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

Proper Guy Line Tensioning is an important part of Stabilizing the rig. Since not everyone carries a tensiometer in their back pocket, the API RP4G committee developed a chart that can help in determining if the guy lines are properly Pre-tensioned by measuring sag in the lines vs. line of sight. Click Here To View Chart with recommended Pre-tension loads vs. guy wire sag.

This section is important because anchor loading can be affected by not only anchor spacing but also the depth of the well. Click Here To See Chart , list the calculated anchor loading based on distance from well to anchor and the well depth. The loads listed are based on a 96 foot mast, 120 degree maximum angle between adjacent anchors, Maximum wind load of 15# per square foot ( 70 mph ), 2 7/8” tubing racked back at 20 stands per row with 7/8” and 3/4” rods standing back as well, and Adequate foundation support and adequate crown to carrier internal load lines.

“Z” distance ( Load Side ) should not be less than 60’ from wellhead when anticipated hook load will exceed 50 percent of the maximum allowable hook load.

Anchor spacing directly affects the stabilization of the rig or tower!

When purchasing a new Rig, the rig manufacturer has a plate on either the carrier or the bottom of the mast with recommended Anchor spacing’s which are typically either 180 foot square or 150 foot square. Unfortunately the only areas you are going to find locations big enough to accommodate these patterns are in Texas, Louisiana, and Wyoming to name a few. California along with a handful or so of other states build much smaller drill sites. In Response to this, a committee was formed in the early 1980’s to address the issue of stabilizing the rigs on smaller locations. The committee consisted of Professional Structural Engineers, Oil Industry Representatives, Rig company Representatives to name a few. What was agreed upon between all parties and accepted by the rig manufactures was that on locations that would not accommodate the larger patterns that it would be acceptable to use the API RP4G pattern if the anchors used were installed and tested to meet the stresses of the given pattern. Click Here To See The Pattern

Adequate Foundations are an essential element in providing Stability for Masts, Rig carriers, and substructures. Foundation design should consider safe bearing loads at mast, substructure, and rig carrier support points.

The area around the main support jacks shall be graded, leveled, and maintained so that oil, water, and drilling fluids will drain away from the work area.

Supplemental footing such as rig mats made out of timber or steel shall be used to distribute the concentrated loads from the mast to rig support points.

The rig manufacturer load distribution diagram will indicate these locations.

Wellhead Cellars

Wellhead cellars at a well location may present special considerations for safe operations of a portable mast.

Earthen cellars have the potential for cave in. They also fill with rain water, wellbore fluids, and other fluids that can seep into the ground under the mast supplemental footing and reduce safe bearing capacity of the soil. Cellars lined with timbers have the same seepage potential. Large concrete cellars may require a qualified person to inspect the integrity and large steel beams to span the cellar in order to provide the suitable mast support.