The Gulf of Mexico hydrocarbon potential has confounded "naysayers," who once called it the Dead Sea. The planned development of the ultra deepwater lower-tertiary play is the latest chapter in the Gulf of Mexico's ongoing viability as a major hydrocarbon basin. To economically develop this challenging lower-tertiary play requires new completion technology to handle the long, stacked pay intervals. This has generated renewed interest in multi-zone completion technology. This technology is viewed as a method that hs the potential to increase completion efficiency as well as reduce overall completion cost. These systems were once considered too complex and risky for deepwater operations; but the hope that the technology could provide increased completion efficiency and alleviate some of the issues inherent with stacked completions in deepwater has again renewed interest in pursuing this technology. Thus, the latest generation of robust, cased-hole single-trip multiple-zone frac-pack completion systems has been developed. The renewed interest for development of these systems has also been the driving force for development of an openhole multiple-zone frac-pack completion system that could ultimately provide reductions in well construction cost. This paper will provide the reader with a brief development history of cased-hole, single-trip multiple-zone completion systems and then the focus will shift to the latest generation of tool systems. The discussion will also include the reasons why the previous systems have not proliferated globally as an accepted mainstream sand-face completion technique. The sand face is one part of the completion equation. The methodology of integrating the uphole completions to the multizone sand-face completion will be briefly discussed.The improved functionality of the newest multizone systems will be described and compared to the previous-generation systems. The presentation will cover the integration testing to qualify the newest multiple-zone system and will cover trial well installations. Deepwater case histories will be presented, if available by presentation time. Single-Trip Multiple-Zone Development ChronologyThere are many ways the single-trip multiple-zone sand-control tool systems can be categorized. For the purpose of this paper and to properly define the attributes of the evolving tool systems, they have been divided into four generations. Another method of categorizing would be by dual concentric string or single concentric string, but this method fails to properly document the development and lessons learned from the earlier tool systems.

In the 1980s, economic conditions in the oilfield were demanding improvements in economic and completion efficiency, and all phases of the industry were requiring that strategies to improve cost be revisited. Sand-control completion methodologies were no exception; they were no longer capable of meeting the economic and completion-efficiency required to complete the long stacked intervals being attempted. To address this problem, a single-trip multiple-zone gravel-pack system was developed. The concept was successful for the targeted formations, but as with all new technologies, certain shortcomings concerning rathole intervals, complexity of the systems, and longer, more deviated wellbores prevented its use in all types of reservoir scenarios.An improved version that was introduced in the early 1990's attempted to address these shortcomings. This system was successfully deployed and is still being run in the Far East today. However, limitations that were still experienced with the single-trip multiple-zone systems have prevented their wide spread adoption, causing them to remain a niche completion technique predominately used in the Far East and Italy.Industrial drivers for deepwater development have again caused operating companies to revisit the viability of multiplezone systems. Once considered too complex and risky for offshore operations; the development of the ultra deepwater lowertertiary play in the Gulf-of-Mexico has provided the impetus for renewed interest in multi-zone concepts. This interest has been driving the development of the latest generation of the cased-hole multiple-zone system as well as an openhole multiplezone frac-pack-compatible completion system. The intent of this paper is to chronicle the development of cased-hole single-trip multiple-zone completion systems with a focus on the latest generation of these systemsthe systems developed for deepwater applications. The paper will also discuss why previous systems have not proliferated globally to become an accepted mainstream sand-face completion technique.The improved functionality of the newest system will be described and compared to the previous generation of systems. The integration testing to qualify the new multiple zone system is included in the discussions. Several installations have been planned, and the case histories will be included if available by paper time.

