The goal of modern completion tools is to maximize reservoir productivity efficiently and effectively. A key component to the well completion chain is perforating the wellbore, where clean perforations can ensure quality connectivity between the reservoir and wellbore and help deliver fluid and proppant to their intended targets.

Ineffective perforation systems can lead to damaged equipment, ineffective stimulations and can even pose a risk to wellsite workers. Service companies challenged with solving these issues, along with a host of others, have developed an array of systems that have been deployed worldwide, both onshore and offshore.

Docking gun system

In March 2018, Schlumberger released its Tempo instrumented docking perforating gun system. According to the company, the Tempo system combines a plug-in gun design with real-time advanced downhole measurements, which enables and monitors the well’s dynamic underbalance to create clean perforations that boost reservoir productivity.

According to Schlumberger, the docking components of the gun system streamline the deployment of up to 40 guns for selective initiation to perforate multiple reservoir zones with a maximized explosives payload in a single trip into the well.

“By optimizing the dynamic underbalance in the well to minimize or eliminate perforation damage, customers will benefit from increased hydrocarbon production through better quality perforations providing improved connectivity between the reservoir and the wellbore,” said Djamel Idri, president of wireline for Schlumberger, in a press release.

Badr El Din Petroleum Co. (Bapetco), a joint venture between Shell Egypt and the Egyptian General Petroleum Corp., wanted to improve the efficiency of multizone perforating operations in deep wells in the Western Desert. According to a Schlumberger case study on the operation, Bapetco was challenged with improving the efficiency of the its multizone perforating operations in deep wells. Schlumberger deployed the Tempo system, which features a safety- and efficiency- enhancing plug-in design with integrated measurement capabilities.

According to Schlumberger, the deployment of the Tempo system saved significant operational time by arming perforating guns in less than half the previously required time and conducting early downhole verification of system integrity.

Schlumberger’s Tempo system features a plug-in gun design with real-time downhole measurements that monitor the well’s dynamic underbalance to create clean perforations. (Source: Schlumberger)

Enabling targeted restimulations

Baker Hughes, a GE company (BHGE), developed its OptiStriker straddle packer hydraulic fracturing system, which enables targeted restimulation of individual perforation clusters in existing wells to boost production. According to BHGE, the system features a large inside diameter and two resettable coiled tubing-enabled packers offering a pump rate of 20 bbl/min and a differential pressure rating of 10,000 psi. BHGE reports that these features enable high-rate, high-volume treatments that optimize well restimulations and maximize production.

The OptiStriker system isolates individual clusters to better deliver fluid and proppant, especially to areas that might have been untreated or undertreated during the initial fracturing job. According to BHGE, this target-specific fracturing equipment uses only the amount of fluid and horsepower needed to treat each cluster, which minimizes operational requirements and costs by more than 30% compared to other restimulation techniques.

The OptiStriker can be deployed for restimulation operations, formation diagnostics and minifracs, fluid and gel injection, cased-hole wellbores, and in vertical and horizontal wells.

In a recent deployment of the OptiStriker system, an operator needed to restimulate a series of individual fracture clusters as efficiently as possible across a 1,489-m (4,886-ft) lateral section, BHGE reported in a recent case study. Using an OptiStriker straddle packer system, BHGE delivered controlled treatments to 26 individual clusters in a single trip.

TCP tools

Halliburton’s tubing-conveyed perforating (TCP) technologies enable long intervals to be perforated using large pressure differentials while allowing vertical and horizontal intervention using a variety of perforating technologies, including an electronic firing system (EFS). The TCP system can be deployed in deepwater or onshore applications as well as for harsh environment applications.

A field in Angola featured wells that needed to be completed in a single trip, according to a Halliburton case study. The study reported that traditional firing head initiation pressures exceeded the wellhead tree rating. To overcome firing head pressure initiation challenges and enable offline activities, Halliburton deployed a TCP shoot-and-drop string that incorporated an EFS. The result was that the smart EFS single- trip completion provided the means to move some of the work offline, saving an estimated $800,000 in rig operations.

Halliburton reported that the EFS features an 18-day battery life, auto-release mechanism to drop guns after detonation and also enables offline activities like setting a completion packer, performing slickline runs and providing displacement to lighter fluid.

The case study stated that the displacement with lighter fluid before perforating allows the well to flow without killing it and/or exposing the formation to completion fluids that could damage the formation.

Built-in casing perforations

National Oilwell Varco’s (NOV) i-Frac system offers an alternative to conventional perforating tools that utilize guns and explosive charges and are therefore risky. In an NOV case study, the company stated that conventional perforation methods have a negative effect on near-wellbore permeability and also can lead to mechanical damage.

NOV’s i-Frac system offers built-in casing nozzles that avoid using charges or shocks, therefore avoiding damage to the formation. (Source: NOV)

“The impact stress associated with shaped charges and the outward traveling shockwave weakens the rock matrix, which increases the risk of sand production,” the study reported.

The i-Frac system features built-in casing nozzles that cause no damage to the formation because no charge or shock is imposed to the formation. Additionally, the system’s application helps avoid impacts from underbalanced or overbalanced pressure differential between the wellbore and formation, according to NOV.

The built-in casing system features nozzles that are activated from the surface through deployment of specific activation tools. Once the tool engages with the targeted profile, the nozzles are opened and projected into the wellbore fluid.

“With pressure applied from surface and circulation of cement-dissolving fluid, cement detaches from the casing, breaks and then formation connection is initiated,” the study reported. “Quantity and size of nozzles are engineered as per downhole injection and production design criteria.”

NOV cites that an advantage to utilizing perforations with built-in casing technology is consistency in perforation diameter because nozzles are premanufactured and therefore identical.

“Unlike perforations with shaped charges, there is no development of high-stress compact shell around the tunnel with BIC [built-in casing],” NOV reported in the study. “Fractures can find their natural path through the formation and near-wellbore tortuosity is reduced. More efficient proppant placement and efficient fracture conductivity are ensured.”