Innovative Analytical Team Approach to Restore Integrity of Challenging Wells, Salvage Gas Tower and Used to Eliminate Complex and Costly Gas Well Workover
Authors: El Sayed Mohamed , Al-Suwaidi A. S. , Al Marri Faisal M. , Khalil Hassan Ibrahim , Hussein Mohamed 
Published: February 2011

Collaboration and team work spirit resulted in a very successful to restore the integrity of challenging wells and salvage an important gas tower that worried ADMA- OPCO and Share Holders for long time. One team concept is demonstrating a great success in handling and sorting out large scale problems or high challenging issues.

Tower US-A is an important tower located in the centre of Umm Shaif field. It has two gas producers and three gas injectors (Fig.1). The tower was shut down and secured in 1999 after a gas explosion while cementing the 20" casing of well US- AA. Significant hydrocarbon gas bubbles were observed in the uncontained annulus (20"×30") coupled with high pressures built up in (20"×13 3/8") and (13 3/8"×10 ¾"−9 5/8") annuli in well US- AA. These annuli pressures were close or more than the maximum allowable safe pressures. Moreover, the well US- AB showed high sustained pressure in (7 5/8" × 51/2") production annulus. Such conditions risk ranked both wells number 1; since they are highly dangerous and unsafe that could lead to the loss of tower and production.

Team introduced the following innovative solutions and practices to tackle challenges: Multidiscipline approach to prepare and execute the work plan.Cause Tree Analysis (CTA) to identify root causes of the problems.Isotope analysis to identify the source of the leaking fluids.Innovative safe rate calculations using reservoir and drilling engineering concepts and softwares.High resolution 2D Seismic to identify the presence of shallow gas.The use of Micro fine cement for remedial work.Decision Tree Analysis (DTA) and numerous Risk Assessments to set the final execution plan.Innovative Monitoring Program post remedial and optimizing rig move to the tower.

The source of hydrocarbon gas bubbles was found to be from certain reservoir behind three casings due to poor cementation and damage of the cement in both annuli in well US-AA. On the other-hand, in well US-AB, the problem was due to a leak in the seal assembly.

The recommendations of the multidiscipline team were implemented in 2007. The integrities of both wells were restored by eliminating the gas bubbles flow at surface, annuli pressures of well US-AA and eliminated the production annulus pressure of well US-AB.

Restored tower Integrity, gas production and injection resulted in huge capital saving estimated to be US$ 150 Millions worth of assets in addition to the increase of oil and gas production. Both gas wells can produce 95 MMSCF/D for injection to support some 32000 bopd for 6 years. Most importantly, the elimination of HSE risks associated with discharge of the gas bubbles to atmosphere and high annuli pressures.

The gained experience and the above innovative analytical approach used to resolve similar problems and also eliminated conducting complex and complicated unnecessary gas well workover in year 2010.

Clear and thorough analysis has enabled to capture any failures and allowed better understanding of the problem. Consequently the devised solution has enabled a well consolidated plan to restore the gas wells in an integral state

It has set an excellent example that good results can be achieved through involvement of ADMA-OPCO concerned divisions and management support through a transparent and collaborative process.