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Filtering and muting of the data in Fig. 5 to exclude the tube waves reveal both down-going and up-going (reflection) compressional (P) waves in the vertical section of the well.
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Distributed acoustic sensing (DAS) is a rapidly evolving fiber optic technology for monitoring cement curing, perforation performance, stimulation efficiency, and production flow and, more recently, for performing vertical seismic profiling (VSP). VSP data can be acquired and processed to determine velocity models that are used in surface seismic i...
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Context 1
... arrows at the bottom of the image. Conventional VSP products were created from the vertical portion of the well. The record shown in Fig. 5 was frequency-wavenumber (f-k) filtered to reject events propagating at the tube wave velocity. It was then further muted to isolate the down-going and reflected, up-going P wave events, which are shown in Fig. 6. The reflected P-waves are more obvious on this image than on the original because the filtering process successfully removed the unwanted events propagating at the tube wave velocity. The dense 1 m spatial sampling of the DAS data provides for unaliased tube wave signals in the f-k domain and thus ensures the possibility of filtering ...
Context 2
... this end, a corridor stack was created from the CT DAS VSP data shown in Fig. 6, which can be used to calibrate surface seismic data. The up-and down-going P waves were separated, and the multiples were removed from the up-going wave field by deconvolution with the down-going wave field. The first break arrival times of the down-going P waves were picked and used to convert the upgoing wave field to two-way time. ...
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Aiming at the problem that the layered water injection cannot be accurately obtained in the process of oilfield development, this paper proposes an optical fiber vibration signal recognition and classification algorithm based on XGBoost integrated learning. Firstly, the optical fiber vibration signal collected by the optical fiber vibration sensor is denoised by variational mode decomposition and reconstruction. Then generate spectrograms corresponding to different water absorption layers at different times. A dataset containing 3000 spectral images is obtained. The data sets are imported into support vector machine, random forest classifier and XGBoost integrated classifier based on decision tree for recognition and classification. The parameters of the obtained model are optimized and the model is evaluated by cross validation. Finally, the obtained models are compared and tested. The experimental results show that the XGBoost ensemble learning algorithm with decision tree as the base classifier can effectively identify different vibration signals. This method has a certain significance for the identification of layered relative water absorption of water injection profile.
With the development of distributed fiber optic acoustic sensing technology in the field of borehole seismic surveys, more and more oil fields choose to pre-install fiber optics in the well in advance for borehole seismic data acquisition or fluid detection. In 2022, ADNOC completed the world’s first multi-well DAS VSP and OBN joint acquisition survey in the Persian Gulf, with the fiber placed outside the tubing, relying on the offshore high-density OBN acquisition survey, completing a total of 13 wells for DAS VSP acquisition. The DAS VSP raw data spacing interval is 1 m, the sampling interval is 1 ms, and the offshore air guns are staggered at a density of 25 m × 25 m. This study will focus on the determination of multi-well DAS VSP data acquisition area, data analysis for different Gauge Length, and raw data quality control.
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Distributed Acoustic Sensing (DAS) through fiber optic has been deployed in downhole monitoring for over two decades. Several technological advancements led to a wide acceptance of this technology as a reliable surveillance technique. This paper presents a comprehensive technical review of all the applications of DAS.
The paper starts with the fundamentals of fiber optic deployment. Then, an overview of all the applications of DAS including seismic application (vertical seismic profiling), microseismic (hydraulic fracturing characterization), well and pipe integrity (such as leak detection and cement quality), and well and pipe flow monitoring is provided. Flow monitoring contains injection and production flow estimation, phase determination, gas and water breakthrough identification, gas lift surveillance, pump and flow control device performance evaluation, sand production detection, and flow regime recognition.
This paper reviews the basics of DAS, fiber types, installation methods, types of recorded data, data processing, historical development, current applications and limitations. The paper provides a concise review using several field cases from over two hundred published papers of Society of Petroleum Engineering (SPE) and journal databases. The applications of DAS in downhole monitoring can be generally divided into the qualitative and quantitative applications. The study discusses deployment methods, case by case worldwide field performance and interpretation/modeling. It also summarizes main lessons, key results, and challenges including data quality, signal to noise ratio effect, and operational conditions such as the installation of the fiber and the complexity of quantitative production prediction and flow profiling. In addition, a comparison between deployment of DAS and other methods is reviewed.
This study is the foundation for an ongoing study on wellbore and reservoir surveillance through real time distributed fiber optic sensing (DAS) records along the wellbore. It summarizes the historical development and current limitations to identify the existing gaps and reviews the lessons learned during the two decades of the application of DAS in downhole monitoring.
We briefly review the history of distributed acoustic sensing (DAS) as applied to geophysical problems over the past 20 years, including a bibliography of about 900+ DAS‐related papers and abstracts. First, we introduce some general reviews and introductory papers on DAS to provide readers with an overview of DAS technologies and their various applications. Second, we discuss geophysical applications of fiber Bragg grating (FBG) based DAS systems. We describe 10 major geophysical applications of DAS technologies based on Rayleigh backscattering systems in Part 3 of this chapter. We then share some of the open problems and promising areas of research in the hope of promoting future development of DAS as a geophysical tool.
Effective Steam Assisted Gravity Drainage (SAGD) operation relies on subcool management to reduce the risk of steam breakthrough. Monitoring of several parameters is performed to assure uniform development of steam chamber and heating of reservoir. This paper discusses the application of Distributed Acoustic Sensing (DAS), a monitoring platform to achieve reliable reservoir and wellbore surveillance in SAGD projects.
In this study, a comprehensive review of DAS deployment in oil and gas industry was performed including vertical seismic profiling, hydraulic fracturing, well/pipe integrity and flow profiling applications. Then, SAGD flow monitoring was investigated in detail. To utilize DAS in SAGD projects, knowing completion designs are necessary. Therefore, various SAGD completion designs and corresponding flow regimes were discussed as well. Finally, four flow loop designs were proposed to accurately simulate the complex wellbore hydraulics of the SAGD producer using DAS recordings.
This work started with an overview of DAS systems in downhole monitoring including real time high resolution vertical seismic profiling, hydraulic fracturing characterization and optimization, well and pipe integrity, leak detection and assessing completion effectiveness. Then, flow profiling including flow rate, flow fractions and flow regimes determinations using DAS were discussed with focus on SAGD monitoring. Completion designs directly impact on SAGD monitoring and DAS recordings, more specifically on flow regimes inside the tubing and annulus. Therefore, various completion designs with their tubing and screen sizes were presented and corresponding flow regimes were determined in both tubing and annulus. It was observed that flow regimes vary with type of completion design, liquid flow rate, steam breakthrough locations and tubing/screen sizes. Eventually, four flow loop designs were proposed based on the discussions for future DAS application.
This paper discusses existing completion designs and possible flow regimes in SAGD projects. Consequently, novel designed flow loops are introduced for DAS deployment to better understand the complex wellbore hydraulic of the well and measure the key parameters in optimizing the production operation. This study is a design stage for future quantitative measuring of flow profiling using DAS systems.
