5.1 Introduction

Continuous flow gas lift is a continuation of natural flow with the only difference that lift gas from the surface is artificially injected into the flow conduit. The vast majority (about 90%) of gas-lifted wells are placed on this type of operation. The great popularity of this type of gas lifting comes from its wide range of applicability: liquid production rates from a few hundreds to many tens of thousands of barrels are possible.

Chapter 5 presents a full coverage of the topics related to continuous flow gas lifting. After a detailed description of the basic principles and the basic design of continuous flow installations, the description of system performance is discussed. Since continuous flow gas lifting is a prime application for multiphase flow theories and practice, the description of the well's producing system is based on Systems Analysis (NODAL) principles. The different typical cases are reviewed and analyzed, and the stability of a gas-lifted well's operation is investigated.

Due to its great practical importance, optimization of continuous flow installations is covered in detail. Since the definition of optimum conditions can vary in different situations, all possible cases (prescribed or unlimited liquid or gas injection rates, existing compressor, etc.) of optimizing a single well are discussed, and the proper optimization procedures are fully described. Optimization for a group of wells involves the correct distribution of the available injection gas with different possible objectives in mind, and the proper allocation of lift gas between a group of wells of...