Customized Insulating Packer Fluid Improves Steam-Injection-Well Integrity
- Jay K. Turner (Baroid Fluids Services) | Ryan Ezell (Halliburton) | Brian Hugh Macmillan (Halliburton Brown & Root Ltd) | Dodie Ezzat (Halliburton Baroid Drilling Fluids)
- Document ID
- Society of Petroleum Engineers
- SPE Annual Technical Conference and Exhibition, 19-22 September, Florence, Italy
- Publication Date
- Document Type
- Conference Paper
- 2010. Society of Petroleum Engineers
- 2.2.2 Perforating, 5.9.2 Geothermal Resources, 1.14 Casing and Cementing, 5.2 Reservoir Fluid Dynamics, 5.4.6 Thermal Methods, 4.2 Pipelines, Flowlines and Risers
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Excessive unsupported casing growth at the surface is a problem which could dramatically affect the integrity of the steam injection wells. This problem was recently encountered in a Middle East oil field where severe cement fallback on numerous wells caused excessive casing growth upon injecting steam. Surface steam supply lines could accommodate up to 4 ft (1.2 meters) of casing growth, but the wells with poor cement bond experienced up to 8 ft of wellhead movement. Remedial cement placement was not an acceptable option for injection wells that require perforated casing. An alternative economical method to control casing growth was therefore needed.
Fresh water was normally placed in the annulus, which evaporated and released to the atmosphere due to the very high steam temperature (ca. 575°F/300°C). Heat transfer to the casing was very high, causing the excessive casing expansion. Controlling this heat transfer will limit wellhead movement while retaining the energy in the steam for more efficient reservoir heating and oil recovery.
A high temperature insulating fluid was custom-designed for these subject wells. The solids-free water-based fluid had low inherent heat transfer and was gelled with a unique stable inorganic viscosifier to prevent convection at the target temperature. Preventing convection is a key factor in reducing heat transfer. After four days of steam injection, the operator reported that wellhead movement was half of that in offset wells completed with fresh water as the packer fluid. This paper will present and discuss the lab and field data for the new insulating fluid which offers several advantages in reliability and performance for extreme temperature applications such as the geothermal and steam injection wells.
Oil fields with heavy oil reserves require special methods to enhance the recovery of those reserves. Steam injection is a common method, with injection wells properly placed around the production wells. The injected high-temperature steam heats the reservoir rock, facilitating the flow of the viscous oil to the production well. The ratio of steaming wells to production wells varies dependent upon the properties of the oil and the field layout.
A typical steam injection well in the subject field is approximately 3000 ft (910 m) deep. The well is completed with a cemented and perforated 7 in. liner and a 3.5 in. injection tubing string. The 7 in. casing is cemented to within ca. 950 ft (290 meters) of surface; locating the cement top at this level helps to control casing expansion by facilitating heat flow through the casing into the earth. When the well is injecting steam at 575°F (300°C) the wellhead connected to the steam injection line will rise approximately 4 ft (1.2 meters) above ground level as the seven-inch casing heats up and expands.
Considerable ancillary equipment is required to support the injection program and the design of the support systems is based on known and assumed parameters. One of these is the expansion of the production casing, and the steam flow lines supplying steam to each well are designed to compensate for up to about five feet of casing growth. A problem arises when the seven-inch casing is not well cemented; the result is considerably greater casing growth at surface, in some cases up to 9 ft (2.7 meters). Solutions for excessive casing growth included limiting the steam injection rate which significantly reduced the production, or retreating the casing and re-completing the well. Remedial cementing to bring the cement close to surface is not an option in order to maintain the casing integrity by avoiding perforating the casing and squeezing cement.
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