Publisher Summary This chapter focuses on compression, which helps the liquid-loading well to increase the gas velocity to equal or exceeds the critical unload velocity and lowers the pressure on the formation for more production by lowering the wellhead flowing pressure. There are several types of compressors with varying degrees of initial cost, operational cost, and functionality for single-well compression. Compression is often used for field wide compression to lower the gathering system pressure. Compression also helps other methods of artificial lift to different degrees. It might also allow the plunger lift to function where it may not cycle without compression. Lowering the surface pressure of a gas well has two effects, both of which are beneficial for liquid loading—the flowing bottom hole pressure decreases, increasing the production rate and gas velocity throughout the wellbore and the required critical rate to remove liquids decreases because of the reduced pressures. Systems Nodal Analysis tools are ideally suited to analyze the effects of reducing the surface tubing pressure with compression. Several compressor types are used to lower the pressure on entire fields of gas wells or to lower the pressure on individual gas wells. For single-well applications, the different types of compressors used are rotary lobe, re-injected rotary lobe, rotary valve, liquid ring, liquid injected rotary screw, reciprocating, screw, and sliding vane. Gas jet compressors, or eductors, are classified as thermocompressors and are in the same family as jet pumps, sand blasters, and air ejectors.