Activity in the Barnett shale of north Texas has continued to surge over the past several years, and with this surge in activity has come a steady evolution of completion strategies. Most operators agree that the best Barnett shale wells are those that have the most extensive fracture network development. One of the biggest challenges facing operators has been determining which completion strategy will create the largest fracture network along with identifying the most cost-effective diagnostic methods for evaluating those strategies and ultimately optimizing the completions. This paper will describe an integrated completion diagnostic methodology for assessing and potentially optimizing Barnett shale completion strategies. The methodology described employs radioactive tracing and logging together with chemical tracing and conventional completion metrics to evaluate the effectiveness of Barnett completions. This methodology will be utilized to assess the effectiveness of four pairs of simultaneously-fractured parallel horizontal laterals located in three different areas stretching from the western edge of the Barnett "Core Area" to the western edge of the play's expansion acreage. Key completion parameters were identified that can be used to optimize future Barnett completions in this and potentially other areas within the basin. Introduction The Barnett shale is a successful development target as an unconventional reservoir in north Texas' Fort Worth Basin. The majority of the production from the Barnett is located in the Railroad Commission Newark, East field. Total gas production from all north Texas Barnett fields is in excess of 2.5 bcf/d from approximately 6800 wells, with cumulative production of 2.9 tcf as of April 2007. The Barnett is a Mississippian-aged marine deposit. Within the basin, the Barnett ranges in thickness between far less than a hundred feet in the far south and west (as it is affected by the Bend Arch and Llano highs), to over a thousand feet of thickness next to the northeastern edge (near the Munster Arch). The Barnett is typically seen as a black organic-rich shale. It is unique in its relatively low clay content and high quartz content. This mineralogical anomaly is thought to contribute to the good fracture conductivity that can be created during the hydraulic fracturing completion of Barnett shale wells. Unconformably underlying the Barnett shale is either the Ordovician-aged Ellenberger (limestone and dolomite) or a thin Simpson and Viola section. The distinction in the underlying formation is controlled by the position of the erosional limit of the Ellenberger limestone and dolomite or Simpson and Viola sections. While both instances represent a long period of sub-aerial exposure, the cave creation and subsequent karst topography development of the Ellenberger surface is of present importance and significance as it relates to the development of the Barnett shale reservoir. While most of the basin was relatively quiet through Barnett deposition, local karsts represent relatively active features that did see significant structural "development" during Barnett deposition. It is thought that this karst topography developed slowly as overburden weight collapsed the cave systems. This collapse was accommodated by the filling of Barnett lows, resulting in "ring-faulted" collapse structures with locally thickened Barnett sections. Areas of the basin that have preserved sections of the Simpson and Viola were largely "protected" from the Ellenberger's karsting effects. These areas are found in the far north and east portions of the basin, toward the Muenster Arch and Ouachita Thrust front. The Viola, where present, provides the additional mechanical benefit of providing a frac barrier during hydraulic fracture stimulation of the overlying Barnett rock.
The Granite Wash continues to be a prolific hydrocarbon producer, with over 1600 wells drilled during the last 10 years. During 2012 and 2013 an extensive development program was initiated by one operator in which 144 wells were drilled and completed with multi-stage hydraulically stimulated horizontal wells. Many of these wells utilized various types of completion diagnostics to: (1) evaluate vertical and horizontal communication within the Granite Wash, (2) identify potential horizontal loading problems and (3) diagnose long-term fracture fluid movement. This paper reviews more than two years of water-based frac fluid tracer data. It details how the individual tracers were used to quantify communication between various layers of the Granite Wash and between nearby completed offset wells. Also, toe stage frac fluid recoveries were compared to identify wells that appeared to be constrained. Data will be presented documenting specific cases of inter-well and inter-zonal communication. This will include both offset wells that had been on production prior to the fracturing treatment and offset wells that had been recently drilled.Extended sampling of individual fluid tracers can be an extremely useful tool in explaining production anomalies as they occur. On this project, the operator was able to identify the source of production changes and determine the best well intervention technique to economically increase production.
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