Why should you properly anchor your rig?
Stabilization during the simplest rod jobs, Stabilization while working with heavy loads, Stabilization when jarring on stuck pipe. Stabilization during high winds. Stabilization during earthquakes.
Steps to properly stabilizing your rig
1. Installation of tested- certified anchors set at either an API pattern or a pattern that is determined to handle the stresses put on the anchors in the case an API pattern cannot be achieved. ( OSAS has a Program to Calculate Non API Anchor Patterns )
2. Rig Footing- Rig footing is just as important as tying off to certified anchors.
3. Proper tensioning of the guy lines.
To properly stabilize your rig all three steps must be met. Any one of these steps not followed can result in an unstable rig up.
Rig Crew Installed Anchors
These anchors are generally a single helix screw type anchor that is installed by the rig crew using a bar and a cheater bar. In most cases, the anchors are installed no deeper than 3 feet below surface, due to the difficulty installing these anchors. Holding capacity of these anchors is less than 2000 pounds in some cases the anchors star failing while the crew is adding tension to the rig guy lines.
Rig Crew Installed Anchors, Predrilling with Hang Auger
Crews are using a hand auger to pre-drill the anchor holes. The hole is drilled and the crew drops the anchor into the hole and fills the hole with dirt. What is overlooked is by using the auger; the natural compaction of the soil is disturbed. By disturbing the natural compaction of the soil, the anchor holing capacity is severely jeopardized.
Study Involving Rig Crew Installed Anchors
In 1990, a study involving anchor pull tests were performed on approximately 400 hand installed anchors in Texas, Louisiana, and California. It was determined that approximately 80% of all anchors failed at loads under 5000 pounds. Approximately 50% failed at 3000% or less. The minimum recommended anchor holding capacity (with a safety factor of 2) for a 3000 well has been determined to be 12000 pounds with a well to anchor distance of 113 feet to 127 feet. A, more realistic well to anchor distance of 65 feet to 100 feet will require an anchor holding capacity of 19,000 pounds