Gas-storage wells experience gas deliverability decline over the lifetime of the well for a variety of reasons, but most often decline is caused by near-wellbore skin damage. Recent developments in diagnostic techniques enable operators to identify near-wellbore damage and apply a tailored treatment to reverse the deliverability decline. In a Sayre, Oklahoma gas-storage field, gas deliverability was improved 32.5% in 14 wells, using pretreatment damage diagnostic analysis to remove near-wellbore damage with new coiled-tubingconveyed fluid-oscillation treatments.
A fluid-oscillating tool (FOT) is key to the damage-removal technology. The FOT sends out alternating bursts of fluid to create pulsating pressure waves within the wellbore and formation fluids. These pressure waves help break up near-wellbore damage and restore effective permeability by carrying the fluid past the wellbore into the formation. These oscillating pressure waves are not affected by standoff, which is common with conventional jetting or velocity tools. Kinetic energy in the pressure pulse travels through the wellbore fluid with no appreciable energy loss. The pressure waves expand spherically, providing 360° coverage as the tool is moved through the interval. As damage is removed, the waves penetrate deeper into the formation.
This paper presents a technical description of the processes incorporated to remediate damage in the Sayre field and the technology used in the oscillation treatments. A case study from West Virginia is also presented. Both cases illustrate pretreatment planning, job design, application procedures, and results.