New Tools and Procedures Increase Reliability of Openhole Sidetracking Operations

Abstract

Openhole sidetracking is most commonly applied in three drilling scenarios: 1) to drill a horizontal lateral from the main wellbore in unconventional reservoir exploration 2) to drill lateral in a multilateral well 3) to detour around a stuck fish. In most drilling operations, the risk and the economics associated with openhole sidetracking dictates that all commercially available methods and technologies be evaluated thoroughly to achieve the objective and re-establish normal drilling operations. The evaluation is more challenging in medium to hard formations or in highly deviated wells or a combination of both. Recently, the most requested application for the system has been for exploratory wells drilled in unconventional reservoir plays that are recent developments where little or no offset well data exists. In such fields there is significant risk in drilling a horizontal lateral because reservoir characteristics are not well known. The logical step therefore is to rely on the conventional methodology or on the historical experience of field engineers working the region. Traditionally, the predominant openhole sidetracking methodology started with setting a cement plug followed by a directional BHA once the cement hardens. The success of the plug setting operation depends on formation compressive strength, degree of downhole temperature/pressure, wellbore deviation, cement plug depth, quality of cement and cure time. The consequences of plug failure are extra trip time, a new cement plug, loss of drilling days and reconfiguration of drilling trajectory. A recent R&D effort has identified a new method and associated tools that can be effectively utilized to increase operational reliability in openhole sidetracking and to save costs in terms of time and materials. Single trip retrievable openhole sidetrack system:The system is designed for multilateral wells where access to the main bore is a requirement. The system is equally applicable in situations where cement plugs are ineffective such as in medium to hard formation or in highly deviated holes. No cementing operation is required.Cementing openhole system with anchor:The system is designed for unconventional reservoir exploration where the bottom hole is required to be plugged with cement once the pay zone has been identified and kick-off point for a lateral is confirmed. With the anchor firmly holding the system in place, the operator does not have to wait until the cement is fully cured. The solid ramp encased in the cement is used for sidetracking.Cementing openhole system without anchor.This system is designed for wells where there is a hard bottom available. The cement holds the system firmly at the bottom while a solid ramp encased in the cement is used for sidetracking purpose. The paper discusses mechanical and operational features of above system along with their respective field performances. The paper will also describe challenges faced in field runs, how those were overcome, the lesson learned and potential system modifications.