Identifying Bypassed and Ineffectively Stimulated Layers In A Well With Commingled Production From Multiple Layers: Mesaverde Case History
- David P. Craig (Reservoir Development Services) | Chad Eric Odegard (Williams Production)
- Document ID
- Society of Petroleum Engineers
- SPE Unconventional Reservoirs Conference, 10-12 February, Keystone, Colorado, USA
- Publication Date
- Document Type
- Conference Paper
- 2008. Society of Petroleum Engineers
- 3.2.3 Hydraulic Fracturing Design, Implementation and Optimisation, 3 Production and Well Operations, 2.4.3 Sand/Solids Control, 4.1.2 Separation and Treating, 5.1.1 Exploration, Development, Structural Geology, 5.4.2 Gas Injection Methods, 5.6.1 Open hole/cased hole log analysis, 2.5.1 Fracture design and containment, 5.6.9 Production Forecasting, 2.2.2 Perforating, 5.6.3 Pressure Transient Testing, 4.1.5 Processing Equipment, 1.6 Drilling Operations, 5.6.4 Drillstem/Well Testing, 5.8.1 Tight Gas, 4.6 Natural Gas, 5.1.5 Geologic Modeling, 4.3.4 Scale, 3.3.1 Production Logging
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In an effort to examine well and reservoir connectivity for wells drilled through multiple low-permeability stacked lenticular reservoirs, we present case histories from the Piceance basin of Western Colorado. We review the completion and subsequent abandonment of an air-drilled high-angle slant hole through the Williams Fork sandstones in Grand Valley field as well as a high-angle slant hole drilled through and completed in two Williams Fork Mesaverde sandstones. We also review a case history describing single-entry-point fracture treatments in vertical wells designed to "frac into?? sandstones near the entry point, and we describe a post-frac evaluation of propped fracture communication with sandstones adjacent to the single entry point. Lastly, we present a case history showing the results of a refracture-candidate evaluation and isolated-layer restimulation pilot program in the Piceance Basin where it is known that between 10% and 30% of the Meseverde layers targeted for fracturing are ineffectively stimulated or inadvertently bypassed during primary fracturing operations. The refracture-candidate pilot program provided the following.
- An evaluation of production logs as a refracture-candidate diagnostic.
- An evaluation of short-term pressure buildup tests as a refracture-candidate diagnostic.
- An evaluation of fracture-injection/falloff tests as a refracture-candidate diagnostic.
Four discrete Mesaverde sandstones were tested as part of the refracture-candidate pilot program. Of the four layers selected for testing, numerous microseismic events were mapped during the initial fracture treatments in two, and no events were recorded in the other two. The refracture-candidate pilot program included recording a new production log and completing short-term pressure buildup and nitrogen fracture-injection/falloff tests in each isolated layer. The nitrogen fracture-injection/falloff tests confirmed the microseismic mapping during the original completion, that is, layers without microseismic events did not have a conductive hydraulic fracture based on the nitrogen-injection/falloff analysis. Consequently, bypassed or ineffectively stimulated layers can be identified with refracture-candidate diagnostics.
Recently there has been renewed interest in evaluating horizontal wells in lenticular low permeability gas reservoirs as a means to increase wellbore productvity and improve gas recovery (Baihly et al., 2007). However, as noted by Baihly et al., "many" of the deviated wells produce only 10% to 30% more than offset vertical wells when the wells should theoretically produce "three to five times" the rates of veritcal wells. In the late 1980s, the United States Department of Energy funded the evaluation of a deviated well drilled at a high-angle through the Mesaverde group of the Williams Fork formation and drilled horizontal into the Cozzette in the Piceance basin of Western Colorado (Duda, J.R. and Kumar, H.K., 1988). Subsequently, at least two other high-angle deviated wells were drilled in the Piceance Basin. The only well deemed "economic" was the GR 1-3SH, which was drilled at a high angle into the Cozzette, but completed in, and produced from, the vertical section of the wellbore drilled through Williams Fork Mesaverde sands.
The first high-angle well drilled in the basin was the SHCT #1, which was drilled at 60° through the Williams Fork Mesaverde sands and drilled horizontally into the Cozzette (Myal and Frohne, 1991). After losing the original well and side-tracking, the Cozzette sand was completed, produced, and isolated before pumping two fracturing treatments in two paludal Mesaverde sands. No additional fracture treatments were pumped, and after producing for a few years, the SHCT #1 was shut-in in 1997.
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