Abstract

From deepwater exploration to onshore producing wells, solid expandable tubular technology can provide substantial savings in total well cost. Operators considering new options in well design have discovered the potential and practicality of these expandable systems. Land wells are being planned using the technology to slim wellbore design. Offshore wells have coupled the slimming well-design concept with a surface stack to enhance the drilling process.

Limitations associated with using a surface stack frequently result in well depth targets being missed. Solid expandable tubular technology provides casing design alternatives that allow access to these previously out-of-reach targets. Simply put, employing expandable technology in the surface stack process allows wells to be drilled deeper at less cost.

Early deepwater surface stack technology was limited to a four-casing string well design (13–3/8 in., 11–3/4 in., 9–5/8 in., and 7 in.). Shallower reservoirs proved to be within reach of this four-string well design, prompting identification of prospects in deeper reservoirs. These subsequent reservoirs pushed the targets to depths unreachable using the conventional four-string well design. Solid expandable tubular systems provided the technology to reach the targets by incorporating two additional casing strings (9–5/8 × 11–3/4 in. and 7–5/8 in. × 9–3/8 in.) while still maintaining hole size. Deepwater surface stack technology is evolving to a five-casing string conventional well design capability (16 in., 13–3/8 in., 11–3/4 in., 9–5/8 in. and 7 in.) with the option of incorporating three solid expandable tubular strings (13–3/8 × 16 in., 9–5/8 × 11–3/4 in., and 7–5/8 × 9–3/8 in.). Drilling wells using solid expandable tubulars with a surface stack translates into savings in wellheads and risers, mud, cement, and cuttings removal.

Solid expandable tubulars are proving to be just as adaptable and cost efficient in land well construction. Onshore wells with four-string casing designs are being slimmed so that an entire 7,000 ft well can be drilled with no hole section larger than 12–1/4 in., eliminating traditional 22 or 17–1/2 in. hole sizes. The smaller hole also increases the rate of penetration (ROP)

This paper will discuss the unique challenges of casing systems associated with both deepwater and onshore exploration. The process of identifying, planning, and executing the integration of solid expandable tubulars with surface stack drilling will be analyzed and evaluated. Diverse case histories will illustrate how these technologies can overcome the limitations of conventional technology, and do so in a cost-effective way.

Introduction

The desire to change well design and construction proved to be a primary driver behind the development of solid expandable tubulars. This goal initially required addressing the following challenges:

  • drilling in high pressure zones

  • drilling in deepwater environments

  • drilling in troublesome sub-salt plays

  • repairing and mechanically enhancing casing strings already in place

  • enhancing existing wells

As an enabling technology, solid expandable tubulars allow operators to access reserves that cannot be reached economically with conventional technology1. Expandable technology helps facilitate far-reaching, untapped applications to solve present and future drilling and development problems that cannot be resolved with conventional measures. The evolution of this technology is due in part to the documented success of using expandable tubulars to save wells in danger of not reaching their planned objective.

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