Distributed Acoustic Sensing (DAS) for the Oil & Gas Sector

Helios DAS from Fotech converts an optical fibre, up to 40km long, into tens of thousands of individual and real-time vibration sensors. Real-time detection of the vibrations caused by acoustic disturbance at each point along the fibre is revolutionising Oil & Gas exploration, production and delivery.

 
To date Helios DAS has successfully enhanced operations by improving accuracy of understanding and therefore reducing wasted effort in a number of key activities, including:
  • Hydraulic Fracturing (Fraccing): Instant evaluation of fracturing success zone-by-zone
  • Borehole Seismic: Data obtained without well intervention or shut-in, using fewer resources 
  • Gas-Lift: Monitoring valve performance – directly & in real time, enabling planned maintenance
  • Flood Front Monitoring: Maximise recovery rates and optimize production. 
  • Leak Detection: Detect leaks early and accurately – minimise disruption & cost.

  • The Fotech Helios Distributed Acoustic Sensing (DAS) system gives the Production or Reservoir Engineer a new set of tools, which substantially removes the guesswork from the development of optimum production, and helps mitigate some of the challenges that develop in any reservoir over time. By listening to the whole well simultaneously, DAS acoustics can record, provide data and interpretative tools that have not been possible until now. With many and varied applications, the same DAS data may be used in various ways. Having a huge array of what are effectively microphones from the top of the well to the bottom, gives the fibre enabled intelligent well huge advantages over the conventional well. Helios DAS data enables the engineer to effectively visualize and record what’s going on down hole, in real time, and with much more clarity than has ever been seen before, creating value by decreasing wasteful time and effort, and ultimately, increasing recovery.
  • In a standard fracturing operation (a frac job or fraccing), each potential production zone in the well is separately exposed to the fraccing fluid conveyed at high pressure through perforations, open sleeves or other methods. Conventional design of a fracturing operation pumps a certain volume of fluid, at pressure, into the well, directed specifically at the zone to be fractured and only this zone. In each separate production zone there are only so many perforations, or a limited area of borehole, that are open to the frac fluid at any one time. Read More

     

     
  • At the present time, to obtain a borehole seismic survey on a production well, there would have to have an well intervention, probably using wireline conveyed geophones. Shutting the normal well operations down and depressurising the fluids within, making it safe for intervention operations, is a costly procedure. Helios DAS Borehole Seismic can be obtained without intervention and without shutting the well down.
    It may be necessary, with a small aperture geophone string, to shoot into a short depth interval of the well from a positioned surface source, stacking multiple shots, before moving the downhole tool up to the next section of well covered by the aperture of the tool. This process is repeated until a substantial part of the well is covered by the survey. Alternatively, with a moving source and a small aperture geophone array, only a small area of the target reservoir may be illuminated. Read More
  • By using Fotech’s Helios DAS sensing capabilities it is possible to watch, directly in real time, how gas lift valves are performing within the well. Unloading the well using gas lift necessitates each gas lift valve to progressively operate in proper order and at the right time. Often not monitored directly at source, there are gas lift issues that can be recognised and dealt with in real time reducing response time and increasing efficiency. Directly monitoring gas lift valves allows the completions engineer to optimize the gas flow used to lift and optimize the effective fluid flow that is obtained from gas lifting. Read More
  • The benefits of using Helios DAS to detect fluid leakage either from the well to the formation or within casing annuli, means that detection and recognition can be made earlier when the leak is smaller and the damage, or danger, having less serious consequences.

    By identifying the depth, substantially quantifying and likely determining the reason for that leakage, in real time, there is likely to be less reason for a separate intervention in the well, just to identify the leak site. Read More

  • In planned water, steam or other type of floods, the interface between the produced fluid and the flood fluid is desired to be regular and linear if at all possible. The flood control parameters are designed to push the desired fluids ahead of the flood in a smooth and efficient manner, so that there is a minimum of produced fluids left behind.
    It is desirable that the flood fluids do not progress toward the producing well in an uneven manner. Uneven floods may form isolated pockets of unproduced fluids. The flood front may be imagined simply as a two dimensional surface, interfacing the two fluids, progressing evenly from the injection wells to the production wells, through the interstitial spaces in the formation, sweeping the production fluids before it. This could be implemented in a linear or expanding circular progression, depending on the application or reservoir. Read More