Multi-lateral drilling and completion techniques involving cased primary and lateral well-bores have become increasingly prevalent in the oil and gas industry over the past five years. The experience gained in this time has permitted technological advances which now allow operators the flexibility to plan for increasingly complex multi-lateral applications.

An effective planning process is essential to the successful drilling and completion of every multi-lateral project, whether it be a single open hole lateral application with no re-entry or isolation requirements or a complex combination of multiple laterals in different formations requiring fully selective reentry and isolation capabilities.

This paper discusses the many technical issues which must be considered when planning the drilling and completion of multi-lateral wells.

Consideration is given to the selection of the optimum drilling and completion systems for particular applications, and includes a comparison of the advantages and disadvantages of pre-milled casing window systems with those of downhole window milling techniques.

Various drilling and completion issues are then discussed in detail as they relate to the planning of multi-lateral wells. These issues include well profile considerations; cementing options; re-entry and isolation requirements; well control considerations; constraints imposed by the technology and the importance of contingency planning. A case history which serves to illustrate the importance of a comprehensive planning process is presented.

The paper presents a set of guidelines which are based on a continually increasing level of experience gained during the installation of over 100 casing window systems in various applications worldwide in addition to the extensive bench testing which has been carried out on these systems. This experience has resulted in enhanced planning processes which lead to reduced risk when implementing multi-lateral systems.

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