Oriented Perforation to Prevent Casing Collapse for Highly Inclined Wells
- Nobuo Morita (Waseda U.) | Harry McLeod (Conoco Inc.)
- Document ID
- Society of Petroleum Engineers
- SPE Drilling & Completion
- Publication Date
- September 1995
- Document Type
- Journal Paper
- 139 - 145
- 1995. Society of Petroleum Engineers
- 3.2.3 Hydraulic Fracturing Design, Implementation and Optimisation, 2.2.2 Perforating, 4.2.3 Materials and Corrosion, 2.4.5 Gravel pack design & evaluation, 1.6 Drilling Operations, 5.3.4 Integration of geomechanics in models, 1.14.1 Casing Design, 3.2.5 Produced Sand / Solids Management and Control, 1.14 Casing and Cementing, 2.4.3 Sand/Solids Control
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This paper shows that the oriented-perforation technique is an effective method to control casing collapse problems for highly inclined wells. Three wells were perforated with 180° phasing in the maximum in-situ stress direction. These three wells did not experience casing collapse, while surrounding wells with the standard perforation technique did. Two of the three wells with oriented perforations experienced significantly reduced sand problems. Numerical analysis was conducted to compare how effective oriented perforations were in minimizing casing failure when a sheared zone was created around a well during drilling and production.
The effective overburden pressure is generally the largest principal in-situ stress, and its value increases significantly with hydrocarbon production. Because stress orientation is perpendicular to the axis of highly inclined wells (including horizontal wells), borehole stability during drilling, sand production during hydrocarbon production, perforation failure, and casing failure are different from those observed in vertical wells. If a well is highly inclined, the significantly different horizontal and vertical stresses yield two sheared zones around a borehole during drilling. If the well is perforated with a standard method after casing is cemented, cavities tend to form in the sheared formation because of sand production. The stress concentration in the casing in the minimum in-situ stress direction significantly increases because of the highly directional stress and the cavity created behind the casing. Casing collapse tends to occur as a result of the high stress concentration. However, if perforations are shot in the maximum in-situ stress direction (up-down direction for inclined wells) with 180° phasing, the perforation cavities are hardly enlarged because the perforation is shot in the less-sheared orientation, reducing perforation cavity enlargement and casing collapse problems. Even if the cavities are enlarged, the evolution of cavities occurs in the direction of less casing-stress concentration, resulting in significantly reduced casing collapse problems. This paper focuses on the following ideas:
Oriented perforating eliminates casing collapse problems for highly inclined wells or wells drilled in a tectonically active area.
Oriented perforating reduces sand production problems in wells with a highly directional in-situ stress state if the formation has intermediate strength.
In addition to field experiences, a thorough numerical model analysis is conducted using field data.
|File Size||430 KB||Number of Pages||7|