Rotating Liners During Cementing in the Grand Isle and West Delta Areas, Louisiana
Authors: Landrum W.R. , Porter J.E. , Turner R.D. 
Published: December 2007

Liner rotation during cementing has resulted in more successful primary cement jobs. For more than a year, every liner cemented by Conoco Inc. in the Grand Isle and West Delta areas offshore Louisiana was rotated during cement placement. This resulted in a dramatic reduction in the number of zone isolation squeezes and liner top squeezes. Savings of $140,000/well were achieved if the liner was rotated during cementing. This cost savings was gained as a result of fewer remedial squeeze cementing jobs. This paper presents liner cementing information that details this technique, with emphasis on liner length, depth and hole angle, centralizer and scratcher program, cement and spacer design, and on-site tips for success.

Introduction

Before June 1980, Conoco experienced many completion problems related to poor liner cement jobs in the Grand Isle and West Delta areas. As a result, high costs were incurred for squeeze cementing liner tops and squeeze cementing for zone isolation (or block squeezes). The decision was made to attempt to reduce remedial squeeze costs by improving the primary cement jobs. To this end it was decided to rotate liners during cement placement. Every liner set from June 1980 through Feb. 1982 was rotated. This study examines every liner set by Conoco in the Grand Isle and West Delta areas from Jan. 1980 through Dec. 1982. Rotation was chosen over reciprocation so that the liner would be in position across the zones of interest all the time that the pipe is in motion, thus eliminating one possible problem encountered during reciprocating-i.e., getting stuck high or at the top of a stroke. A study by McLean et al. in 1967 concluded that rotation is better than reciprocation for mud removal. Also, higher fluid velocities relative to the formation or to the pipe aid in improving mud-displacement efficiency. Rotating casing at 15 to 25 rev/min provides more pipe movement relative to annular fluids than reciprocating 20 ft [6.1 m] on a 1-minute cycle. For these reasons, rotation was chosen over reciprocation for this study.

Liner Hanger Description

During the phase of this study in which pipe movement was incorporated into the cementing procedures, a mechanically set, rotating liner hanger was specified. As many variables as possible were held constant during the field study, and this particular tool was chosen for its simplicity and ease of operation. The tool string consisted ofliner cementing head with drillpipe wiper dart in place,drillpipe swivel,kelly,drillpipe,liner setting tool,latch-in liner wiper plug, andmechanically set rotating liner hanger.

All liners were equipped with centralizers and rotating cable wipers, latch-in collar, float collar, and float shoe, except where noted.

Liner Hanger Operation

With the liner about 2 ft [0.6 m] off bottom, the drillpipe is rotated while circulating to condition mud. In all cases, rotation was achieved through the use of the kelly in the rotary table. During the first cementing operation, the speed of rotation was 40 rev/min. In subsequent operations, the liner was rotated at about 16 rev/min. The design of the setting tool is such that, after the first 18 turns at the tool, the slips are free to set by slacking off weight. Next, with 8 in. [0.2 m] of downward movement, a jaw arrangement of the setting tool slips inside the releasing nut so that continued rotation releases the liner. Now the setting/releasing tool is free to be retrieved from the well.

Cement Slurry Design

The cement slurries were similar in each case for the wells studied. The slurry design work proceeded in a methodical progression. Slurry characteristics and set cement properties were enumerated first. Next, the additives that would provide these properties were specified and evaluated for compatibility. Then the cement systems were formulated and tested for fluid rheology, fluid-loss control, thickening time, and compressive strength. Finally, the amounts of each additive were adjusted to achieve the desired slurry properties for the particular well conditions. In general, the cement systems were composed of Class H cement plus 0.75% dispersant plus 0.4 to 0.8% fluid-loss-control additive plus 3% potassium chloride plus 0.25% antifoam agent, plus 0.1 to 0.3% retarder, to be mixed at a density of 16.2 lbm/gal [1941 kg/m3].

JPT

P. 1263^