Salt-free cement-An alternative to collapsed casing in plastic salts

Journal Article · Wed Feb 01 04:00:00 EST 1984 · J. Pet. Technol.; (United States)

DOI:https://doi.org/10.2118/10885-PA· OSTI ID:6868274

Goodwin, K J; Phipps, K

The high incidence (20 to 25%) of collapsed or doglegged casing in the Williston basin led to an investigation of cementing systems and practices employed in that area. The vast majority of the collapse problems are occurring across the Charles formation. The Charles contains numerous salt sections over a 600- to 700-ft (183to 213-m) gross interval. These salt sections exhibit plastic tendencies when exposed to aqueous drilling fluids-i.e., the salt sections flow. Under plastic conditions, the salt sections flow against the casing before the cement sheath can attain sufficient compressive strength to protect the casing. These salt sections can be seen on conventionally cemented casing strings as 100% bonded sections in what otherwise appears to be poorly cemented intervals. The plastic salt exhibits a horizontal stress against the casing equivalent to the overburden stress (about 1 psi/ft (22.6 kPa/m) of depth). The use of high concentrations (20 to 37.2%**) of salt in cement slurries exhibit a retarding effect on thickening time and the rate of compressive strength development. These excessive development times appear to be contributing to the collapse problems defined. Laboratory investigation of salt dissolution rates in cement slurries, at various annular velocities, show that salt-free cement slurries can be placed across the salt sections with final salt concentrations of less than 10% as a result of salt dissolution. This prompted an investigation involving the possible use of salt-free cement slurries, which exhibit controlled thickening times and much faster compressive strength development, across the Charles. To date, the wells that have been cemented in the Williston basin with the salt-free cement systems have shown no incidence of casing collapse, except as listed in the last paragraph under Field Experience.

• Research Organization: C and S Consulting
• OSTI ID: 6868274
• Journal Information: J. Pet. Technol.; (United States), Journal Name: J. Pet. Technol.; (United States) Vol. 36:2; ISSN JPTJA
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020300* -- Petroleum-- Drilling & Production
03 NATURAL GAS
030300 -- Natural Gas-- Drilling
Production
& Processing
BUILDING MATERIALS
CEMENTING
CEMENTS
CHEMICAL COMPOSITION
DISSOLUTION
DRILLING FLUIDS
FAILURES
FLUIDS
MATERIALS
NATURAL GAS WELLS
OIL WELLS
SALTS
TECHNOLOGY UTILIZATION
WELL CASINGS
WELLS