Moving Toward Simpler, Highly Functional Multilateral Completions
Authors: Emerson A.B. , Westgard D.J. 
Published: July 2010

This paper discusses the development, application, and operational advantages of a TAML Level 3 multilateral completion system. It combines the simplicity of lower-level systems with the extended functionality of full re-entry into both the mainbore and lateral completions of wells that do not require pressure integrity at the junction.

To obtain re-entry and flow control in both wellbores of a multilateral application, the previous mindset was to add more completion equipment to handle the need for more functionality. The early well completions categorized as Level 3 multilaterals were constructed using a flow-through guidestock and slotted liner or screen in the lateral, which was anchored back to the mainbore by a liner hanger packer. Flow was allowed through the flow-through guidestock from the mainbore completion, where it became commingled with the lateral production via perforations or slots in the lateral liner overlap in the mainbore. The challenge was to provide a means for allowing mainbore reentry. With this increased functionality, Level 3 could be a viable, simple replacement for Level 4 ML's as well as the Level 1 and 2 completions.

With a focus on simplicity, design iterations led to the development of a system that would be mechanically basic (no moving parts) and easy to install. To date, more than 80 Level 3 Hook Hanger junctions have been completed, with most in the Orinoco Heavy Oil Belt in Venezuela. The authors will summarize several case studies, explain decision-making parameters for selecting this type of multilateral completion system, and discuss its application in Canadian oil and gas operations.

Introduction

To obtain reentry and flow control in both wellbores of a multilateral application, the mindset has been to add more completion equipment for more functionality. In an effort to make multilateral risks more acceptable, Baker Oil Tools began to develop multilateral completion systems that were simpler and less risky to install. Even though there are six multilateral categories, most multilateral applications fall into two simple groups:wells that require pressure integrity at the junction, andwells that do not require pressure integrity at the junction.

For maximum functionality in both groups, the focus is on developing Level 3 (pressure integrity not required) and Level 6 (pressure integrity required) multilateral systems that address a wide variety of multilateral well applications.

TAML Classifications

In an effort to provide parity when comparing multilateral systems industry wide, a classification system was developed by TAML (Technology Advancement for Multilaterals), a consortium group comprised of operators and service companies. The classification system divides wells into "levels" depending upon junction functionality. Figure 1 illustrates the TAML's level definitions(1). Based on these definitions, only Levels 5 and 6 provide pressure integrity at the junction. However, Level 5 requires a complex configuration of isolation packers to isolate the junction to provide pressure integrity, coupled with a high risk junction construction process. Level 6 multilateral completions, in contrast, are much simpler in design and implementation.