Barnett Shale Drilling and Geological Complexities—Advanced Technologies Provide the Solution

Abstract

The Barnett Shale field of North Texas is the most prolific and fastest growing natural gas field in North America.1 The field has a multi-trillion cubic feet equivalent upside potential, but efficient extraction of natural gas from the Barnett shale poses drilling and geological challenges. Geological complexity of this field requires precise placement and drilling of the well as per the directional well plan. Some of the major drilling challenges that affected drilling efficiency were downhole drill-string dynamics, high torque and drag, hole pack-offs and loss circulation. Engineers determined that early detection of downhole problems such as high vibrations, poor hole cleaning and high equivalent circulating densities (ECD) were key to improving drilling performance. To overcome these challenges state-of-the-art advanced technology tools were run to acquire real-time drilling data and images. Real-time drilling data acquired was inclination/azimuth close to the bit, bore/annular pressure and vibration/stickslip. Drilling data gathered in real-time were crucial to detect and eliminate potential drilling problems before they became a problem. Real-time geological data transmitted to surface were formation resistivity and azimuthal gamma ray measurements. High-resolution images were developed from real-time azimuthal gamma ray measurements. These images could be utilized to precisely detect bed boundaries and accurately estimate formation dips. This strategy has been implemented to drill several wells in the Barnett Shale with excellent results. Advanced technologies have helped in significantly improving drilling performance and in precise placement of the wellbore. Significant reduction in rotating hours has been achieved. Introduction The Fort Worth Basin covers approximately 15,000 square miles and is located in north-central Texas.2,3. This basin is a shallow, north-south elongated trough and is bounded on the north, northeast, and east by faulted basement uplifts of the Red River Arch, the Muenster Arch, and the Ouachita Structural Front. The southern limit is defined by the Llano Uplift and the basin shallows onto the positive feature of the Bend Arch to the west.2,3 In its deepest area adjacent to the Muenster Arch, the Fort Basin contains a maximum of 12,000 ft of sedimentary section.1 In this area, the Barnett Shale can reach a thickness greater than 1,000 ft.2,3 In the core area of the Newark East Barnett Shale Field, the Barnett shale is encased by tight carbonates, which act as fracture barriers during the completion process.2,3 A typical stratigraphic column2,3 of the Fort Worth basin was previously published. (Janwadkar, S. et al.: "Advanced LWD and Directional Drilling Technologies Overcome Drilling and Completion Challenges in Lateral Wells of Barnett Shale," paper SPE 110837).

Delivering Performance in Shale Gas Plays: Innovative Technology Solutions

“…This is mainly composed of soft shales in the upper section with a CCS ranging from 5,000 psi to 10,000 psi, and sandstones and limestone stringers with CCS ranging in the mid twenties to mid thirties 6 Some of the major challenges through the vertical section have been high torque and drag, hole pack-off, and loss of circulation. Drilling performance has been improved by an early detection of downhole problems, that include vibration and poor hole cleaning, long before they became a problem 10 .…”