Effect of Frequent Well Shut-In's on Well Productivity: Marcellus Shale Case Study
- Saurabh Sinha (University of Oklahoma) | Kurt J. Marfurt (University of Oklahoma) | Bhabesh Deka
- Document ID
- Society of Petroleum Engineers
- SPE Eastern Regional Meeting, 4-6 October , Lexington, Kentucky, USA
- Publication Date
- Document Type
- Conference Paper
- 2017. Society of Petroleum Engineers
- 5.8 Unconventional and Complex Reservoirs, 5.2.1 Phase Behavior and PVT Measurements, 2.4 Hydraulic Fracturing, 5.5.8 History Matching, 4.2 Pipelines, Flowlines and Risers, 5.5 Reservoir Simulation, 3 Production and Well Operations, 2 Well completion, 4.6 Natural Gas, 4.6 Natural Gas, 5.2 Fluid Characterization, 5 Reservoir Desciption & Dynamics, 5.8.2 Shale Gas
- geomechanics, Expected Ultimate Recovery (EUR),, shut-in, Net Present Value (NPV), Decline Curve Analysis (DCA)
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Well operation is one of the key foundations for optimal production of hydrocarbons from unconventional shale plays. However, optimal production practices do not follow the versatility of "one size fits all" phenomenon. Completion strategy, Pressure-Volume-Temperature (PVT) properties and petrophysical properties vary from play to play. Hence, the well operating practices should be custom tailored to suit the completion and fluid properties.
In this paper, we propose optimal shut-in practices for dry gas shale reservoirs. We elaborated our study from a Marcellus shale dataset. Marcellus shale dry gas window has in place fluid properties that differ from liquid rich reservoirs like Eagle Ford and Wolfcamp shales. Therefore, production best practices borrowed "as-is" from liquid rich reservoirs and applied to dry gas reservoirs (or vice versa) may not affect the well ultimate recoveries in a positive manner and in some cases, may even reduce the expected ultimate recoveries (EUR's).
We show that the practice of "well conditioning", "resting" or "soak-in" i.e. shutting in the well for a significant time after hydraulic fracturing and before connecting to pipeline as well as frequent shut-in impedes the water unloading from the dry gas reservoirs. This leads to reduction in matrix permeability with an additional skin introduced by water imbibition.
Our methodology by simultaneously history matching gas rate, flowing bottomhole pressure (FBHP) and water rates in a reservoir simulator. We observe that after shut-in, water to gas ratio (WGR) decreases and gas rate increases. However, this increased gas rate is accompanied with higher declines in rates and pressures and ultimately leads to lower EUR's. The reduction in EUR in our case is modeled as a function of water saturation increase in the matrix due to imbibition. Thus, EUR in our study is a function of duration of shut-in and the time in well life at which the shut-in occurs.
|File Size||1 MB||Number of Pages||10|