Maximize Recovery by Minimizing Production Delays and Shut-ins

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Technology Update The greatest challenge facing the oil and gas industry, particularly in this low-price environment, is to increase recovery rates. Experts in multiple disciplines across the industry are focusing on it because even a small improvement in recovery factors can make a major impact. To meet this challenge, the industry must do more than look to new, stepchange technologies; it must question current practices. For example, the practice of delaying first production after the multistage fracture stimulation of wells is widely seen as a sound operating strategy. Additional shut-ins, whether intentional or unexpected, are a part of everyday well operations. However, a growing body of evidence shows a negative effect on wellbore connectivity with the reservoir. A recent study examined more than 360 wells in six North American shale plays to determine the effect of production delay and shut-ins (Crafton and Noe 2013). The analyses showed that delaying production quickly damages wells, thus affecting wellbore connectivity and production. A similar result was found for shut-ins, with a strong correlation between the number of shut-ins and incurred damage. One of the mechanisms causing this damage is the energy stored in the fluid/ fluid interfaces in the form of a capillary pressure difference. Historically, the pressure difference has been understood to be relatively small, but in shale plays, it can easily be of the same magnitude as the original reservoir pressure. The study also examined the potential benefit of using a persistent interfacial tension management (pITM) nanofluid to mitigate these negative effects and found that in cases of production delay or shut-in, wells treated with pITM nanofluid showed improved connectivity and production compared with untreated wells. Therefore, the reduction of interfacial tension has the effect of reducing the amount of energy, or pressure drop, needed to allow flow to begin. The Study Methodology To determine the effect of production delay and shut-ins, two metrics were used to compare well performance. The first was the “apparent fracture length,” which describes the degree of connectivity between the wellbore and the reservoir. This value was normalized for proppant weight placed and determined based on flowback pressure and production data, using the reciprocal productivity index approach (Crafton 1997).