8 - Liquid unloading using chemicals for wells and pipelines

Abstract

Liquids in gas wells and pipelines in annular flow are removed by movement of the liquid film with the gas along the pipe wall and liquid droplets entrained along the high-velocity core. Physical and chemical conditions can increase or impede the movement of liquid. Chemicals modify fluid properties such as surface tension. In contact with gas, they can create a foam which has a lower density. Chemically modified properties of a fluid can change the relationship between pressure drop and flow. In special instances, the changes can dramatically decrease pressure drop for a given flow rate. For economical treatment with chemicals it is important to identify opportunities when chemical treatment can result in liquid unloading. Chemicals have been used to unload liquids from gas wells, gas storage wells, plunger-lifted gas wells, gas-lifted oil wells and pipelines. Surfactants can be used continuously or intermittently. Capillary injected application have been a popular means to introduce chemicals in wells. In offshore and European wells, special designs were needed to satisfy the challenge of safe pressure containment with continuous injection of chemical. For each application special challenges exist with each application. Testing for fluid and materials compatibility is important for each application. Productive use of chemicals is associated with the intrinsic decline rate of reservoirs. Typically chemical use is most relevant when the reservoir becomes mature. Companies that recognize the shift in maturity of their asset and introduce an appropriate chemical program will increase the ultimate recovery of gas from the reservoir.