Flushed zone process helps control gas migration in primary cementing

Journal Article · Mon Aug 16 00:00:00 EDT 1993 · Oil and Gas Journal; (United States)

OSTI ID:5323785

Teichrob, R R ^[1]

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1. Husky Oil Operations Ltd., Calgary, Alberta (Canada)

Gas migration during cementing operations can be eliminated with optimal drilling practices and ultra-high filtrate loss drilling fluids or properly designed squeeze fluids. A method based on the flushed zone theory involves squeezing fluid into a potential gas-bearing formation to reduce the permeability to gas near the well bore. The process aims to suppress gas flow long enough for the cement to set. The process is accomplished in the following way: the well is drilled to a predetermined depth and all inhibited drilling fluids in the well are displaced by an appropriate squeeze fluid. The annulus is packed off and pressure is applied down the drill pipe. The volume of squeeze fluid pumped away is monitored, and the flush volume is estimated based on assumed permeability, porosity, and interval height. Once the squeeze fluid volume is pumped away, the remaining fluid is displaced back to surface with the original mud system. Drilling resumes, and the well is drilled to total depth, logged, and then abandoned or cased. As the hydrostatic pressure imposed by liquid cement decreases as a function of gel strength development, the altered permeability of adjacent gas-bearing intervals precludes gas movement into the setting cement. The concept behind the flushed zone theory is basic: the gas is moved radially away from the well bore face, and because the formation's permeability to gas changes, the gas is kept away at least long enough to drill, log, and case the zone. Because the residual effects of reduced permeability to gas are unknown, cement permeability to gas in itself may play an important role in long-term solutions to controlling migrating gases through micro-annuli.

• OSTI ID: 5323785
• Journal Information: Oil and Gas Journal; (United States), Vol. 91:33; ISSN 0030-1388
• Country of Publication: United States
• Language: English

Related Subjects

03 NATURAL GAS
NATURAL GAS WELLS
CEMENTING
WELL COMPLETION
PROCESS CONTROL
ENVIRONMENTAL TRANSPORT
FIELD TESTS
NATURAL GAS
RECOMMENDATIONS
CONTROL
ENERGY SOURCES
FLUIDS
FOSSIL FUELS
FUEL GAS
FUELS
GAS FUELS
GASES
MASS TRANSFER
TESTING
WELLS
030300* - Natural Gas- Drilling
Production
& Processing