Liners with Bulk Metallic Glass/High Entropy Alloy, Degradable in Formation Fluids for a Skin Free, Clear, Perforating Tunnel, Enabling Enhanced Reservoir Connectivity

A shaped charge for wellbore perforation includes a solid metal or powder liner pressed onto a case, sandwiching high explosives which may have varying thermal stability, dictated by the expected time of exposure and bottom hole temperature (BHT). It is common knowledge that post detonation, the liner-jet punctures the gun body and casing, continuing forward to perforate the formation until its eventual collapse. The jet debris is deposited on the crushed zone forming an impermeable skin and a slug at the end of the perforation-tunnel. This reduces fracture conductivity, and thus, production. Here we present a game changing innovation, the development of a shaped charge with a novel responsive liner. The jet created from our novel degradable liner, post detonation punctures the casing and progress to penetrate the formation until an eventual collapse. However, this system is designed so that, during detonation, a water disintegrable reaction product, bulk metallic glasses (BMG) and/or high entropy alloys (HEA), are formed. These degradable BMG/HEA or complexions decorate the grain boundaries and domain interfaces of the impermeable skin lining the crushed zone of the perforation tunnel as amorphous intergranular films (AIFs) and plug at end of the pathway. Interacting with flowback fluids the BMG/HEA promotes grain dropping, disintegrating the liner and carrot leaving behind a clean perforation tunnel, improving fracture conductivity thus enhanced productivity. In addition, a clear perf tunnel has zero skin value. As such, compared to a coated tunnel with gun and charge debris, it needs little or no acid to clean-up. This results in a demarked reduction of formation breakdown pressures with improved economics for the client. Last but not least this leads to cost reduction of authorized field expenditure (AFE) to support optimized performance of completion design allowing for increased production. CLEAR shaped charges have been qualified to customer specifications in field conditions and are ready to be commercialized. An extension of this technology is being applied to design charges for "Big-Hole" perforations, for the Plug and Abandonment (P&A) market where an effective cement squeeze, anchoring a plug effectively seals the wellbore, preventing the leakage of residual hydrocarbon and associated contamination and emissions.

Comparison of Crushed-Zone Skin Factor for Cased and Perforated Wells Calculated with and without including a Tip-Crushed Zone Effect

A number of different factors can affect flow performance in perforated completions, such as perforation density, perforation damage, and tunnel geometry. In perforation damage, any compaction at the perforation tunnels will lead to reduced permeability, more significant pressure drop, and lower productivity of the reservoir. The reduced permeability of the crushed zone around the perforation can be formulated as a crushed-zone skin factor. For reservoir flow, earlier research studies show how crushed (compacted) zones cause heightened resistance in radially converging vertical and horizontal flow entering perforations. However, the effects related to crushed zones on the total skin factor are still a moot point, especially for horizontal flows in perforations. Therefore, the present study will look into the varied effects occurring in the crushed zone in relation to the vertical and horizontal flows. The experimental test was carried out using a geotechnical radial flow set-up to measure the differential pressure in the perforation tunnel with a crushed zone. Computational fluid dynamics (CFD) software was used for simulating pressure gradient in a cylindrical perforation tunnel. The single-phase water was radially injected into the core sample with the same flow boundary conditions in the experimental and numerical procedures. In this work, two crushed zone configuration scenarios were applied in conjunction with different perforation parameters, perforation length, crushed zone radius, and crushed zone permeability. In the initial scenario, the crushed zone is assumed to be located at the perforation tunnel’s side only, while in the second scenario, the crushed zone is assumed to be located at a side and the tip of perforation (a tip-crushed zone). The simulated results indicate a good comparison with regard to the two scenarios’ pressure gradients. Furthermore, the simulations’ comparison reveals another pressure drop caused by the tip crushed zone related to the horizontal or plane flow in the perforations. The differences between the two simulations’ results show that currently available models for estimating the skin factor for vertical perforated completions need to be improved based on which of the two cases is closer to reality. This study has presented a better understanding of crushed zone characteristics by employing a different approach to the composition and shape of the crushed zone and permeability reduction levels for the crushed zone in the axial direction of the perforation.

The Effects of Confining Stress on Rock Fragmentation by TBM Disc Cutters

In this paper, General Particle Dynamics (GPD3D) is developed to simulate rock fragmentation by TBM disc cutters under different confining stress. The processes of rock fragmentation without confining pressure by one disc cutter and two disc cutters are investigated using GPD3D. The crushed zone, initiation and propagation of cracks, and the chipping of rocks obtained from the proposed method are in good agreement with those obtained from the previous experimental and numerical results. The effects of different confining pressure on rock fragmentation are investigated using GPD3D. It is found that the crack initiation forces significantly increase as the confining stress increases, while the maximum angle of cracks decreases as the confining stress increases. The numerical results obtained from the proposed method agree well with those in previous indentation tests. Moreover, the effects of equivalent confining stress on rock fragmentation are studied using GPD3D, and it is found that rock fragmentation becomes easier when the equivalent confining stress is equal to 15MPa.