Traditionally, operators have had limited options for conducting remedial work on lateral re-entries through milled-casing windows. This limitation is due to the necessity of using a "bent joint" of pipe to guide tools through the window. If a bent joint of pipe cannot be attached to the end of the assembly (e.g. a drilling assembly), a whipstock is required to deflect the assembly out the window. Setting a conventional whipstock requires the use of orienting tools that add significantly to the wellcost. This paper describes the world's first applications of unique technology that helps solve these problems by facilitating the exiting of milled-casing windows with service tool assemblies during remedial operations. The system uses the patent-pending "self-locating" lateral re-entry technology as an integral component of the Lateral Re-entry Whipstock to assure the proper orientation and elevation of the whipstock tool face with the casing exit window. The technology described in this paper has bearing on TAML Level II1 junction re-entry operations for clean out, production enhancement, increased reservoir drainage, zonal isolation, and re-completion of lateral wellbores in multilateral completions. Introduction The Permian Basin is an area where re-entry style horizontal drilling from existing wellbores has been used extensively. Drilling horizontal laterals from existing wells is more economical than drilling new wells because the costs of drilling and running casing down to the producing formation is eliminated. Due to reservoir pressure depletion, many re-entry horizontals require the use of artificial lift. In order to maximize drawdown in a pressure-depleted reservoir, the downhole pump should be set below the lateral's window. Consequently, the whipstock used to mill the casing window and drill the horizontal lateral wellbore must be pulled before installing the pump. The Challenge. Any remedial work to be conducted inside these re-entry horizontals can be a challenge because the drilling whipstock is not in the well to guide the workover string out through the casing window. Therefore, other means of guiding the string out the window must be devised. The most commonly used method locates the window with a "bent sub" on the end of a workstring. While this is often sufficient, the "bent sub" limits the assemblies that can be passed through the window. Some assemblies (e.g. drilling) are too stiff or large to be deflected over to and out a casing window even with the aid of a bent sub. The operator of the North Indian Basin Unit wanted to sidetrack an open-hole horizontal lateral in order to reach an untapped area in the reservoir. This objective meant that they were faced with the challenge of passing a 4–3/4-in. directional drilling assembly through a 7-inch casing window.
Multilateral wells in the Middle East Region usually have been completed as non-access, single-selective or limitedaccess, dual-selective wells. These methods have limited the operator's ability to monitor and enhance a well's production and can lead to total loss of production during large-scale work-over operations. Advances in multilateral (ML) completion technology have developed unique completion systems that have the capability to connect horizontal laterals to parent well-bores and allow segregated production and intervention in new or existing well bores at any time in the life of the well. Recent multilateral wells in Arabian Gulf offshore fields have enhanced productivity using innovative techniques to satisfy the completion, workover, and intervention requirements of dual producing wells. This paper will discuss case histories in which dual completions with and without pressure-isolated junctions (TAML levels 4 and 5) were developed and used. The completions were run in both new and existing wells, in both preplanned and workover scenarios. The operator's requirements were satisfied in each case. Their success has pushed the envelope for dual-lateral completion and workover in offshore fields of the Middle East. The techniques discussed are applicable to Level 4 and 5 ML wells. The successes of these installations can be attributed to the dedicated team's pre-planning of contingency methods, drilling operations, wellbore preparations, components of the completion system, and running procedures. The case history data will identify the value gained from each stage of the planning strategy. Dual multilateral completion technology includes various techniques for maintaining integrity in junction construction, completion configuration, and running techniques that combine to:Facilitate multilateral technology application when varying production conditions exist in the same wellSegregate a dual configuration for isolated or commingled production and dual segregated reentryReconfigure existing commingled production for segregated production, isolation, reentry, and rig-less interventionRestore hydraulic integrity at failing lateral junctionsEnhance effectiveness of production logging, stimulation, and rigless intervention for remedial operationsReduce initial construction cost and risk with a completion that considers the life-long production profile of the well. History In the earlier generations of ML technology, laterals were not accessible with tubing after they were drilled and served only to provide a path for drainage in additional productive sections. In the last few years, however, many innovations in the construction of multilateral wells have taken place. The next generation of multilateral improvements focused on increasing integrity of the wells and their productivity. These improvements included the development of drop liners, cemented liners and mechanically tied back liners. This generation of systems allowed the installation of many features, including packers in the main and lateral wellbores as well as flow-control features. The generation of multilaterals now available provides a full range of accessibility, flow control options, segregated through-tubing access to each lateral, pressure isolated junctions, and capabilities to enable full workover applications to be performed that can upgrade the completion at any time in the life of the well. This evolution has allowed each lateral to have all of the features of an independently drilled well, which has been the goal of multilateral well designers since the beginning. ML well designs can now be adapted to most reservoir management and production applications. This paper reviews the current generation of dual multilateral completion applications and will review their usage in the Middle East region.1,2,3,4 Junction Types The junction classifications from the Technical Committee for the Advancement of Multi Laterals (TAML) will be used to describe the complexity of the junctions of these wells. (See Figs. 1a, 1b, and 1c.) These are well described in the literature. Further, there are three main types of completions that are used in multilateral wells - non-access, selective access, and segregated access.5
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