Subsurface stresses can cause formation faults, slippage, and reservoir compaction, which can damage or permanently shut in a well. Traditional means of detecting these failures are limited and usually require moving a costly rig onto locations, and then interrupting production to re-enter the well. This results in late detection of issues and allows limited counteractive options. A new Real Time Monitoring Compaction (RTCM) system has been developed to actively monitor strain and temperature of wells. The system consists of three key enabling technologies: A fiber optic support device deployed at the sand face, a cost effective high-flow liner system that protects the instrumentation in openhole applications, and two optical wet connects for up to 12 channels. The fiber optic support device provides a means of holding a helically-wrapped optic fiber rigidly in place at the sand face. This new technology can be installed over traditional sand screens in gravel pack or frac pack applications, with no negative impact on the sand control functionality of the screens, or the quality of the pack. The installed fiber optic provides the equivalent of a strain gauge positioned every centimeter along the length of the producing zone. For openhole applications, a high-flow liner system was developed to protect the fiber optic support device, and the control lines. This system includes a special quick connect that simplifies the on-rig assembly and allows torque transmission in an openhole deployment. Two 6-channel optical wet connects are the final key to this system, allowing a total of 12 connected channels. This game changing technology provides an information conduit between the fiber optic at the sand face and operators at the surface. The same wet connect can also be used to connect more traditional means of measurements such as pressure-temperature gauges, or distributive temperature sensing (DTS). The information relayed through this system allows the operator to infer flow and detect subsidence or compaction of the sand face before the well is compromised, allowing time to plan and execute mitigative actions. This paper will discuss the design, testing, and potential applications of this new system. Introduction The production of hydrocarbons can often cause a decrease in porosity of the rock formation containing them. This phenomenon is known as compaction. Wells can sustain significant damage as the formation layers shift or move along formation boundaries as a result compaction. Fig. 1 illustrates this type of shift caused by compaction. The wellbore on the left of Fig. 1 illustrates the original location of the well, and the wellbore on the right illustrates the same well after compaction (Earles 2010).
In July and again in September 2019, six-fiber downhole fiber optic wet-mate connections were successfully landed on fiber enabled lower completions, "lighting up" the completion from the wellhead to the reservoir. The tools that enable this technology must simultaneously align six fibers the diameter of a human hair end-to-end in a downhole environment. These deployments are the first successful installations of fiber optic downhole wet connects in the North Sea and it represents a step change in the information that can be obtained from permanently installed sensors at the reservoir in a multi-trip completion. To date, opportunities for fiber optic sensing have been quite limited in multi-trip completion systems. This has restricted the use of many fiber optic technologies to the upper completion rather than where it can provide the most impactful data - at the reservoir. This paper will present a brief history of the development and validation of this fiber optic connector system design including specific qualification testing for these North Sea wells. The fiber optic downhole wet-mate connector is a result of more than a decade of engineering design, testing and qualification. Further refinements were made with this specific group of wells in mind, and the system was optimized, assessed and tested with support from the operator. A close working relationship between the operator and the service company enabled optimization of the tools as well as the entire completion to reduce the risk of NPT and infant mortality of the equipment. The operations resulted in a successful connection of all six fibers and a fiber optic instrumented lower completion with full well surveillance capability. Six individual fibers were connected simultaneously, enabling sensing of distributed temperature, distributed acoustics, and two pressure/temperature gauges on the exterior of the lower completion with direct contact to the reservoir. Optical losses across the connector were less than 0.5 dB for all fibers. This fiber enabled completion allows the completions and reservoir engineers to gather and interpret the distributed data that obtained by the interrogators from the interaction of the optical fiber and its surrounding environment.
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