Underbalanced Perforation Research Articles

Leveraging Coiled Tubing Conveyance in an Integrated and Rigless Abandonment and Perforation Workflow

Summary In Ecuador, shutoff of an underperforming interval through plug and abandonment (P&A) and perforation of a new interval are traditionally completed with a combination of wireline (WL) and tubing conveyance. An alternative method using enhanced coiled tubing (CT) is presented here; it enables a rigless and efficient workflow that leverages real-time downhole data for on-the-fly optimization. The new workflow relies on CT-conveyed technologies without requiring any additional conveyance methods. CT delivered four different services to start the abandonment by anchoring a 7-in. cast-iron bridge plug (CIBP), complete the abandonment with a low-viscosity cement plug, simulate wellbore dynamics during nitrogen pumping to generate the required underbalanced conditions for perforating, and perforate with a 40-ft ballistic payload of 4 1/2-in. guns. Coupled with real-time downhole telemetry, the enhanced CT workflow provided critical downhole conditions, including fluid levels, accurate depth placement and control, bridge plug setting confirmation, underbalanced conditions, perforating head activation and detonation, and postperforation inflow monitoring. Compared with traditional methods, the enhanced CT workflow introduces several benefits toward completing P&A of old intervals and perforation of new ones. These benefits include enabling a rigless workover (WO) intervention, eliminating the need and cost of a WO rig, reducing operational duration by 13%, and potentially reducing asset footprint and field crews by 95 and 70%, respectively. Elimination of a WO rig reduces environmental impact and the number of personnel on location (i.e., risk). The workflow also extends the reach and efficiency of the service in horizontal wells, enables underbalanced perforation, and delivers actionable real-time downhole data. These data elevate traditional P&A workflows and create a step change in efficiency. First, they allow tracking key downhole parameters that help guarantee a reliable operation of each of the tools and services. Second, they provide insights into the actual downhole conditions throughout the intervention to enable the operator and the field crews to make on-the-fly decisions to deliver a safe and optimal service. Those decisions may include fine-tuning the prescribed treatment or extending the scope of the intervention by leveraging the CT’s pump-through capabilities to maximize well performance and meet, or exceed, the operator’s objectives. The innovative combination of real-time telemetry with abandonment and perforating technologies proved a step change in operational efficiency and range, fueled by the quantity and quality of data recorded during the operation. This case study also marks the first documented perforation with 4 1/2-in. guns with fiber-optic real-time downhole telemetry. Furthermore, the integrated, rigless solution provides operators with an opportunity to extend their WO activity pipeline and free up their WO fleet for other activities.

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

Underbalanced perforation can substantially reduce formation damage and improve the efficiency of production operation. The field in question is a giant oil field in Southwest Iran, with over 350,000 bbl/day production rates. Reservoir X is the main reservoir of the field and includes 139 horizontal wells out of the total of 185 production wells drilled in the field. Despite its technical difficulties, under-balance perforation has been proven to result in high productivity ratios and has been shown to reduce workover costs if appropriately conducted. Therefore, this study investigated a customized underbalanced tubing conveyed perforation to enhance oil production. First, post-drilling formation damage was estimated using Perforating Completion Solution Kits. Next, high-density guns (types 73 and 127) with high melting explosives were selected based on the reservoir and well specifications. angles of 60◦ and 90◦ , shot densities of 16 and 20 shots per meter, perforation diameters of By conducting a sensitivity analysis using schlumberger perforating analyzer program, shot 8 and 10 mm, and helix hole distribution were selected as optimized perforation parameters and resulted in productivity ratios up to 1.18. The current study provides a case study of applying a combination of two previously proven technologies, tubing convoyed and underbalanced perforation, in Iran’s giant oilfield. The method used and the outcome could be used to analyze the efficiency of applying the technology in other green or mature fields. Cited as: Mohammadian, E., Dastgerdi, M. E., Manshad, A. K., Mohammadi, A. H., Liu, B., Iglauer, S., Keshavarz, A. Application of underbalanced tubing conveyed perforation in horizontal wells: A case study of perforation optimization in a giant oil field in Southwest Iran. Advances in Geo-Energy Research, 2022, 6(4): 296-305. https://doi.org/10.46690/ager.2022.04.04

Underbalanced Perforation Characteristics as Affected by Differential Pressure

Summary Underbalanced, tubing-conveyed completions are increasing because of the apparent advantages of cleaner perforations, reduced completion times, and stimulation treatments. Radial-flow Berea sandstone core specimens are used to determine the perforation characteristics resulting from time-dependent pressure differentials between core pressure and wellbore pressure during the completion process. The primary perforation characteristic studied [radial flow ratio (RFR)] is defined as the ratio of the perforated flow rate to the flow rate of the unperforated core. The perforation flow tests included pressure differentials from 500 psi [3450 kPa] overbalanced to 1,000 psi [6900 kPa] underbalanced, with immediate or delayed surging. The RFR was affected most by the 500-psi and 1,000-psi [3450- and 6900-kPa] underbalance. The surged RFR's were from 50 to 58% greater than the no-surge RFR's. Perforation hole volumes were increased as much as 55% by the surge, indicating some elimination of the compacted, damaged-zone material. Underbalanced surge conditions (1,000 psi [6900 kPa]) increased hole volume to four times that resulting from 500 psi [3450 kPa] overbalanced, no-surge conditions. Underbalanced surging, either at the instant of perforation or subsequently, appears to improve the flow characteristics of shaped-charge perforations by simultaneously reducing the thickness of the low-permeability crushed zone and increasing the perforation surface area.