Abstract

Multilateral oil and gas well concepts have been in existence since the early 1900's, but advances in directional and horizontal drilling have recently made this reservoir development approach more feasible. Although numerous multilateral wells have been drilled, particularly in the Austin Chalk, until now completion methods have been limited in providing features to manage borehole stability, flow control, and well maintenance.

This paper will discuss several examples of the advances in drilling technology that have made these multilateral well development strategies possible. Information will also be provided on several simple multilateral well completion techniques as well as a multilateral system that will 1) mechanically connect the lateral liner to the parent casing, 2) allow through tubing re-entry access to selected laterals, and 3) seal the junction between the lateral and parent bore so that flow control capability can be maintained. In the latest system developed, the hole size of the lateral has been maximized in comparison to the parent wellbore casing, and full bore access to the lateral liner drift ID without restriction has been provided. Information will be presented concerning the project methods undertaken to develop this system, the bench tests that were performed for the components of the system and results of the full scale system test conducted. An "integrated development" approach with a multidisciplinarydesign team and direct producing company involvement was used in the development of the full featured multilateral completion system and proved to be an instrumental factor in the achievement of its success. In addition to information concerning application of multi-lateral completion techniques to new completions, the concept, as it has recently been applied toa recompletion, will also be discussed.

Case histories of the completion experiences of two wells in which the system has been successfully implemented as well as several earlier successful completions using other systems will be presented. In addition, details will be provided concerning the case history in which the technology was employed in a mature field. Experiences to date have shown that multilateral technology can provide technical and economic feasibility for both new installations and recompletions.

Introduction

Many enhancements have recently been made to multilateral completion systems, not only as a result of advances in technology but also because of changes in developmental concepts that have been instrumental in achieving many of the system successes. A primary factor in the increased interest in multilateral completion technology has been its enhancing impact on the economics of field development.

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