Fiber-optic sensors have been widely deployed in various applications, and their use has gradually increased since the 1980s. Distributed fiber-optic sensors, which enable continuous and real-time measurements along the entire length of an optical fiber cable, have undergone significant improvements in underlying industries. In the oil and gas industry, distributed fiberoptic sensors can provide significantly valuable information throughout the life cycle of a well and can monitor pipelines transporting hydrocarbons over great distances. Here, we review the deployment of fiber-optic Rayleighbased distributed acoustic sensing (DAS), Raman-based distributed temperature sensing (DTS), and Brillouin-based distributed temperature and strain sensing (DTSS) in the oil and gas industry. In particular, we describe the operation principle and basic experimental setups of the DAS, DTS, and DTSS, highlighting their applications in the upstream, midstream, and downstream sectors of the oil and gas industry. We further developed a prototype of a fiber-optic hybrid DAS-DTS system that simultaneously measures vibration and temperature along a multimode fiber (MMF). The reported hybrid sensing system was tested in an operational oil well. This work also discusses the challenges that might hinder the growth of the distributed fiber-optic sensing market in the petroleum industry, and we further point out the future directions of related research.
An optical time-domain reflectometer (OTDR) is incapable of providing sensing or diagnostic information within dead-zones. We use a two-mode fiber (TMF) and a photonic lantern to completely overcome the main OTDR’s dead-zone originating from the front facet of optical fiber. This is achieved by injecting the optical pulses of the OTDR in the form of the fundamental mode and meanwhile collecting the Rayleigh signals associated with the higher-order modes. Using the reported TMF-based OTDR, we accurately sense the position and frequency of a vibration event located within the dead-zone as a proof-of-concept demonstration.
Summary In this paper we focus on electrical-submersible-pump (ESP) failure caused by scale buildup. Weak fluctuations recorded in the motor current signals several weeks before a failure indicate a change in the motor load. Advanced signal analysis of the motor current data reveals the presence of a dynamic characteristic in the ESP signal during rapid scale buildup in the pump stages. On the basis of the raw data from the motor current draw, a dynamic cascade can be identified in the current marked with the superimposition of several characteristic frequencies added over time that develop into a chaotic trend. Our analysis was conducted with different signal-processing tools, such as Fourier transform, wavelet transform, and chaotic attractors, which described the nature of the scale signature in the current logs. This analysis was the first step toward developing a real-time diagnostic tool for predicting ESP failures.
The present paper is concerned with a study of electrical submersible pump failure due to scale build-up. From motor current signals recorded several weeks before the failure, weak fluctuations were recorded, indicating a change in the motor load. The advanced signal analysis of the motor current data revealed the presence of a dynamical character of the electrical submersible pump signal when scale started rapidly building up in the pump stages. Based on the raw data from the motor current draw a dynamical cascade was identified from the current marked with the superimposition of several characteristic frequencies added in time and developing a chaotic trend. The analysis is conducted with different signal analysis recognition tools such as Fourier transform, wavelet transform and chaotic attractors, which describe the nature of the scale signature in the current logs clearly. This analysis can be the first step towards developing real time diagnostic tools to predict ESP failures and acting accordingly.
High sour fields beyond 10% H2S concentration are considered one of the severe environments that require suitable tubular components and accessories in upstream environment to ensure sustainable production. Such environments represent a challenging operating envelop where durability and safety are the top concerns due to higher H2S concentration at a higher partial pressure and higher temperature (HPHT). The risk is amplified for the wells with higher than 10% H2S concentration, namely the High H2S wells, and those exceeding 25% H2S concentration which are typically labeled as Ultra-High H2S wells. Corrosion in gas operations can be aggravated in downhole where high H2S at higher temperatures pose additional challenges. Selection of proper material to ensure a sustainable well condition is one of the important elements for the development of these HPHT gas wells. Various challenges were identified, including the selection of cost-effective material which is capable of withstanding short and long term H2S and CO2 partial pressures as well as control generalized CO2 corrosion, sulfide stress cracking (SSC), and stress-oriented hydrogen induced cracking (SOHIC). With the advancement of Non-Metallics (NM) materials in several applications across the O&G sector, it holds a promise to provide an alternative material solution in lieu of CRA alloy material for the HPHT downhole applications. NM materials are lightweight and they can be designed to withstand higher strength capability in addition to their outstanding corrosion resistance properties in a high H2S environment. Moreover, they can be engineered to fulfill the intended application due to their high design flexibility and durability. In the downhole applications, there is a number of NM products that have been implemented in sour environments, including sealants as well as downhole accessories and tools, where the list of NM technologies is considerably growing. This paper highlights the concept of using NM products such as coiled tubulars, pressure control equipment and elastomers as well as the challenges on the development and deployment of these key components in high sour fields.
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