Optimization of Completions in Unconventional Reservoirs for Improved Efficiency and Ultimate Recovery
- Daniel Snyder (Packers Plus) | Rocky Allen Seale (Packers Plus)
- Document ID
- Society of Petroleum Engineers
- SPE/ICoTA Coiled Tubing & Well Intervention Conference and Exhibition, 5-6 April, The Woodlands, Texas, USA
- Publication Date
- Document Type
- Conference Paper
- 2011. Society of Petroleum Engineers
- 4.1.5 Processing Equipment, 5.8.6 Naturally Fractured Reservoir, 5.8.1 Tight Gas, 3 Production and Well Operations, 3.2.3 Hydraulic Fracturing Design, Implementation and Optimisation, 4.1.2 Separation and Treating, 2.5.4 Multistage Fracturing, 5.8.4 Shale Oil, 2.4.3 Sand/Solids Control, 4.6 Natural Gas, 2.5.2 Fracturing Materials (Fluids, Proppant), 1.10.1 Drill string components and drilling tools (tubulars, jars, subs, stabilisers, reamers, etc), 1.6.6 Directional Drilling, 1.2.3 Rock properties, 2.2.2 Perforating, 1.6 Drilling Operations, 2 Well Completion, 5.8.2 Shale Gas, 1.14 Casing and Cementing, 1.10 Drilling Equipment, 1.8 Formation Damage
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Over the last decade, an industry wide shift to unconventional plays has occurred due to advances in technology allowing for the recovery of previously uneconomic reserves. The primary objective of completions in these unconventional reservoirs is to increase the effective surface area of the well to maximize reservoir contact. Horizontal drilling and multi-stage fracturing are two technologies which have accomplished this.
The two main methods of horizontal, multi-stage completions currently used in unconventional reservoirs are cemented liner "plug and perf?? and open hole, multi-stage fracturing systems. This paper provides an introduction to unconventional reservoirs, describes the main methods of horizontal, multi-stage completions, and discusses how the choice of method can affect good fracturing practices as well as long-term production. Case study examples are presented from a variety of unconventional reservoirs including shale, tight sandstone and tight carbonate formations.
Operators working in a number of unconventional reservoirs, such as shales and other tight rock formations are experiencing faster than expected production decline rates, resulting in reduced long-term, ultimate recovery. This may be in part due to the abandonment of good fracturing practices with the advent of horizontal, multi-stage fracturing. Issues such as near wellbore conductivity, flowback, and fracture tortuosity, which can have a significant effect on the long-term production of wells, need to be considered when choosing a completion method, particularly for unconventional reservoirs.
Unconventional plays are becoming a significant part of the oil industry today and will become a bigger part in the future. It is important that the reservoirs are completed optimally to achieve maximum recovery. The information provided in this paper is applicable to unconventional resource plays worldwide.
Unconventional reservoirs. Over the last decade, an industry wide shift to unconventional plays has occurred due to the depletion of mature, conventional reservoirs, increased demand and advances in technology allowing for the recovery of previously uneconomic reserves in these plays. Unconventional reservoirs have been defined as formations that cannot be produced at economic flow rates or that do not produce economic volumes of oil and gas without stimulation treatments or special recovery processes and technologies (Figure 1) (Miskimins, 2008). Types of unconventional reservoirs include those with poor fluid-flow characteristics due to small inter-pore connections and/or stacked pay units ("sweet spots??) (Cramer, 2008).
The primary objective of completions in these unconventional reservoirs is to increase the effective surface area of the well to maximize reservoir contact. Horizontal drilling and multi-stage fracturing are two technologies which have accomplished this. The two main methods of horizontal, multi-stage completions currently used in unconventional reservoirs are cemented liner "plug and perf?? and open hole, multi-stage fracturing systems.
Although both methods have the same goal of increasing access to the reservoir through the induction of fractures along the entire length of the horizontal wellbore, they differ significantly from an operational perspective (Lohoefer et al., 2006, Seale et al., 2006, Seale, 2007).
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