The carbon rod DFO intervention system can withstand the pressures and flow rates of bullheaded stimulation treatments pumped into a well through a surface flow head or fracturing head. The 15-mm-diameter carbon composite rod can withstand the full range of drag forces and is chemically resistant to, and compatible with, common stimulation treatments such as acid washes and scale inhibitor mixes.
With the rod stationary and extending to (or beyond) the bottom zone designated for treatment, the pumped treatment can be tracked down the well in real time on the DAS display, with delivery to its target zone(s) verified and the information available to the pumping company and operator. Thus, they will know immediately if a repeat treatment is necessary, rather than having to wait and possibly rig up a second time.
The use of this technique for real-time monitoring of fracture treatments in unconventional reservoirs has drawn interest from operators. Permanent fiber-optic cable systems installed over the reservoir have clearly demonstrated the ability to monitor and track the placement of fracturing fluids with DAS.
Such fiber installations must be made either with a sliding-sleeve completion with no need for perforations or with a “plug and perf completion” that uses oriented perforating, a complex and expensive technique, to avoid damaging the fiber. Intervention with the carbon rod eliminates these complications and expenses, and enables real-time monitoring of fracture placement.
A protective saver sleeve needs to be installed through the fracturing head to prevent the potential erosion of the carbon composite rod because of the turbulence and high velocity of the proppant-laden fracturing fluid.
Below the fracturing head, it is recommended that the fracture treatment maintain laminar flow down to the perforation zone or sliding sleeve(s). Erosion tests have confirmed that the carbon rod will have minimal loss of material from the outside-diameter surface, which is acceptable for maintaining integrity and sealing ability while pulling out of the hole.
The carbon rod application of the greatest interest to operators is for chemical fluid diversion in refracturing treatments. Treatments must be delivered to producing zones and not to zones that have failed to produce but remain open and cannot be isolated mechanically. Identification of ineffective diversion during a refracturing treatment will enable quick, on-the-spot adjustments to downhole events.