Apparatus and method for penetrating oilbearing sandy formations, reducing skin damage and reducing hydrocarbon viscosity

Abstract

A shaped charge and a method of using such to provide for large and effective perforations in oil bearing sandy formations while causing minimal disturbance to the formation porosity is described. This shaped charge uses a low-density liner having a filler material that is enclosed by outer walls made, preferably, of plastic or polyester. The filler material is preferably a powdered metal or a granulated substance, which is left largely unconsolidated. The preferred filler material is aluminum powder, or aluminum particles, that are coated with an oxidizing substance, such as TEFLON®, permitting a secondary detonation reaction inside the formation following jet penetration. The filled liner is also provided with a metal cap to aid penetration of the gun scallops, the surrounding borehole casing and the cement sheath. The metal cap forms the leading portion of the jet, during detonation. The remaining portion of the jet is formed from the low-density filler material, thereby resulting in a more particulated jet. The jet results in less compression around the perforation tunnel and less skin damage to the proximal end of the perforation tunnel.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The invention relates generally to the design of shaped charges. In particular aspects, the invention relates to improved liner design for shaped charges and the use of improved shaped charges within a wellbore in order to better penetrate oil bearing sandy formations with minimal skin damage and to reduce hydrocarbon viscosity. Such a shaped charge features a composite jet that produces a large diameter hole in the formation, barely disturbing the formation properties. Such charges will greatly benefit gravel-packing completions. [0003] 2. Description of the Related Art [0004] Shaped charges are used in wellbore perforating guns. A shaped charge typically consists of an outer housing, an explosive portion shaped as an inverted cone, and a metal liner that retains the explosive portion within the housing. When oil-bearing sands are perforated by conventional shaped charges, the full oil-producing potential of the fo...

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Benefits of technology

[0010] The liner is also provided with a metal cap member for penetration of the gun scallops, intervening well fluid, and the surrounding oilwell casing and cement sheath. The metal cap member forms the leading portion of the jet, during detonation. The remaining portion of the jet is formed from the low-density, unconsolidated powder liner, thereby resulting in a more particulated jet. The jet causes little compression around the perforation tunnel and the skin damage is minimal.

[0012] The present invention provides significant advantages over prior art devices and methods, such as those described in the Liu patent application. In preferred embodiments of the present invention, heating of the aluminum is more assured due to the collapse of air voids present in the unconsolidated aluminum powder. Air void collapse and high temperatures are developed locally in the vicinity of aluminum particulates when the detonation wave resulting from explosive initiation sweeps over the liner. Also, the present invention is not dependent upon aluminum particles finding water or other oxygen-carrying molecules to react with. In preferred embodiments, polytetrafluoroethylene (PTFE) or TEFLON®, a very powerful oxidizer carrying a large number of fluorine atoms, is coated onto the aluminum particles.

Problems solved by technology

This, in turn, releases a high amount of energy by causing a secondary detonation in the perforation tunnel.

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