New Barnett Shale Horizontal Completion Lowers Cost and Improves Efficiency

Abstract

Abstract Over the last few years horizontal completions of the Barnett Shale have advanced in an attempt to better stimulate the entire horizontal interval. One standard completion process, where the horizontal is cased and cemented, has emerged. Completing the well consists of running and setting a composite plug on coiled tubing (CT), perforating, stimulating, flowing the well back and repeating the process for the required number of stages for the well. This process is very costly and time consuming, with the added risks of having to remove the composite plugs, plus there is no viable method for re-stimulating these wells at a later date. For over three years now, a new completion system has been deployed in the Barnett Shale that is fast, efficient, less costly and provides equal to or better production than what the standard completion system offers. Using specially designed mechanical open hole packers run on the production liner, mechanical diversion in the open hole section can be accomplished at predetermined points. This provides well site flexibility in completion design, so the fracturing and stimulation process can be optimized. Each stage in the horizontal section can have a specifically designed fracturing or stimulation procedure. The system has also been designed, to allow all of the fracturing or stimulation treatments to be pumped in one continuous operation with the added benefit of re-stimulating all or selected intervals at a later date if desired. This has proven to be very cost effective and efficient, while reducing the time required to bring production on line. With a multitude of jobs completed to date in the Barnett Shale, this paper will analyze the operational efficiencies, cost benefits, reliability and production data of this completion system compared to the standard completion practices being implemented today. Introduction Horizontal drilling in the Barnett Shale has become the exploitation method of choice for reservoir depletion. However, the deliverability of these horizontal wells has been a direct function of the completion and stimulation methods employed to promote production. Successful horizontal drilling in the Barnett Shale has been a direct result of horizontal technological advancements, as this particular reservoir requires fracturing to proliferate production to economic and desired levels. Without fracturing these wells in multiple stages along the horizontal, the production would be marginal at best and certainly would not justify the current activity levels in the play nor justify the added expense of drilling horizontally over longer distances. Furthermore, it has been proven that the fracturing operations that are strategically placed along the horizontal interval using mechanical diversion are the optimal method for completing these wells. For cased and cemented liner applications this issue was addressed some years back by limited entry techniques, albeit with limited success in the Barnett Shale. Later completion techniques of setting bridge plugs on coiled tubing (CT) to provide mechanical isolation inside the liner, followed by perforating and then fracturing the well have been much more successful. The cement provides the mechanical diversion in the annulus while the bridge plug provides the mechanical diversion in the liner. This process is then repeated for the number of stimulations desired for the horizontal wellbore. (Figure 1) After all the stages have been completed, CT is utilized to drill out the composite plugs, thus re-establishing access to the toe of the horizontal wellbore.1 Although effective, the inherent cost of multiple interventions with CT, perforating guns and deployment of fracturing equipment needed for each stage are extremely high, not to mention very inefficient and time consuming. This coupled with the associated mechanical risks often does not allow for the optimum number of fractures to be placed along a given horizontal interval. Production using this method can also be limiting, as cementing the wellbore closes many of the natural fractures and fissures that would otherwise contribute to overall production. Additionally, there is the issue of re-fracturing at a later date. With all the perforations open, the only feasible method for re-fracturing is to run packers and plugs on a workstring using a rig, which introduces added frictional forces, thus limiting the flow rate during the frac so the optimum design cannot be accomplished. Plus the added expense of using a rig.