November 4, 2011
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№ 9 (September 2011)

“Perekryvatel” Helps to Isolate Drilling Trouble Zones

   “Perekryvatel”, a part of “Systema-Servis” group, is the only Russian manufacturer of equipment for local strengthening of walls (OLKS) used to isolate drilling trouble zones. This equipment simplifies borehole routes and reduces the contingency costs, sometimes even helping to prevent the inevitable abandonment.

By Romanov B.M.

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   This technology is known both in Russia and abroad and is widely used by many drilling companies.

   OLKS set includes shaped tubes and tools for their installation.
The main element defining OLKS is the profiled (axially fluted) pipe. “Perekryvatel” manufactures two types of profile pipes: hexagonal and twin-duct-shaped. Twin-duct pipes have the widest market spread as they require lower excess pressure compared to hexagonal-shaped pipes. Also, no pipe expansion after the flaring process means the best adhesion with boring casing or drilled rock. The hexagonal pipes are used when the required diameter of the circle disallows insertion of the pipe perimeter into the twin-duct shape, or when the profiled pipe must carry additional equipment. In addition, no expansion treatment for hexagonal shape pipes ensures better sealability between the profiled pipe and the casing or the drilled rock.

   Given that during the installation process the profiled pipe should be converted into a cylindrical pipe of required diameter, in the process surviving the internal pressure of at least 17 MPa, the pipe manufacturing technology demands specific requirements.

   There are different production technologies for axially fluted pipes.

   Option 1. Profiling is done using special rollers in tube mills. This method can be applied directly during the manufacture of the pipes. The advantage of this method is high production rate and, consequently, low per-item cost. The disadvantage is the difficulty of linking this profile to the cylindrical pipes. Also, this method is inefficient for small production volumes.

   Option 2. Profiling is done by pulling the pipe through a profile die ring. This method is well-developed and requires no special equipment or technology, but here the profile valleys cannot be deeper than the diameter of the pipe cylindrical part. The last condition is unacceptable for OLKS.

   Option 3. Used for getting OLKS-compliant pipe profile. This option is used to produce metallic patches manufactured by technology developed in VNIKRneft Institute. A standard pipe with less-then-required perimeter is used as the pipe shell. The profiling process uses an expander installed in profile-shaping point. Perimeter expansion to the desired size is done in parallel to the profile-shaping process. Highly precise parameters of the end product and relatively simple tools setup mean that no preliminary calibration is needed for pipe welding. Also, with this option there is no need for preliminary preparation of the required-diameter pipe. However, the process creates a significant load formed by composite stress from profile formation and linear deformation, which affects the expander, creating significant friction. This option is impractical if pipe wall thickness is 5 mm and above. The pipe material should have a low yield stress, which may impact such product parameters as collapse resistance to external pressure.

   Option 4. Similar to Option 3 but here the profiling is performed without the internal expander. This technology is used at “Perekryvatel” to manufacture equipment for local strengthening of walls, hole branching equipment and some other products. This technology was developed jointly by TatNIPIneft and UralNITI Institutes and uses the equipment designed and manufactured by the Irkutsk Heavy Engineering Plant. In this technology, the profiling is done by rollers specifically arranged for minimal power consumption. This setup allows profiling of pipes with up to 12 mm wall thickness. Since this profiling method uses non-standard diameter pipe as profiling feedstock, the pipes need reduction or expansion treatment depending on delta between standard and required pipe diameter. A distinctive feature of this technology is that the resulting profile differs from the profile of the forming rollers but is largely dependent on the tools configuration (with nonlinear configuration-size dependence).

   “Perekryvatel” has over 10 years of experience producing profiled pipes. From 2007 to 2010, the company’s work helped to isolate drilling mud loss zones at 151 wells. Technology is applied in the following regions: Tatarstan, Bashkortostan, Komi, Udmurtia, Perm, Krasnoyarsk, Samara, Saratov, Volgograd, Yamal-Nenets Autonomy.

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