Hybrid Artificial Lift Strategies for Unconventional Reservoirs

Production rates in unconventional reservoirs are directly related to the reservoir volume stimulated (Stimulated Reservoir volume – SRV) during fracture treatments. Logs and data taken from permanent downhole sensors permit observation of SRV behavior and visualization of interaction, cross flow, interference and inflow performance which have led to strategies that increase total hydrocarbon recovery. We recognize differences with varying reservoir conditions and the need for specific local data. Marcellus formations require choking natural flow production to avoid complications at dew point when liquid phases appear while some Permian formations require lift assistance from flow back through later stages of the life cycle of the well. In conventional reservoirs, artificial lift suppliers insist on inflow performance ratio (IPR), producing fluid level or producing bottom hole pressure along with other fixed parameters to design and supply an artificial lift system. In unconventional wells, the reservoir is a defined by the “SRV”, or network of fractures, microfractures and natural fractures that are much more limited in volume and capacity and where the IPR concept fails to provide the thumb print it did with conventional reservoirs. Many of these wells go from frac fluid recovery to low pressure gassy production within 24 months. Well bore geometries can create gas slugging while completion technologies introduce a need for tolerance to solids. Recent publications identify the need for increased joint work between operators and industry specialist to improve all aspects of hydrocarbon recovery. Artificial lift suppliers are meeting this challenge by developing hybrid or flexible lift strategies with improved components. This paper presents a cost-effective hybrid or flexible artificial lift well completion that accommodates multiple lift systems without workover and with permanent downhole sensors or memory gauges to monitor performance and plan lift system modifications as the well changes. The flexible lift well completion allows for application of various jet pump solutions, gas lift solutions, velocity string and plunger lift solutions that respond to the widest variety of lift needs. The paper includes guidelines for selection, equipment arrangement, application ranges and limitations with specifics on available solutions.