also presented in this paper the results of the first test program which was carried out on intermittent gas lift. A total of 125 experiments were performed to measure the effect of injection pressure and gas flow rate per cycle on the liquid fallback for different sizes of liquid columns. Injection pressures ranged from 600 to 900 psi, and liquid columns form 200 to 1400 ft were studied. The dynamic response of gas lift pilot valve was studied for the first time, It was found that the behavior of spring loaded and nitrogen charged gas lift pilot valve deviate from currently accepted theoretical behavior in opposite ways. This deviation causes considerable errors on the calculated gas flow per cycle. A general analysis of this deviation is discussed.

Introduction

As reservoir pressures decline, some, form of artificial lift is needed to maintain production of oil wells. Through the years, the Oil Industry has developed a variety of artificial lift methods and during the history of each of those methods, continuous improvements in their technology and application have been achieved. Nevertheless, the Oil Industry still faces the challenge of improving the technology of artificial lift: with ever rising production costs, maintaining the economic life of oil wells is a problem far from being solved.

Due to the complexities encountered in most of the processes of artificial lift, many of the methods that are used today, were improved upon by applying them in real conditions and making necessary changes along the way. Those trial and error procedures were frequently carried out in uncontrolled environments with the end results of having limited applications at a high economic cost. Lab scale research, on the other hand, while important as a first step in any research program, is very limited because its results are difficult to extrapolate to real field conditions.

For all the reasons presented above, performing field scale research on artificial lift in well controlled environments seems like the natural way to approach the problem of improving the technology of artificial lift. Furthermore, in a world were Joint Industry Research Programs are gaining popularity due to the advantage of keeping research and development costs down, having a field scale lab, available to any company in the Oil Industry and custom made for artificial lift research, seems to fit particularly well to current Industry needs.

In this work, a detailed description of a field scale lab that is already in operation in Western Venezuela is given. Surface and downhole facilities are such that a large number of artificial lift methods can be tested at real and controlled conditions. A detailed description of the first research program performed at the field lab is presented. A total of 125 experiments were performed on intermittent gas lift. Even though intermittent gas lift has been in used for many decades, it is in this work that the dynamic behavior of gas lift pilot valve was studied for the first time, This is precisely due to the fact that the amount of compressed gas needed for each cycle cannot be attained in a lab scale test loop. This is then a very clear example that illustrates the need for a field scale lab.