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RMS Amplitude Dominant Frequency Dip Deviation Reflection parallelism Subset • • • • Initialize • • • Neural Network Training RMS Amplitude + Dom. Frequency + Refl. Intensity + Variance • • Classify • • -1372 -1422 Additional interpretive feature • • Seismic Facies Result ‣ ‣ ‣ ‣ ‣ Subject to endorsement by TRLC Internal Open
Fiber optic distributed acoustic sensing (DAS) acquisition technology is used to continuously monitor production and seismic data along the entire well and obtain better seismic images. DAS utilizes fiber optics to permanently place receivers uniformly every 8m along the entire wellbore without the need for well intervention. The typical method to monitor production data typically utilizes localized sensors which are placed non-uniformly along the borehole. Borehole seismic data or Vertical Seismic Profiling (VSP) data is usually acquired through a well intervention procedure to allow receivers to be lowered down the borehole at larger, 15-20m intervals. Conventional VSP data is also more expensive since well intervention means loss of production for the entire duration of the acquisition. The typical production monitoring method does not provide continuous data across the borehole since conventionally used sensors such as Pressure Downhole Gauges (PDGs) are only placed at zones of interest. To mitigate these issues, DAS is utilized to continuously record production and VSP data at shorter intervals across the entire wellbore trajectory. Left: Conventional VSP method. Localised receiver location. Sparser receiver spacing. Limited azimuth coverage 2 . Right: DAS VSP method. Continuous receiver locations. Denser receiver spacing. Better azimuth coverage 2 . Top: Seismic source vessel. Bottom: GPS receivers installed on the Bokor platform. It is used to time stamp the DAS raw field data based on the GPS data. Left: Seismic data shows the Bokor field distorted by shallow gas cloud (red circle) 3 . No useful information is available for interpreters. Right: DAS VSP data overlaid on Bokor’s seismic data shows better resolution and lateral continuity under the gas cloud region 3 . Light signal is sent down the wellbore through fiber optics. Receivers are placed all along the wellbore to obtain production and seismic data. Results of DAS. Top: Production monitoring data. Bottom: Seismic data Gas lift at particular depth and time is highlighted 3 . Light signal is sent down the wellbore via an interrogator unit (I/U). The I/U consists of the laser and detector component. It sends pulses of light via laser. Seismic events represented by the blue dialogue bubble is recorded and reflected back to the I/U via Rayleigh backscatter 1 . Operations Geophone VSP Requirement to shut in well and lower tools. More expensive and less safe. DAS VSP No interference with well operations. Uses existing fiber. Cheaper and safer. Data quality 3C, good SNR. Directionality, poor SNR need production zones. Repeatability Possible, but cost is prohibitive. Always available for repeat (4D) measurements. Cheaper. Borehole Coverage Restricted. 100% of borehole. The interrogator unit (I/U) shown above transmits and processes light signal sent down the wellbore. One I/U is required per well. For Bokor, data were acquired from five wells. Tapes record the production monitoring and seismic data. The GPS unit stamps the raw field data with time stamps. The interrogator unit meanwhile consists of the laser and detector components. Collaboration with Multimedia University and Optasense for R&D into omni directional optical fiber sensors. Collaboration with Delphi Consortium for integrated surface and borehole seismic high resolution imaging development. Location and well trajectory of the wells in Bokor that were selected to obtain DAS VSP data. From left is well BO-122, BO-125 followed by BO-124. 1. Dria, D. (2012), E&P Applications of Fiber Optic Technologies. In: Distinguished Lecture Program. [online] SPE. Available at: http://www.spe.org/dl/docs/2012/dria.pdf [Accessed 14th Oct. 2016]. 2. Hornby, B.E., Yu, J., Sharp, J.A., Ray, A., Quist, Y., and Regone, C., (2006). VSP: Beyond time-to-depth. The Leading Edge, pp. 446-452. 3. Optasense (2016), Production monitoring and VSP at Bokor internal reports for P<strong>ET</strong>RONAS. Kuala Lumpur: Optasense Subject to endorsement by TRLC Internal
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