?A major factor in the success of well-intervention projects using coiled tubing is the ability to disperse fluid within the wellbore. Halliburton’s Pulsonix TF service, along with DuraKleen, incorporates coiled-tubing and fluidic oscillator technology with tuned frequency capability and asphaltene inhibition to enable fine-tuning rates and frequencies and decreased deposits.
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 intentions when the area of the wellbore that requires the application treatment is the area of the most resistance.
Fluidic oscillation creates alternating bursts of fluid to break up or dislodge near-wellbore damage to restore the flow through perforations and clean the near-wellbore area. The tool is equipped with both side and bottom parts for more direct impingement on perforations. As damaged portions are removed, waves penetrate deeper into the formation for more effective cleaning and stimulation. An entire interval is cleaned.
The tool also reduces communication between perforations and allows for faster operations by using one trip to clean out, fill and stimulate the well. Unlike conventional jetting tools, the Pulsonix TF tool is not limited by standoff requirements, and can be used with other tools.
Recently an operator used the tool and inhibitor 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, increasing daily production by about 500 barrels.
Within a month, however, production declined to about 200 barrels per day. The company then applied the new tuned-frequency service with a larger volume of acid to penetrate an additional foot into the formation, and the asphaltene inhibitor. The second treatment increased the well’s production up to 1,000 barrels per day.
DuraKleen asphaltene inhibitor uses environmentally enhanced water/aromatic solvent emulsions to clean and dissolve asphaltene deposits. In conjunction with tuned-frequency fluid oscillation, the solvency is enhanced by the dispersal effects of the surfactant.
The new solvent offers several important benefits, including a flash point greater than 145? Fahrenheit (63? Celsius). It contains no benzene, ethyl benzene, toluene or xylene. All components are fully miscible, and it may be mixed in batches or on the fly.
It strips asphaltenes and waxes from tubulars as well as formations. Also, the solvent provides a long-lasting treatment by leaving the formation in a water-wet state.
In another case, reservoir pressure decline and resultant asphaltene deposits were severely affecting an operator’s production from an otherwise prolific well. The well was producing from a 6.25-inch, 3,280-foot horizontal hole in a naturally fractured carbonate reservoir at a vertical depth of 10,500 to 12,500 feet. The well produced 30? to 40? gravity oil with an asphaltene content of 0.5% to 0.7%.
Asphaltene agglomerates were plugging the choke several times per day. The resultant fluctuations in pressure and rate caused further damage to the fracture network by accelerating asphaltene deposits. Also, the fluctuations moved the debris along the horizontal section and toward the surface, exacerbating the choke-plugging problem.
The operator cleaned the tubing in an attempt to stabilize the production. This had the opposite effect and the well started to have more problems. Using DuraKleen, bull heading and coiled-tubing placement of 2,200 barrels of cleaning agent, production doubled and treatment life was significantly longer.
Along with the cleaning agent, the system’s 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.
In other well interventions, Pulsonix 200 fluidic oscillation, when used with resin technology, can increase the effectiveness of formation consolidation to help prevent sand production. This type of system uses a solvent/resin mixture to deposit 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 are direct (matrix) injection and pumping through coiled tubing.
The direct (matrix) injection method does not use tools, coiled tubing or any other mechanism for aiding in the placement of the consolidation fluid treatment. The major disadvantage of pumping the treatment through 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 tubing past the interval being treated while fluids are pumped. It also provides the ability to sweep the interval during treatment.
The fluidic-oscillation pulsation creates a radial dispersion of the consolidation material, thereby optimizing the exposure of material to the reservoir, and improves and equalizes the injectivity across variable permeabilities.
Pulsonix 200’s fine-tuned fluidic oscillation pulsing technology is useful in both vertical and horizontal wells and both openhole and cased hole for oil, gas, injection, geothermal, CO2, disposal, monitoring and solution mining.