How to Cut P&A Costs by 50% with No-Access Ranging

Plug and abandonment is rarely the glamorous part of a well's life, but it is increasingly the expensive one. On complex and legacy wells, no-access ranging-while-drilling can cut rig time by half or more. Here is where the savings actually come from.

The hidden cost of conventional P&A

Conventional P&A on a complex well is concentric: you enter from the top, pull every tubular that isn't permanently affixed, the rods, the pump, anything sitting in the casing, work all the way to the bottom, and fill the well with cement. It has nothing to do with wireline or ranging.

The trouble starts at an immovable object, a stuck fish, a packer, a wireline tool lost in the hole. You can spend days or weeks fighting what can't be cleared and still never finish, and you would often have been better off drilling a relief well from the start. But a relief-well-style P&A has its own cost: because you have to mill and re-enter with wireline, you trip in and out of the hole 15 to 20 times, so it is just as expensive because it takes so long.

Each round-trip is hours of rig clock at full day-rate, plus the risk premium of an open hole. Multiply that across a multi-well campaign and the economics balloon.

What ranging changes

Ranging-based P&A reframes the problem. Instead of fighting back into a damaged wellbore from surface, Gunnar drills a precise new path that intercepts the target casing underground, then places a permanent cement plug on the inside. For a problematic well with an immovable object, ranging-while-drilling is often the most economical option of all: rather than fight the obstruction, you simply drill around it.

Where the 50% comes from

Three things drive the reduction. First, eliminating wireline round-trips removes the single largest block of sequential rig time. Second, ranging-while-drilling keeps the bit on bottom, collecting data as you drill instead of tripping for wireline, and because the ranging tool is encapsulated in the BHA it avoids the open-hole stuck-in-hole risk that every wireline run carries. Third, hitting the target first time avoids the rework that quietly doubles budgets.

Compact systems extend the advantage. Gunnar's 3.5-inch CTRWD™ deploys on coiled tubing, fully encapsulated and able to work under pressure, reaching tight, urban and live wells where a conventional rig is impractical, turning jobs that were bespoke and slow into repeatable ones.

Proof in the field

In Los Angeles, Gunnar permanently plugged an urban oil well that conventional access couldn't reach, securing CalGEM certification and unlocking land now slated for affordable housing. The same ranging-led approach scales to offshore decommissioning, where rig time is far more expensive and the savings compound.