New Hybrid System Brings the Flexibility of Coiled Tubing to Long, Extended-Reach Wells

Abstract

The number of long, extended-reach wells being drilled in the oil and gas industry continues to increase. These wells present complex challenges in completion and intervention procedures because operators demand the same level of performance achieved on shallower wells while providing a cost-effective and safe solution.To reach deep target depths with coiled tubing (CT), smaller coil must be used because of reel capacity, which limits pumping rates because of pressure and velocity limitations. Many areas have road weight restrictions that will also dictate the size and length of CT that can be used. As an alternative, jointed pipe can be used; however, using jointed pipe reduces the overall efficiency of the process, as continuous pumping cannot be achieved.The new hybrid system uses both CT and jointed pipe in a single workstring. The system incorporates a unique flapper safety valve that enables seamless functioning of the string in a live well. The hybrid system enables larger CT and jointed pipe to be deployed, which results in higher pumping rates and depths. This reduces the overall job time, while improving safety and efficiency for deeper well applications, including multizone stimulation, cleanouts, drilling, and mill-outs. This paper presents the hybrid system design and benefits in multizone stimulation, drillouts, cleanouts, and other wellintervention applications. Also included is a case history to demonstrate the success of the system when applied in a multizone fracture-stimulation treatment. IntroductionCT is a vital tool for oil and gas operators to achieve safe, efficient, and effective well-intervention operations. Typically ranging beyond 25,000 ft in length and from 1 to 2.875 in. in outside diameter (OD), these continuous strings of pipe are uncoiled into live wells to perform milling, drilling, cementing, logging, perforating, fracturing, completion, or maintenance operations. Deeper well completions with extended-reach horizontal laterals have presented some unique problems to those seeking to perform well-intervention operations.

New Hydraulic-Fracturing Process Enables a Low-Risk, Operationally Efficient Solution While Maximizing Stimulation Effectiveness in Unconventional Reservoirs

“…Time between treatment stages was as low as 40 min, compared to 4 hr typically seen using the plug-and-perforate method. CTFDM process required less than half of the HHP used on conventional jobs in the area The standard CT reel capacity would not support the size and length of CT required; therefore, a new hybrid system (McNeil et al 2011) was used to enable the optimum treatment to be pumped.…”

Coiled Tubing and Jointed Tubing Hybrid-String Well Intervention: Design, Testing, and Case History

“…Some of the benefits of hybrid string include • Extended reach in horizontal wells • Capability to use large CT with higher flow rates • A reduction in horsepower of 30 to 50% for hydraulic fracturing and stimulation (McNeil et al 2011) • Higher cleanout efficiency with the capability of continuous forward and reverse circulation • Smaller and lighter equipment footprint • More weight at the end of string for plug millouts, sidetracks, and long multilaterals • Faster operation compared to JT-only operations • Fracturing through the completion string saves time and money • Hang-off completion string at the end of the job • Fit-for-purpose equipment and tools offers unmatched job safety and efficiency (Ehtesham et al 2011)…”

“…This allows for faster movement between treatment stages and saves 30 to 45 minutes per stage compared to JT-only operations (McNeil et al 2011). Horizontal wells are becoming more common in shale plays because fracture intensity is more important to produce hydrocarbons from them.…”