SPE Journal
Volume 15,
Number 3,
September 2010,
pp. 878-892
Summary
Drilling and production optimization are two closely related operations for
successful well construction and reservoir management, in particular for
multilaterals. Unfortunately, to date, analytical study for the stability of
multilaterals has been very limited because of the complex geometry and stress
state involved. This work entails a recently derived analytical solution to
estimate the safe mudweight window for wellbore stability during drilling and
to predict the maximum pressure depletion for a stable junction during
production. The presented solution is capable of handling the complexity of the
3D anisotropic state of stress as well as any main-bore and lateral size,
inclination, and azimuth. The study shows that the design of multilateral
junctions, especially inclination and azimuth of both wellbores with respect to
regional in-situ stresses, plays a crucial role in the multilateral-junction
stability and the critical pressure depletion to prevent solids production and
wellbore collapse. A field case study of an openhole multilateral well drilled
in the Khuff-C formation, Ghawar field, Saudi Arabia, is analyzed here with
drilling data, core-retrieved rock properties, and pressure-depletion and
production estimates. The results showed alternative optimized completions that
could have been applied early in the drilling and branching of the laterals.
Practical guidelines concerning branching optimization have been established
for junction planning and execution. The new analytical modeling has also been
calibrated with a published peer-reviewed large-scale experimental program
simulating both the anisotropy of far-field stresses and the complex junction
geometry with exceptional qualitative and quantitative results.
© 2010. Society of Petroleum Engineers
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History
- Original manuscript received:
11 September 2009
- Meeting paper published:
22 September 2008
- Revised manuscript received:
15 October 2009
- Manuscript approved:
17 October 2009
- Published online:
1 April 2010
- Version of record:
22 September 2010