This new perforating technology has a track record of performing successfully in every instance that it was used to establish an injection rate when its application did not follow a failed treatment. (Image courtesy of Advanced Propellants)

Fracture stimulation can be risky, especially under certain conditions. And some fracturing technologies such as blast-enhanced fracturing, pneumatic fracturing, and hydrafracturing have drawbacks. Many companies using alternative propellants to fracture wells face problems of compatibility with wellbore fluids, fluids causing unpredictable flame spread, and random ignition. It was obstacles such as these that prompted the Advanced Propellants division to rethink wellbore stimulation.

One particular obstacle the company has addressed is the inability to hydraulically fracture wells where there is close water contact. In the case of the wells in question, stimulation using a hydraulic method would likely cause fractures into the water zone. The biggest challenge, in this case, was predictability.

Propellant has to be in fluid to focus the gas generated; however, if fluid is allowed to soak into the propellant, an unpredictable flame spread can occur. Typical events last less than one second. Without a predictable flame spread in such a short timeframe, the variance is great. And if fluid contacts the oxidizer in the propellant, the oxidizer is dissolved, and the propellant fails.

A new type of propellant was developed out of necessity. X-Tend-A-Perf is a patent-pending system that delivers the power of rocket fuel with a scientifically designed ignition system that allows accurate prediction, control, and measurement of the effects of each targeted stimulation event.

How it works

This new approach includes an ignition system, firing train, and a process that uses a fluoroelastomer coating to protect the propellant from wellbore fluids. By creating a controlled burn instead of an explosion, more pressure can be harnessed, which results in a larger perforation and increased flow near the wellbore area. This method is particularly effective in situations with close water contact, multiple open intervals, transitional stress well bores, fluid sensitive formations, and skin-damaged perforations.

Another advantage of this means of fracturing is that it is simple to deploy. The new technology allows predictable event and pressure to be repeated, and pressure can be varied by exposing more or less surface area of the propellant. This is possible because the ignition system is controlled by a number of splits on the stainless-steel tube. By controlling the surface area and not allowing the wellbore fluid to soak into the propellant, it is possible to fracture and increase the radial flow area near the well bore every time.

In the field

X-Tend-A-Perf is hitting its mark in the field. There have been many documented cases of successful results in terms of time savings, improved safety, and increased production. Pressures in disposal well pumps have been lowered as much as 1,000 psi after being treated with the propellant. Several wells that could not be hydraulically fractured because of close water contact produced at commercial rates following treatment. The new technology also broke down horizontal formations that could not be pumped into at 10,000 psi. After treatment, the formations broke between 5,300 psi and 8,200 psi.

X-Tend-A-Perf is energetic and long burning for an extended treatment and has a unique initiation process and patented coating process to ensure predictability. Its variable surface-area ignition increases or decreases the release of gas as needed.

This new technology holds promise in:
• Opening multiple fractures in disposal or injection wells;
• Delivering higher pressure to initiate a hydraulic fracture;
• Avoiding contact with close water zones;
• Cleaning precipitants that are clogging the near wellbore space;
• Cleaning the well bore without putting stress on and damaging the tubular;
• Shooting through multiple casing strings;
• Treating well bores containing multiple open zones without packing off each zone; and
• Making production evaluations to see if further work is justified.

Successes

A report issued on a disposal well operated by Winchester Production Co. in North Louisiana outlines the application of this technology. In this case, a pump-in pressure before using X-Tend-A-Perf was 1 bbl/min at 1,400 psi. After using the propellant treatment, the pump pressure changed to 1 bbl/min at 550 psi.

In another disposal well in DeSoto Parish, a pump-in pressure of 2 bbl/min at 1,700 psi was used. Three zones were treated, resulting in a pump-in pressure change to 5 bbl/min at 420 psi.

In a third report, a company working in the Cotton Valley Sand area in North Louisiana almost hit a brick wall. The formation could not be broken at 5,800 psi, even using an acid treatment. After two treatments with X-Tend-A-Perf, the well broke at 3,520 psi.

In the Brazos block in the Gulf of Mexico, a well showed skin damage over 100 ft (30.5 m) of perforations in a 3.5-ft (1 m) liner pattern. Prior to treating this well, production was at 8.2 MMcf. After spacing out the propellant in three separate runs, the well produced at 14.1 MMcf.

In a close water contact situation in five Travis Peak wells in Panola County, Texas, the wells were 6,000 to 7,500 ft (1,829 to 2,286 m) from water, and permeability was between 0.5 md and 5 md. In this case, a hydraulic fracture is usually needed for a well to produce at commercial levels. After perforating, very little pressure was seen.

Pressure began to increase instantly once the propellant was applied.

In a multizone fractured well in Utah, production came to a standstill until X-Tend-A-Perf was used. The well was very tight and had to be fractured and sand propped.

After a few days, the well was producing at 300,000 cf/d. A hole then developed in the casing, exposing the five producing zones to a noncompatible fluid, causing production to fall to zero. Even with the damaged casing repaired, production could not be re-established. After all five zones were treated with X-Tend-A-Perf, the well again began producing at 300,000 cf/d, with fluids still unloading.

Fracturing obstacles

This new perforating technology has a track record of performing successfully in every instance that it was used to establish an injection rate when its application did not follow a failed treatment.

In the Horizontal Cotton Valley Sand area in East Texas, extremely high pressures were required to break formations — when attempts were successful at all. After another propellant technology was applied, improvement was seen in some stages, but there was a success rate of less than 60% in establishing an injection rate or breaking the formation.

The operator chose to apply X-Tend-A-Perf following the initial treatment, but the new approach failed to break the formation at 9,800 psi. A possible reason for this failure is the explosive nature of the competitor’s technology, which rubblized the formation.

However, when the company came up a lateral channel in the same zone and shot new perforations using this new technology, the well broke at 8,300 psi. Three other stages broke at this same pressure, with a final zone braking at 5,300 psi.

This novel perforating technology provides the industry with a new option. Despite its volatile components, it can be used predictably, safely, and reliably.
As operators face new challenges in the field, this technology is helping them to anticipate and face those challenges to operate efficiently and maximize production.