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Monday, April 30, 2007
The main purpose of perforating a well is to establish good flow communication between the well bore and the reservoir. In addition to being conduits for the inflow of hydrocarbons, perforations provide points of injection for water, gas, acid, proppant-laden gels for hydraulic fracture stimulations, and fluids that carry gravel used to control sand flow in weak or unconsolidated formations.
Conventional Jet Perforating
Shaped-charge (or “jet”) perforating has been commonly employed since the early 1950s. Jet charges evolved from the WWII military bazooka and replaced less powerful bullet perforators and other technologies such as mechanical cutters and hydraulic jets.
Perforations are created in a fraction of a second. The shaped charges employ an explosive cavity effect coupled with a metal liner to maximize penetration. The charges consist of a primer, outer case, high explosive and conical liner connected to a detonating cord (Fig. 1). Once the main explosive is detonated, the liner collapses to form a high-velocity jet of fluidized metal particles that are propelled outward. The perforating event could be described as a “punching action” as opposed to blasting, burning or drilling. This punching effect is achieved by extremely high pressures stemming from impact of the initial portion of the jet traveling at approximately 30,000 ft/sec.
An undesirable side effect of perforating is damage to the formation caused by the enormous jet impact pressure, which propels steel, cement, rock and wellbore fluids into the surrounding formation. The shock effect also damages the rock, pulverizing formation grains and leaving loose debris in the newly created tunnels. Thus, perforating damage consists of a crushed zone around the tunnel and debris inside the tunnels, which individually and collectively can limit both well productivity and injectivity.
The removal of debris and damage from perforations is essential to ensure well success in all but the most prolific reservoirs. This often requires additional and sometimes costly procedures such as pumped treatments (acid stimulation, brine wash, hydraulic fracturing, etc.); use of special downhole cleaning tools (hydro-jetting, etc.); propellants (Stimgun™ technology, StimTube™ tool, etc.); static and dynamic under-balanced drilling and completion procedures; and other post-perforation debris management tools and techniques (filters, magnets, etc.).
Perforation clean-up efforts add cost and operational complexity. The procedures are often ineffective (especially in heterogeneous intervals) and as a consequence can actually reduce asset value.
Mitigating perforating-induced damage has been an important aspect of well completion research for decades. The objective is 100% clean perforation tunnels, regardless of rock quality or wellbore conditions. The elusive perfect perforation would yield 100% flow efficiency, providing greater effective inflow area and reduced flux rate – an important factor in controlling sand production and avoiding well failure. It would deliver a step change in flow performance (both productivity and injectivity) and allow all zones to contribute to the well’s productive flow characteristics, enhancing the inflow or injectivity profile and increasing ultimate reserves recovery.
ConneXSM Perforating
ConneXSM Perforating is a new generation of shaped charge resulting from the combined intensive development effort of GEODynamics, Shell International and QinetiQ. ConneXSM Perforating – a ReActive™ perforating technology – is based on a revolutionary concept created and patented by QinetiQ that is exclusively licensed to GEODynamics. The technology has been developed over the last three years through the substantial financial support of the Shell GameChanger program. Shell GameChanger provides a process to capture, nurture and mature game-changing ideas, until they are ready to be picked up in the mainstream technology development activities.
Upon detonation, this novel groundbreaking perforation solution creates a secondary reaction within the perforation tunnel. The reaction is formed by use of new liner technology, incorporating a carefully controlled combination of bimetallic liner material that is pressed under very specific conditions. The reactive properties of the charge develop high lateral pressures within the perforation tunnels, creating a self-cleaning action that results in open, debris-free holes.
The ConneX™ perforating charge is compatible with existing gun technology and traditional perforating procedures. Companies will not have to change the way they handle, ship or operate perforating equipment. Even the outer case of a ConneX™ perforating charge looks like a traditional shaped charge. With ConneXSM Perforating, GEODynamics has added new functionality to the conventional shaped charge by changing the way it is made and the way it reacts upon detonation.
As previously mentioned, the normal debris found in perforations made with traditional charges consists of pulverized formation material, explosion by-products and remnants of liner material. Some debris can be flushed from the perforation if an effective rate of flow is established. However, in low-permeability formations, in zones that will immediately be fractured, in injection wells that will not be reverse-flushed, and whenever an effective underbalance cannot be established to induce flow, the debris remains trapped in the perforation tunnel. This seriously impairs the perforations’ flow characteristics.
The ConneX™ perforating charge is extremely advantageous in such cases. The event created by the ReActive™ perforating technology results in the expulsion of debris and crushed zone material that would normally remain trapped in the perforation tunnels (Fig. 2). In the case of the
· +44% clear tunnel depth
· +164% tunnel surface area
· +355% tunnel volume
· +35% improvement in flow performance.
Tests conducted during development positively indicate a strongly exothermic, Hume-Rothery intermetallic reaction between liner components, induced by the shock upon detonation. This secondary event occurs within the perforation tunnel in the microseconds after it is formed. The secondary event effectively “cleans” the perforation tunnel of debris and removes crushed material from the tunnel wall, leaving a near-ideal and optimized flow path.
The ConneX™ charge technology, proprietary explosive envelope, and custom liner design were developed over a three-year period by GEODynamics, Shell and QinetiQ engineers.
ConneXSM Perforating Summary
Flow lab tests have demonstrated that this new class of perforator has the following characteristics:
· A secondary reaction is created upon detonation
· Perforating tunnels are effectively “cleaned” and free of both debris and crushed zone
· The ConneX™ perforator does not require underbalanced conditions to clean the perf tunnel
· Positive cleaning effects generated by the ConneX™ perforating technology are relatively insensitive to rock
type or quality
· Perforation tunnels created by the ConneX™ perforating charges exhibit superior flow characteristics that
improve hydrocarbon recovery.
FOR MORE INFORMATION CONTACT:
Matt Bell
Vice President, Technology
GEODynamics, Inc.
Phone: +1 817.341.5363
Email: [email protected]
Joe D. Woods
President
International Pinpoint Co.
Phone: +1 281.556.8866
Email: [email protected]
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