Proposal Since horizontal openhole sections are now being drilled to lengths that exceed 20,000 ft, placement of the completion string (CS) to planned total depth (TD) may not be possible under a proposed drilling plan.During the early years of horizontal-well construction, the hanging weight of the completion string was usually adequate to push it to TD. With the extreme lengths being attempted today, it is important to model the well before attempts are made to run the planned completion to determine 1) whether the strength of the CS can stand the strains (tension, compression, and torque) of installation, and 2) whether there is enough weight in the upper CS to push the lower CS to TD. A software model that uses a wide range of well parameters to enable the operator to predict possible tension loading, compression loading, and torque limits on the CS during installation has long been available. This paper discusses the software and how it can be used in modeling well completion systems. To calculate the applied forces on the completion string requires the use of a wide range of well parameters and a specialized software program that will allow the prediction of loads and stresses that can be safely applied on the CS during installation.If the modeling process indicates that the CS will not stand the stresses of installation without (1) failing from tensile loading, (2) buckling from the compression load, or (3) failing from rotational torque, a different well plan can be devised or other remedies employed. Charts developed from actual case histories illustrate how the use of torque and drag modeling can be advantageous in all phases of well completion. Introduction Frictional drag can prevent installation of a completion string (CS) to total depth (TD) of a well. This situation can be especially critical in an openhole horizontal well, since there are additional challenges inherent to gravel pack assemblies. When considering offshore development, the cost of drilling can approach, and occasionally, can even exceed $70 million.Because of the increased costs and risks in these well scenarios, the capability to accurately assess the various stresses to which the CS can be subjected during installation will be critical to well success. The technique presented in the paper provides the completion designer an additional tool in designing a completion string that can withstand the downhole stresses encountered during the running of the completion string.For example, if the modeling process indicates that the CS will not withstand the stresses of installation without 1) failing from tensile loading, 2) buckling from the compression load, or 3) failing from rotational torque, a different well plan must be devised. The operator must then formulate a new configuration, which can then be assessed using the torque and drag model for primary assessing of the capabilities of the new configuration. When considering the number of unplanned drilling issues that can prove to be detrimental to the successful completion of a horizontal openhole completion, a primary key to successful planning, drilling, and completing a well is the initial development of an organized program that foresees all possible problem areas and includes all drilling as well as completion parameters.This program should also determine appropriate bottomhole assemblies and individual tools and components.

Development of the Wilcox stacked oil sands in the Lower Tertiary fields in the Gulf of Mexico (GOM) requires zonal stimulation; however, when the decision was made to produce this formation, the stacked sand-control systems currently available would have been cost prohibitive. Thus, a special team was commissioned to develop a single-trip multizone completion system to address the challenges of producing this ultradeepwater GOM field. This paper chronicles the development, qualification, and installation of a new one-trip high-rate fracture system that meets the needs of cased-hole installations in the Lower Tertiary formations with well depths reaching 28,000 ft TVD, as well as in cased-hole shallow-depth wells in the Asia Pacific area.A dedicated development team began tool-system development in January 2007. The first systems integration test (SIT) was conducted in December 2007 after only 11 months. The successful SIT led to the assignment of three land wells by a major international oil company to prove out the multizone system. After two successful installations, the third installation was eliminated, because the multizone system was classified as operationally ready.Drilling issues lead to the plugging and abandonment of the planned inaugural ultradeepwater installation. The operational moratorium in the GOM in 2010 also changed the original target wells. The first commercial cased-hole installation was run in the Asia Pacific area in a shallow-depth well environment using water-pack treatments. Subsequently, multiple ultradeepwater installations have been performed to date.Lessons learned from the SIT process and from the initial installations that included the ultradeepwater Lower Tertiary fields are presented.

Currently, ultradeepwater single-trip multizone completions are commonly run (Techentien et al 2016). Looking forward, improvement and progress can be achieved by using run history, lessons learned, and best practices. In the Lower Tertiary of the Gulf of Mexico, multizone completions in which differential pressure ratings of 15,000 psi are necessary, all operational stages should be considered, including stimulation treatments and production depletion. To date, little information is published about specific downhole component design methods or standard qualification processes required by operators and/or service companies. The objective of this paper is to help educate the industry by presenting the approach of one service company to address the 15,000 psi Lower Tertiary challenge. This paper discusses the innovative qualification processes of all subsystems, including the intelligent upper completion, interfacing intermediate completion, and the sandface lower completion. The proven success of the industry-standard 10,000-psi generation IV (Clarkson et al. 2008) multizone frac-pack system (Grigsby et al. 2016) provides an installation and operating standard that is used as a basis for a 15,000-psi pressure-rated multizone system. Operators were interviewed, internal discussions with all stakeholders were conducted, and thorough reviews of current and future regulatory standards were completed to develop this methodology. This paper presents the results of these discussions and reviews the downhole components using a detailed qualification process. It also discusses the test procedures for full system validation to satisfy operator and regulatory requirements. The result is a reliable 15,000-psi differential, single-trip multizone system that incorporates an intelligent completion string for interventionless zonal isolation, control, and monitoring over the life of the well.