Coaxial Perforating Charge for In-Hole Compacted-Zone Fracturing
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Solution Overview
Problem
Conventional oil well perforation methods create compacted zones that significantly reduce stratum permeability, leading to decreased oil well production capacity, as the energy from perforation fractures is largely consumed within the well casing and shaped charges inevitably form compacted zones around deep holes, damaging rock mechanical properties and fluid flow performance.
Innovation Solution
A coaxial perforating charge comprising a shaped charge and a ring-shaped fracture explosive pack, where the fracture explosive pack is impregnated with ammonium perchlorate, aluminum powder, and dioctyl sebacate, and is coaxially arranged with the shaped charge to self-eliminate compacted zones by inducing sympathetic explosions within the perforated holebore, thereby restoring original stratum permeability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If conventional shaped charge perforation is used, then perforation depth and tunnel formation are improved, but compacted zone is formed around the tunnel which greatly decreases stratum permeability
Solution Approach 1:
The invention divides the single perforation process into two sequential stages: first the shaped charge creates the perforation tunnel, then the fracture explosive pack eliminates the compacted zone. This segmentation allows each component to perform its specific function without interfering with the other, solving the contradiction between tunnel formation and compacted zone creation.
Solution Approach 2:
The invention converts the harmful compacted zone into a beneficial fractured zone by using the compacted zone as a containment structure for the fracture explosive pack. The compacted zone that would normally reduce permeability is instead used to hold the explosive pack in position, and subsequent detonation of the pack transforms the compacted zone into a fractured zone that enhances permeability.
2Strength
If perforation fracture recombiner is used to create pressure within well casing, then fracturing cracks are generated, but most energy is consumed within the well casing causing big energy loss
Solution Approach 1:
The invention extracts the fracture explosive function from the well casing environment and relocates it to the perforation tunnel within the stratum. By placing the fracture explosive pack inside the container at the front end of the shaped charge, the explosive energy is directly applied to the compacted zone rather than being wasted on the well casing, significantly improving energy utilization efficiency.
Solution Approach 2:
The container serves as an intermediary structure that guides the fracture explosive pack to the precise location within the perforation tunnel. This intermediary device ensures that the explosive energy is delivered exactly where needed - into the compacted zone - rather than being dissipated in the well casing, thereby solving the energy loss problem.
3Shape
If conventional jet perforation is used, then perforated tunnel is formed, but compacted zone is inevitably formed around the tunnel which damages mechanical property and fluid flow performance
Solution Approach 1:
The invention performs preliminary action by placing the fracture explosive pack into the container before the perforation operation. The pack is pre-positioned and ready to be deployed into the perforation tunnel immediately after tunnel formation, eliminating the compacted zone while the tunnel structure is still fresh and the compacted zone is most problematic.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The coaxial perforating charge effectively eliminates compacted zones, improving stratum permeability and oil well production by generating a jet that carries the fracture explosive into the perforated tunnel, causing multiple explosions to fracture the compacted zone and restore original permeability, demonstrated by increased oil output and reduced fracture pressure compared to conventional methods.
Implementation Method 1
the shaped charge generates a jet and enters the stratum, so as to form a perforated holebore
Implementation Method 2
a plurality of sympathetic explosions are subsequently induced within the perforated holebore, which generate cracks around the perforated holebore and completely communicates the perforated holebore with the stratum around the perforated holebore
Data Source
AI summary
A coaxial perforating charge includes a shaped charge and a container having a fracture explosive pack inside. The container is coaxially provided at a front end of the shaped charge; the fracture explosive pack is a ring-shaped explosive pack formed by impregnating a fracture explosive for eliminating a compacted zone into the container; the fracture explosive pack is coaxially arranged with the shaped charge. The fracture explosive includes ammonium perchlorate, aluminum powder, additive, and dioctyl sebacate; the additive is hydroxyl-terminated polybutadiene (HTPB), or a mixture of HTPB, N,N′-diphenyl-p-phenylenediamine and toluene di-isocyanate. A perforation method thereof, for self-eliminating a compacted zone, includes steps of: running a jet perforating gun downward; perforating while self-eliminating a compacted zone. The charge and its perforation method are reasonably designed, convenient, safe, reliable, well performed, and able to perforate while self-eliminating the compacted zone, which effectively eliminates an impact on rock permeability of the compacted zone.