Unconventional Shale Play: Multilateral Technology and Selective Fracturing

Abstract

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 163959, ’Unconventional-Shale-Play Selective Fracturing Using Multilateral Technology,’ by Doug G. Durst, SPE, and Mario Vento, SPE, Halliburton, prepared for the 2013 SPE Middle East Unconventional Gas Conference and Exhibition, Muscat, Oman, 28-30 January. The paper has not been peer reviewed. Drilling, completing, and fracturing of unconventional-formation wells in North America have become commonplace for producing natural gas. It is less common to drill, complete, and fracture treat multiple lateral branches from a single main wellbore. Augmenting a multilateral well with selective fracturing of each leg is as straightforward as fracturing a single-horizontal well. In this project, a plug-and-perforate system was used to address ten or more intervals in each leg, with average stimulation pressures of up to 9,000 psi. Introduction Multilateral solutions enable working within a limited surface area, generating a reduced footprint while draining a much larger volume of reservoir from a single surface location. A few multilateral wells can minimize the effect, visibility, and liability of drilling operations to drain the entire reservoir, especially in environmentally sensitive or protected areas. Potential advantages of a multilateral system can be broken into two broad categories. First, reserves can be increased or production can be increased or accelerated over the life of the well. Second, the tangible and intangible costs of the project can be reduced. Stimulating a Multilateral Well Earlier techniques in vertical wells used conventional perforating, typically followed by ball diversion for isolation. Horizontal wellbores were treated with a few widely spaced intervals (four to eight zones), then longer horizontal sections were treated (with up to 90 zones) by use of newly developed techniques and systems. Originally, ball-actuated fracturing-sleeve completions were limited to 15 to 20 intervals because ball-size increments were limited by the internal diameter (ID) of the fracturing string. New systems are available in which additional subintervals are created within the original primary intervals. With this system, five metering valves, plus one baffled valve, can be placed within the previously defined single interval. Thereby, it is possible to have six valves within each of the (up to) 15 primary intervals, for a maximum of 90 valves or 90 points to initiate fractures within a horizontal wellbore, compared with the previous limit of approximately 15 intervals.