Other Unconsolidated Formations in Vertical and Inclined Holes

Abstract

ABSTRACT A project to investigate the cement placement process across heavy oil sands was conducted to help explain some of the problems experienced by a major oil company when cementing casing in a field in Canada. These problems were related to poor quality of primary cementing jobs as suggested by cement bond logs. Various factors affecting mud displacement efficiency were examined using a 15 ft long test annulus comprised of three 5 ft formation sections. Conventional cementing equipment and practices were used in the experiments. Following completion of individual tests, the cement was allowed to set and the test section was cut into cross sections to measure displacement efficiency (percentage of mud removed) and visually examine the character of the cement sheath. Factors affecting mud displacement efficiency and preservation of formation integrity examined in the course of this investigation included the following: Effect of drilling fluid filter cake deposition, its prevention, and removal.Influence of pipe movement (rotation/reciprocation) with and without mechanical casing hardware (cable wall cleaners/centralizers).Effects of pipe centralization, hole washouts.Use of spacers/flushes to improve displacement efficiency.Influence of displacement rates on mud removal efficiency.Examination of above factors under deviated hole conditions. Findings resulting from this research investigation are presented, including recommendations to improve cementing results across heavy oil or other soft, unconsolidated formations in both vertical and inclined holes.