Gas leak at surface wellhead equipment can contribute to a major incident if not contain immediately. High intervention cost and long lead time for wellhead replacement then required operator to find fast fit for purposes solution to avoid extended loss of production time if well idle due to integrity issue.
The approach was to diagnose and quantify presence of the leak, leak communication path and leak severity by performing positive and negative test at all hanger seal port. Two method of gas imaging detection utilizing Optical Gas Imaging (OGI) and Thermal Imaging (TI) was tested to investigate the leak at gap between casing conductor and wellhead landing support ring. Preliminary study on wellhead completion schematic conclude to have two possible leak paths from 36" conductor annulus; through bottom seal 13 3/8" casing hanger or 13 3/8" annulus through casing hanger top seal. The rectification approach was to treat the leak inside out by injecting proprietary sealant into casing hanger seal to regain sealing capabilities. High performance fiberglass wraps plus metal repair putty applied as second barrier which usually use for pipeline integrity restoration.
Baseline diagnostic and post treatment data was compared to evaluate the treatment performance. Out of 12 casing hanger seal port, 9 port was treated with Pressure Activated Sealant (PAS) and 3 port was treated with Time Activated Sealant (TAS) passing the acceptance criteria well barrier envelope. Proper sealant selection was crucial to treat different leak characteristic and correct injection method was important based on sealant activation mechanism. Ultimately, both gap at conductor was encapsulated using wrap system sealed the leak from outside and passed the soapy test. Thermal imaging for gas detection was not as conclusive as optical gas imaging, however most importantly both of conductor observed to have no leak at the surface.
This paper outline sealant selection type and its activation mechanism used for conductor leak rectification field application. The various consideration during engineering study, diagnostic activities and rectification procedure were highlighted as well as the experiences and lesson learnt during the execution phase.