Innovative Capillary Deliquification Safety System Resolves Liquid Loading Problems With a Cost-Effective Solution that Maximizes Production While Maintaining Well-Safety Requirements

摘要

Many mature gas wells worldwide have had to be shut-in due to water loading in the production string, which occurs when the liquid’s hydrostatic column pressure equals that of the reservoir pressure, stopping production. Periodically injecting surfactant chemicals from surface has been tried but is only a temporary solution. Continuos injection of a downhole foaming agent can be used to lift the water and restore gas production. If an injection line is not part of the completion string, an external injection line can be installed either with a rig workover or a rigless through-tubing installation. The first solution requires significant rig expense, and the second can cause loss of downhole safety-valve functionality. A more cost-effective, safer problem resolution method was needed. This paper describes the first ENI field trial of a Capillary Deliquification Safety System that can be retrofitted into existing wells with rigless intervention to quickly reinstate production. This method maintains safety valve functionality and eliminates an expensive well workover. The installation equipment includes a modified wireline-retrievable surface-controlled sub-surface safety valve (WR-SCSSV) with capillary tubing attached below. The injection method operates via the control system for the WR-SCSSV. The installation, which uses the existing control line of the safety valve to inject chemicals, does not require wellhead modification. The trial installation of the new system took place in a shut-in well in a Barbara offshore field in the Adriatic Sea. The trial showed that the system could provide a cost-effective alternative to well workovers and occasional surfactant treatments and will significantly increase hydrocarbon recovery from the reservoir while maintaining the well’s safety level.