Perforating con't 4

Wireline Perforating

Wireline (or electric line) is the traditional way to run perforating guns, providing the advantages of real-time depth control and selectivity. Guns can be run either before the completion is run (casing guns) or through the completion (through-tubing guns). Today any type of perforating gun can be run on wireline including strip guns, casing guns, scallop guns, Pivot guns, Enerjet guns, TCP guns, or oriented guns. Many other explosive devices can also be run, including plug and packer setting tools, cutters, backoff bars, and severing tools.

Perforating Gun Systems and Charges

Schlumberger offers capsule and hollow carrier gun systems with a wide variety of perforating charges for every environment as before.

Completion Perforating

Completion perforating enables large, long strings of guns to be installed with the completion and fired with the right completion fluid in place for immediate cleanup and production.

After firing, the guns are normally dropped into the rathole or left connected to the completion, in which case production is through perforated tailpipe. Additional hardware such as automatic drop subs, shock absorbers, valves, and debris subs can be included in the string.

Before Completion Perforating

Perforating guns can be run before the completion to position guns that are larger than the ID of the tubing. In vertical or deviated wells, guns can be hung off in the liner using a MAXR anchor. When the guns are fired, the anchor automatically releases to drop the guns into the rathole.

In a monobore completion, the guns and anchor can also be recovered to the surface. In horizontal wells, guns can be placed in the horizontal section before the upper completion is run by using disconnect devices run below coiled tubing or drillpipe.

Completion Perforating Without Killing the Well

The CWOK process uses underbalance, dynamic underbalance (PURE), or extreme underbalance perforating for clean perforations, then removes the guns without killing the well.

A typical well kill may damage clean perforations unless very carefully designed pills are developed. CWOK includes the following techniques:

• Through tubing perforating (wireline or slickline)
• X-Tools to drop guns into the rathole
• FIV to isolate the reservoir and enable long gun strings to be recovered to surface
• CIRP to connect and disconnect long gun strings under pressure
• GunStack to run and stack guns on anchors

Other techniques include running isolation plugs through the completion in order to recover DST strings, and PerfPac, which allows completion of gravel packs without killing the well.

Slickline Perforating

Slickline can be used for perforating, setting plugs or packers, or cutting tubing. Slickline operations are normally fast and use simple pressure control equipment. Slickline units occupy a small footprint on rigs or platforms and can be transported easily.

The eFire-Slickline firing head is used to fire guns or initiate setting tools. This electronic device is simple to use and has many useful features including full operator control to arm, fire, abort, and rearm if needed.

Coiled Tubing Perforating

Coiled Tubing (CT) provides additional perforating capability and flexibility over other conveyance systems. The rigidity and strength of CT allows enduring greater tensile and compressive forces, which is a major operational advantage when perforating in highly deviated and horizontal wells or with longer gun strings.

CT perforating is ideal for live wells; pressure control techniques are used to run long gun strings and either drop off or retrieve the guns without having to kill the well.

In subsea wells, the subsea lubricator defines the length of gun that can be run. With other wells, the surface riser or surface lubricator valve determines the length of gun. The CIRP deployment system can be used in conjunction with CT to deploy and retrieve guns under pressure.

In depleted wells where drawdown is insufficient, nitrogen can be circulated at convenience to lighten the overall fluid column, increasing the drawdown at the zone of interest. The resulting pressure differential is similar to that produced by gas lift systems.

For accurate depth control, CT wired with integrated electrical cable is run in combination with a casing collar locator and a gamma ray detector. Optional real-time and memory sensors for pressure and temperature are used to monitor the required underbalance.

There are several ways to activate guns run with CT: hydraulic delay firing heads; drop ball firing heads; eFire-CT firing system using circulation rates; or electrically using "stiff-wire" CT, where an electric line cable is run through the CT to enable firing the guns in a similar manner to a wireline job.

Stiff-wire CT allows the use of standard wireline correlation tools. Hydraulic CT allows stimulation fluids to be pumped without the risk of damaging a wireline cable.

An additional specialty gun is the pump-over gun. This gun allows circulation through a special sleeve on the outside of the gun to the bottom of the string. The pump-over gun is used during fracture operations in horizontal wells to save a cleanout trip between fracturing and perforating the next interval.