Distributed sensors for oil logging using power cables and sensing optical cables for temperature measurement-INNO

分散型光ファイバーセンサー 温度などのさまざまなパラメータを測定できます, ストレス, ガス濃度, 油井内の混相流と, しかし実際には, 最も成熟したテクノロジーは温度センサーと応力センサーです. 特に温度センサー, 技術的に成熟しているだけでなく、広く使用されています. 油井検出中, 粘度や圧力などの他のパラメータは、温度データに基づいて間接的に導き出すことができます。.

1. 電力ケーブルの分散温度測定用センシング光ケーブル

都市部の電力ケーブルの敷設方法は、土壌に直接埋設するか、トンネル内のケーブルトレイ上に設置するのが一般的です。, 後者が最も一般的な方法です. センシング用光ケーブルはケーブル回路の1相の表面に固定されています, これは一般に温度上昇がより高い相です, インターバルバインディングによる.

の temperature measurement system host measures the surface temperature of the cable through the Raman scattering effect of optical fibers, and can calculate the real-time temperature of the cable conductor through the cable’s thermal conductivity equation. The current technological level can achieve a temperature measurement accuracy of 1 ℃ and a position resolution of 1 meter within the cable length. Through this distributed temperature measurement system and analysis software, the fire, critical insulation breakdown, current conveying load, real-time current carrying capacity, and other states of the cable can be observed. It should be noted that the temperature on the surface of the cable is sensed through the 光学的 fibers in the cable, while the surface in contact with the cable is the surface of the optical cable. したがって, in practical applications, the temperature sensing system ignores the structure of the sensing optical cable, and the deviation of the test data is within a completely acceptable range.

The optical cable used for temperature sensing of power cables takes into account the simple, 軽量, 難燃剤, フレキシブル, and easy to move characteristics of the optical cable structure. The sensing optical cable structure used in temperature monitoring systems for highways, 橋, and tunnels is basically the same as that used for power cable monitoring,

2. Distributed Fiber Optic Sensing Fiber Optic Cable for Oil Logging

現在のところ, the depth of oil wells being mined is generally between 3000 に 10000 メートル. 以前, electric sensors were used to detect reservoir information, installed in continuously connected steel pipes, and buried in the oil wells. This method is not only extremely inconvenient for construction, but also due to the detection signal being an electrical signal, the amount of information collected is small and the accuracy is not high due to factors such as detection distance and distortion. Later, point type fiber optic sensors represented by FBG were developed, which were connected to FBG through optical cables at locations where detection was needed. This method took a big step forward in technology, but there was still a problem of incomplete detection of oil well data information, until the emergence of distributed sensors and their application in the field of oil logging. It is insensitive to electromagnetic interference and can withstand extreme conditions, including high temperature, 高圧 (tens of megapascals or above), as well as strong impacts and vibrations. It can accurately measure environmental parameters of the wellbore and well site. 同時に, fiber optic sensors with distributed measurement capabilities can measure the spatial distribution of the measured area and provide profile information. さらに, fiber optic sensors have a small cross-sectional area and occupy very little space in the wellbore.

The point type fiber optic sensor and distributed sensor used for oil logging both use a section of optical cable buried in the testing oil well. The difference is that the former sensor is an FBG connected to the end of the optical cable, while the latter is the optical cable itself. If we ignore these differences and only consider the requirements of logging technology for the optical cable itself, the two are the same, つまり, we need to consider the impact of the optical cable’s resistance to high temperature, 高圧, high corrosion, high hydrogen environment, and large length vertical deployment. The structure of optical fiber composite overhead ground wire (OPGW) used in power systems provides inspiration for designing logging optical cables.

In the structure of logging optical cables, the use of sealed units welded with stainless steel strips provides favorable protection for the optical fibers. Considering the large length of vertical distribution and the high temperature environment of oil wells, it is no longer possible to use filling composites in the steel pipes. Oil paste fillers are no longer necessary in this structure and purpose of optical cables. Only the problem of fixing the position of the optical fibers in the pipes needs to be considered, and materials such as high-temperature resistant yarns can be used to assist in positioning. The galvanized steel wire in the optical cable structure not only provides necessary strength, but also has the characteristics of corrosion resistance and high temperature resistance (short-term 400 ℃).
Fiber optics in sensing optical cables
現在, the optical fibers used for sensing optical cables are generally multimode fibers. The temperature sensing system for cables and highway tunnels typically operates at temperatures not exceeding 70 ℃ under normal operating conditions, and can use ordinary communication multimode optical fibers. The optical cable used for oil logging generally operates at a high temperature, with some oil wells reaching temperatures above 400 ℃. しかし, ordinary optical fibers coated with acrylic resin have a maximum operating temperature of no more than 100 ℃. このような状況下では, high-temperature resistant optical fibers must be used.