Category: Technical Papers

27 Sep 2013

Dual-Well 3D VSP in Deepwater Made Possible by DAS

Summary

In late 2012, we acquired a 3D Distributed Acoustic Sensing (DAS) VSP simultaneously in two injector wells in a deepwater field. We utilized seismic shots from a concurrent OBN campaign and pre-existing fiber optic cables (installed on tubing for unrelated purposes). One of the wells was mildly deviated, while the other had a complicated deviated trajectory. We obtained DAS VSP data with clear signals. The raw gathers show not only down-going P, but also PP and PS reflections, and down-going PS conversions. We also observed a surprising azimuthal phase variation in the deviated well, and some noises that underscore the importance of proper fiber connections. We conclude that 3D DAS VSP can be acquired safely and successfully in multiple deepwater wells where fiber optic cable has been installed, including wells inaccessible to geophones.

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12 Sep 2013

DAS 3D VSP in Deepwater

Oil Field Services

Mateeva, A., Mestayer, J., Yang, Z., Lopez, J., Wills, P., Roy, J. and Bown, T., ‘Dual-Well Massive 3D VSP in Deepwater made possible by DAS’, Pages 5062-5066, SEG Annual Meeting, Houston, September 2013

Link

26 Mar 2013

Fiber Optic Sensing for Improved Wellbore Surveillance

Abstract

Fiber Optic (FO) sensing technology is an exciting and novel technique offering many advantages over traditional wellbore surveillance methods1-3. Multiple FO cables can be installed that can be designed for sensitivity to a wide variety of signals such as temperature, pressure4-5, strain6-7, sound8, and the presence of specific chemical compounds. Permanently installed FO cables enable a cost effective surveillance policy where data acquisition surveys can be conducted without well interventions, in real-time, at any time, and continuous along the entire well bore. The avoidance of well intervention eliminates production deferment and operational risks of conventional surveys. Frequent, time-lapse FO based surveys can provide critical reservoir surveillance data for production and recovery optimization.

One instance of fiber-optic surveillance is Distributed Sensing, which uses the entire fiber as a sensing element. Recently, very good progress has been made in Distributed Acoustic Sensing (DAS) for hydraulic fracturing monitoring9, production profiling for commingled oil and gas producers, injection profiling for water injectors10, gas lift monitoring and the acquisition of wellbore seismic data such as Vertical Seismic Profile (VSP) surveys11-12. These applications are also seen to benefit from integration with other methods such as Distributed Temperature Sensing (DTS) and Distributed Pressure Sensing (DPS).  In terms of wellbore surveillance, the possibility to monitor flow along the entire wellbore from FO sensing provides useful insights in the complex flow behavior in a well which can be used to optimize well performance.

There are also many improvements to be made in the enabling Distributed Sensing infrastructure such as the handling and evaluation of very large data volumes and seamless FO data transfer, the robustness & cost of the FO system installation, and the overall integration of FO surveillance into the full workflows.  It will take some time before all these issues are addressed but it is clear that FO based applications will play a key role in future well and reservoir surveillance.

In this paper some examples of using DAS for Production Allocation are discussed.

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16 Nov 2012

Advances in Distributed Acoustic Sensing for VSP

Oil Field Services

Mateeva, A., Mestayer, J., Cox, B., Kiyashchenko D., Wills, P., Lopez, J., Grandi, S., Hornman, K., Lumens, P., Franzen A., Hill, D., Roy J.,  ‘Advances in Distributed Acoustic Sensing (DAS) for VSP’, SEG Expanded Abstracts Vol. 30, 4253 – 4257, SEG Annual Meeting, Las Vegas, Nevada, November. 2012

Link

10 Nov 2012

Advances in DAS for VSP

Summary
Last year we introduced Distributed Acoustic Sensing (DAS) as a new method for VSP acquisition. In DAS, an optical fiber along the borehole serves as a seismic receiver array. The fiber is interrogated by a special device at the surface, sometimes referred to as lightbox. Improvements to the interrogator unit over the past year helped DAS data to approach the utility of conventional VSP data. We show results from various field trials that demonstrate the usability of DAS for typical VSP applications such as checkshots, imaging and time-lapse monitoring. We conclude that DAS would enable VSP, and cost-effective time-lapse VSP, in a broad variety of wells, particularly those inaccessible by geophones.

Click here to download the complete technical paper.