A permanent downhole gauge (PDG) in an intelligent completion provides real-time data concerning downhole conditions that can be used to assess the well environment and make informed decisions regarding reservoir and well integrity management. These gauges are permanently installed in severe downhole environments and rarely retrieved to surface for analysis or maintenance. Despite harsh conditions, the gauge is designed to achieve high operational reliability at temperatures of up to 200°C and pressures that reach 30,000 psi. The scope of this paper includes successful application of design for reliability (DfR) principles to streamline the product development process for high-pressure/high-temperature (HP/HT) environments. Equipment and material reliability is critical to success in HP/HT environments. This paper discusses a reliability focused product development approach and highlights the application of DfR techniques used to qualify a downhole gauge for an operator's prelude floating liquefied natural gas (FLNG) project offshore northwestern Australia. In this major well development project, downhole gauges are used for real-time permanent monitoring at high temperature downhole conditions. High operational reliability of a downhole gauge is important to ensure functionality throughout facility commissioning, startup, and operations after a well suspension period. Reliable recording of well integrity data during the well suspension period also helps improve operational simplicity. The DfR process is a systematic, streamlined, and concurrent engineering program designed to meet system reliability targets. This paper examines establishing a reliability specification for a downhole gauge, managing design risk using design failure mode and effect analysis (FMEA) followed by design robustness testing using highly accelerated life tests, leading to a reliability demonstration test program to achieve target system reliability. This paper highlights an application of optimized DfR strategy along with an efficient reliability qualification test that resulted in successful product development. Improvements to the quality process to ensure reliability consistency between testing and the final commercial deployed gauges are also addressed in this paper. Additionally, this paper highlights strategic application of a powerful DfR process that aided design de-risking and helped attain system reliability targets, thereby, helping the operator meet its needs. Also demonstrated is how an efficient DfR process led to streamlined product development of a permanently installed downhole gauge resulting in cost and time-to-market improvements while establishing reliability.

The acquisition of accurate downhole pressure measurements from land-based unconventional wells can enable analysis of pressure data that can be used to help optimize and reduce the cost of fracture treatments and improve overall well productivity. The pressure data for the analysis are obtained from downhole electronic gauges in both the target well and in the surrounding observation/monitoring wells. The objective of this paper is to demonstrate the value monitoring this downhole pressure data can provide throughout the life of land-based unconventional wells. The paper also describes the selection of the equipment, the steps necessary for its successful installation, project commissioning, and acquisition of reliable data throughout the life of the well.Historically, operators have experienced less-than-desirable success rates for long-term downhole pressure monitoring, especially in multizone, openhole, horizontal wells. This paper discusses how the success rate of these installations has been significantly improved by the implementation of a program with a well-defined series of steps that includes detailed planning (completing the well on paper exercise), onsite function testing of equipment prior to installation, and stringent attention to job execution detail. This program is based on the fact that adoption of the proper selection criteria for the application is critical to selection of the proper type of monitoring equipment and to the operational and economic success of these pressure-monitoring projects.

Intelligent completion technology helps operators optimize life-of-well production, without costly intervention. Reliable and fit-for-purpose intelligent well systems help operators collect, transmit, and analyze downhole data, remotely control selected reservoir zones, and maximize reservoir efficiency during production. Permanently installed downhole electronics, instrumentation, and sensors are key features of any intelligent well system. Because these systems operate in severe downhole environments and are rarely retrieved to surface for analysis or maintenance, reliability testing beyond standard qualification testing is essential to achieve high operational reliability in high-pressure/high-temperature (HP/HT) scenarios. This paper presents the primary differences, benefits, and drawbacks of reliability test design techniques and describes an optimized approach to designing an integrated reliability test. It also highlights the importance of deriving a comprehensive reliability statement to meet performance guidelines during HP/HT operations. Reliability tests can be broadly classified into test-to-failure and test-to-success categories. During test to failure, test specimens are run until failure occurs. Failure of a significant proportion of test specimens generates time-to-failure data, which are used to estimate system reliability. Whereas, test to success is set up as a success test; therefore, no failures are expected during testing. All test specimens should survive the designated amount of test time to demonstrate the minimum system reliability. The data obtained at the end of a reliability test are used to develop a product reliability statement. For HP/HT applications, a reliability statement should be measureable and associated with a failure definition. It should also incorporate a usage profile and specify the lifetime. The key elements of a comprehensive reliability statement are probability of success, associated confidence, operating conditions, and lifetime. Reliability tests are primarily used to detect underlying design-based wear out failure mechanisms and latent production defects. A reliability test beyond standard qualification helps achieve overall system reliability by providing opportunities to help improve the design and production processes. These tests should be designed as a set of well-defined accelerated tests to help save product development time and meet the system reliability target for HP/HT applications. The conclusion of a reliability test leads to a comprehensive and meaningful product reliability definition. This paper discusses the methodology and guidelines used to design an efficient reliability test for HP/HT applications. It also highlights the key input parameter control strategies for robust reliability testing. This paper presents the reliability test results integrated with a comprehensive reliability definition. A case history of an intelligent well system is presented to demonstrate the differences between the test-to-failure and test-to-success approaches, along with their advantages and disadvantages. The examples demonstrate how an efficient reliability test integrated with a comprehensive reliability definition can help lead to cost and time-to-market improvement for HP/HT well completion advancements.