NEKKO Offers New Method for Low Impact Perforation

Combined plastic perforation is a technology of non-explosive perforation and treatment of the near-bottomhole zone of pay beds. It was developed by NEKKO company in 2003 and has been in use since then. This technology underwent all procedures required for approvals and received the Russian Federation patents for inventions No. 2249678, No. 2256066, and No. 2247226.

The combined plastic perforator is a cylindrical device which is equipped with two retractable cutting wheels-mills, forming longitudinal slots in the production casing, and two jet nozzles washing out cement behind the casing and adjacent rock. This technology is applicable in production casing strings having diameters of 102 mm, 140 mm, 146 mm, 168 mm and 178 mm, and strength corresponding to steel grades D, K, E (GOST-632-80).

This is considered to be a combined technology, as it combines perforation of the production casing and treatment of the formation bottomhole zone by fluid jets coming from the perforator at high pressure. The perforator's special operational slots,  jet nozzles and circulation valves make it possible both to pump various fluids (process water, process water plus surfactant, oil, hydrochloric acid, mud acid and other liquid chemical compositions) into the well, and also to recover fluid out of the well by swabbing method, flowing production, reverse circulation without replacement of tubing hanger. The perforator can form paired longitudinal slots in the production casing either across the whole thickness of the bed, or selectively in the required intervals of the bed.

Formation of paired slots in the production casing across the whole bed thickness enables involvement of the maximum amount of fluid-conducting channels and fractures of the developed formation, and the consequent realization of maximum production potential of the given productive stratum.

Selective formation of paired slots in the production casing enables a selective impact on the bed in the intervals of highest production interest. Formation of penetration zone in the production casing with washing-out of cavities in the bottomhole formation zone develops the most effective communication between the well and the formation, and consequently creates the best conditions for further realization of activities aimed at improvement of well productivity by chemical treatment, short-time drawdown (swabbing), etc. The combined plastic perforator makes it possible to inject chemical compositions into the bed during bottomhole zone treatment both under pressure through jet nozzles, and in so-called "cone" mode through circulation valves. As a result, it is possible to form a good-quality penetration zone in the production casing, wash out cavities in the bottomhole zone, inject chemical compositions into the formation and remove products of chemical reaction from the bottomhole zone by means of swabbing, and treat several productive horizons in one run of the combined plastic perforator.

At present the NEKKO perforator is designed with an outer diameter of 80 mm on the basis of the latest technical solutions for operations in sidetracks and wells with horizontal sections. This device, having two cutting wheels-mills, can form longitudinal slots 9 mm wide in the production casing. The penetrated area of one running meter of the casing with 102 mm diameter is 180 sq. cm, which is comparable to the area of penetration of 227 shaped charges with bore diameters of 10 mm or to the area of penetration by 70 shaped charges with bore diameters of 18 mm.

The technology of combined plastic perforation has no shock effect on the production casing. This preserves the integrity of the cement behind the casing above and below the perforation interval and enables high-quality perforation of wells with disturbed or poor quality cement behind the casing. High quality of hydrodynamic communication provides ideal conditions for fluid entry to the wellbore or fluid injection into the formation.

When this method is applied prior to hydraulic fracturing, it results in considerably reduced hydraulic friction during proppant pumping. This makes it possible to significantly reduce the risk of "emergency stops" at the wellbore-formation interface.

At present, many oil companies identify serious problems in the technical status of casing strings and quality of cement behind the casing in their development wells and are searching for low impact perforation methods. Application of the combined plastic perforation technology can provide a solution for their problems.

The trend of stable increases in the number of operations indicates good prospects of alternative low impact technologies for well perforation.

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