New Pulsonix TF tool is equipped with both side and bottom parts for more direct impingement on perforations. (Images courtesy of Halliburton)

A major factor in the success of well intervention projects using coiled tubing (CT) is the ability to disperse fluid within the well bore. Halliburton’s Pulsonix TF service incorporates CT and fluidic oscillator technology with tuned frequency (TF) capability that enables fine tuning rates and frequencies based on the requirements of the application.

The older conventional methods of circulating or injecting fluid through a ported wash tool or jet-oriented wash tool do not provide fluid distribution assurance. The ease of fluid flow to the area of least resistance will override the best of intentions when in fact the area of the well bore that requires the application treatment is the area of the most resistance.

The fluidic oscillator on which the service is based creates alternating bursts of fluid. The pulsating pressure waves created by the bursts of fluid can break up or dislodge many types of near wellbore damage. This helps restore the flow through perforations and clean the near wellbore area. As damaged portions are removed, waves penetrate deeper into the formation for more effective cleaning and stimulation.

The system removes near-wellbore damage rather than breaking through it resulting in cleaning out the entire interval and not just the open sections. The tool also reduces communication between perforations and allows for faster operations by using one trip to clean out fill and stimulate. Unlike conventional jetting tools, the Pulsonix TF tool is not limited by stand off requirements, and it can be used with other tools enabling a versatile approach to well stimulation.

The company’s service also enables a wider range of rates to match bottomhole assembly (BHA) and stronger amplitudes for improved near-wellbore action. In addition, side and bottom ports allow for more direct contact on perforations enabling efficient functioning at lower flow rates.

Fine-tuned fluidic oscillation pulsing technology is useful in both vertical and horizontal wells, both openhole and cased hole including oil, gas, injection, geothermal, CO2, disposal, monitoring and solution mining.

In addition to removing deposits from perforations and screens which may include mud and cement damage, emulsions, drilling damage and paraffins and asphaltenes, the service can also be used to place treatment fluids. In addition, it can be used for primary stimulation of high permeability formations and preparation for gravel packing or fracpacking.

Improved production

The tool was recently used on a declining well in Colombia. Production had decreased due to fines migration and asphaltene deposits. The company had previously treated the well with its original tool used to perform Pulsonix 200 service and production had increased by approximately 500 b/d. Within a month of the treatment, production declined to about 200 b/d. The company then applied its new tuned frequency service with a larger volume of acid to penetrate an additional foot into the formation. The second treatment increased the well’s production up to 1,000 b/d. In addition to an effective treatment, the well was treated with an asphaltene inhibitor applied using the service.

Fluid oscillation challenges asphaltenes

The advantages of tuned frequency fluidic oscillation technology also enhance the company’s DuraKleen service. Provided with CT, this service provides a long-term solution to combat the challenges presented by asphaltenes, the black, carbonaceous components of petroleum which occur in many crude oils in the form of colloidal, suspended, solid particles.

The system uses an environmentally enhanced water/aromatic solvent emulsion that helps to maintain long-term production rates by cleaning and dissolving asphaltene deposits. In conjunction with tuned frequency fluid oscillation, the high solvency is enhanced by the dispersing effects of the surfactant.

Asphaltenes can precipitate out of suspension due to changes in fluid temperature and pressure associated with oil production. These particles adsorbing to the rock or pipe surfaces can create production problems and increase the possibility of mechanical failure. By using the new cleaning agent combined with the improved reach of fine-tuned oscillation this process has provided enhanced production for declining wells with longer-lasting results.

The new solvent offers several important benefits including a flash point greater than 145ºF (63ºC), it contains no BETX (benzene, ethyl benzene, toluene, or xylene), all components are fully miscible and it may be batch mixed or easily mixed on-the-fly. It strips asphaltenes and waxes from tubulars as well as formation. In addition, the solvent provides a longer-lasting treatment by leaving the formation in a water-wet state. This delays re-deposition of asphaltene deposits.

Asphaltenes removed

Reservoir pressure decline and resulting asphaltene deposits were severely impacting an operator’s production from an otherwise prolific well. The well was producing from a 6-1/4-in., 3,280 ft (1,000 m) horizontal hole in a naturally fractured, carbonate reservoir at a vertical depth of 10,500 to 12,500 ft (3,202 to 3,812.5 m). The well produced 30º- to 40º-gravity oil with an asphaltene content of .5 to .7%. Asphaltene agglomerates were causing the choke to be plugged as often as several times per day. The resulting fluctuations in pressure and rate cause further damage to the fracture network by accelerating asphaltene deposition. Also, the fluctuations promote debris movement along the horizontal section and transportation of the debris towards the surface, exacerbating the choke plugging problem.

The tubing was cleaned previously in an attempt to stabilize the production. This had the opposite effect and the well started to have more problems. The company worked with the Operator to assess the well and recommended a treatment using its DuraKleen service. The treatment included both bullheading and CT placement of 2,200 bbl of cleaning agent.

Following completion of the treatment, the CT tools were inspected. The inspection found them to be completely clean with no asphaltene deposits sticking to or deposited on the tool. This strongly indicated similar cleaning of the tubulars. The well started to produce oil immediately and was placed on production with no blockages from debris returning to the surface. Production doubled following the treatment and treatment life was significantly longer than with previous solvent treatments.

Combined with the cleaning agent, the systems fluidic oscillator technology enabled the increase in production by providing more contact with the affected area. Cleaning out the entire interval rather than just the open sections increased treatment life and insured improved production for a longer term.

Enhances placement of formation consolidation material

Formation consolidation is not a new concept and in many applications has proved to be a successful means of providing sand control. SandTrap service provides features that facilitate the successful use of resin consolidation for oil and gas sands requiring sand control. The pulsing created by fluidic oscillation can help increase the effectiveness of this treatment.

This service uses resin technology to consolidate the near-wellbore area to help prevent sand production. The system uses a solvent/resin mixture that deposits a thin film of resin on the formation matrix grains. The resin is internally catalyzed so no post-flush treatments are needed to initiate curing. The consolidated area maintains almost 100% of initial permeability. The most common placement methods used to place the consolidation treatments are direct (matrix) injection and pumping through CT.

The direct (matrix) injection method does not use tools, CT, or any other mechanism for aiding in the placement of the consolidation fluid treatment. The major disadvantage of pumping the treatment through the production tubing is that treating pressures could begin to increase and approach or exceed the fracturing pressure. The use of coiled tubing provides the option of moving the end of the coiled tubing past the interval being treated while fluids are pumped. It also provides an ability to sweep the interval during treatment and tools can be run on CT to improve fluid placement efficiency.

The fluidic oscillation pulsation creates a radial dispersion of the consolidation material optimizing the exposure of material to reservoir. The pulsation effect improves and equalizes the injectivity across variable permeabilities of the formation face.