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

Abstract

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.

Application of underbalanced tubing conveyed perforation in horizontal wells: A case study of perforation optimization in a giant oil field in Southwest Iran

“…Several perforating parameters control the productivity of the perforated wells; perforation length, perforation diameter, degree of the damage around the perforation tunnels, shot density, and perforation phasing angle (Abobaker et al, 2021). Some of the listed parameters are easy to quantify and control.…”

“…Afterward, the perforation guns are fired to create a controlled entrance of reservoir fluids into the wellbore. This results in better cleaning of the perforations and improving the well's productivity and injectivity (Bale and Satti, 2020), and if completed successfully, minimizes the formation damage near the perforation zone (Abobaker et al, 2021). In UBP, the perforations are immediately back surged; this results in the debris being expelled into the well upon entrance of formation fluids to the wellbore.…”

A new assessment of perforation skin factor for vertical perforated wells in near-wellbore region

“…Additionally, Molina and Tyagi (2015) applied CFD on a near-well model to examine how a perforated gas well performs, looking in particular at various types of completion techniques and how these strategies might have erosive effects at the wellbore. This study is an extension of the works (Zheng, et al 2016;Ahammad, et al 2018Ahammad, et al , 2019Abobaker et al 2021aAbobaker et al , 2021b for investigating single fluid flow occurring in perforated porous substances numerically and experimentally. The researchers' model was able to predict the pressure gradients of petrophysical characteristics within perforation tunnels and the near-wellbore regions.…”

Construction and application of flow pressure drop model of perforated well considering pressure loss of perforation hole

“…1 ), which can determine the difficulty of formation fluid flowing into wellbore. Many scholars have conducted some studies on optimizing perforation parameters 9 – 12 . The optimization of perforation parameters is generally to build a perforation skin coefficient model or a production model of perforating well, which can determine perforation parameters by analyzing the relationship curves between perforation parameters and perforation skin or well production.…”