Abstract
This paper discusses the successful deployment of Multi-stage Fracturing (MSF) completions, composed of novel expandable steel packers, in high pressure, high temperature (HP/HT) horizontal gas wells. The 5-7/8" horizontal sections of these wells were drilled in high pressure, high temperature gas bearing formations. There were also washed-outs & high "dog-legs" along their wellbores, due to constant geo-steering required to keep the laterals within the hydrocarbon bearing zones. These factors introduced challenges to deploying the conventional MSF completion in these laterals. Due to the delicate nature of their packer elastomers and their susceptibility to degradation at high temperature, these conventional MSF completions could not be run in such hostile down-hole conditions without the risk of damage or getting stuck off-bottom.
This paper describes the deployment of a novel expandable steel packer MSF completion in these tough down-hole conditions. These expandable steel packers could overcome the challenges mentioned above due to the following unique features:
High temperature durability.
Enhanced ruggedness which gave them the ability to be rotated & reciprocated during without risk of damage. Reduced packer outer diameter (OD) of 5.500" as compared to the 5.625" OD of conventional elastomer MSF packers. Enhanced flexibility which enabled them to be deployed in wellbores with high dog-leg severity (DLS).
With the ability to rotate & reciprocate them while running-in-hole (RIH), coupled with their higher annular clearance & tolerance of high temperature, the expandable steel packers were key to overcoming the risk of damaging or getting stuck with the MSF completion while RIH. Also, due to the higher setting pressure of the expandable steel packers when compared to conventional elastomer packers, there was a reduced risk of prematurely setting the packers if high circulating pressure were encountered during deployment. Another notable advantage of these expandable packers is that they provided an optimization opportunity to reduce the number of packers required in the MSF completion. In a conventional MSF completion, two elastomer packers are usually required to ensure optimum zonal isolation between each MSF stage. However, due to their superior sealing capability, only one expandable steel packer is required to ensure good inter-stage isolation. This greatly reduces the number of packers required in the MSF completion, thereby reducing its stiffness & ultimately reducing the probability of getting stuck while RIH.
The results of using these expandable steel packers is the successful deployment of the MSF completions in these harsh down-hole conditions, elimination of non-productive time associated with stuck or damaged MSF completion as well as the safe & cost-effective completion in these critical horizontal gas wells.
High Temperature, High Pressure Devices for Zonal Isolation in Geothermal Wells