Measurements of Streaming Potential for Downhole Monitoring in Intelligent Wells
Figure 4: Vertical Cross-section Through a 3D Reservoir Model Showing the Streaming Potential (in Volts) Throughout the Reservoir Layer
AB 0.06
0.01
Uncertainties in the Interpretation of Streaming Potential Measurements
CD
0.0 0.19
0.0 0.03
0.0 -300 -200 -100 0
Distance from well (m)
The position of the waterfront is marked by a solid black line.
A and C: Potentials for a homogeneous model with the waterfront at 300 and 100m from the well, respectively. B and D: Potentials from the model with high permeability in the lower part of the reservoir with the waterfront at 300 and 100m from the well, respectively.
Figure 5: Streaming Potential Measured at the Well versus Depth for a Heterogeneous Reservoir Model with the Waterfront Far (80m) from the Well (A) and at the Well (B)
590 580 570 560 550 540 530 520 510 500
600
01 Potential (mV)
2 A
590 580 570 560 550 540 530 520 510 500
600
02 Potential (mV)
4
The high-permeability layer at the base of the reservoir is shown in grey. The encroaching water exploits the high-permeability layer, leading to a change in the streaming potential profile measured at the well.
towards the top of the high-permeability layer, in line with the location of the water. The streaming potential measured along the length of the well therefore reflects the shape of the encroaching waterfront, which suggests that waterfront geometry could be determined using an array of electrodes installed along the well. This information could be used to inform a proactive inflow control strategy.
1. Algeroy J, Morris AJ, Stracke M, et al., Oilfield Review, 1999;11(3):18–29.
2. Glandt CA, SPE Drilling & Completion, 2005;20(4):281–8.
3. Addiego-Guevara EA, Jackson MD, Giddins MA, SPE/DOE Symposium on Improved Oil Recovery, Tulsa, Oklahoma, 20–23 April 2008.
4. Robison CE, Paper SPE 38497 presented at the 1997 Offshore Europe Conference, Aberdeen, Scotland, 9–12 September 1997.
5. Kharghoria A, Zhang F, Li R., et al., European Petroleum Conference, Aberdeen, United Kingdom, 29–31 October
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2002.
6. Jansen JD, Wagenvoort AM, Droppert VS, et al., SPE Asia Pacific Oil and Gas Conference and Exhibition, Melbourne, Australia, 8–10 October 2002.
7. Mjaaland S, Wulff A-M, Causse E, et al., Society of Petroleum Engineers Annual Technical Conference and Exhibition, Dallas, 2000.
8. Bryant ID, Chen M-Y, Raghuraman B, et al., SPE Drilling &
Completion, 2004;19(4):253–64.
9. Saunders JH, Jackson MD, Pain CC, Geophysical Research
Letters, 2006;33:L15316.
B
To date, streaming potential signals have been measured in the subsurface during transient injection and production tests,11
but have
not yet been interpreted to determine the location of an encroaching waterfront for proactive inflow control. A method to interpret the signals and close the loop between monitoring and control is still under development.
Conclusions
Streaming potential measurements are a promising method for downhole monitoring in intelligent wells. Water encroaching on a production well equipped with permanently installed electrodes causes changes in the measured streaming potential, which could be resolved above background electrical noise; indeed, water could be detected and monitored while it is several tens to hundreds of meters away. This contrasts with most other downhole monitoring techniques, which sample only the formation immediately adjacent to the wellbore.
These findings raise the novel prospect of an oilfield in which wells can detect the approach of water and respond appropriately to control inflow in a proactive feedback loop. Such wells offer enormous potential economic and environmental benefits, particularly in fields that are difficult to access or dangerous to operate. However, there are still significant uncertainties to be resolved before the measurements can be interpreted with confidence, and the method has not yet been successfully implemented in a real field trial. n
10. Saunders JH, Jackson MD, Pain CC, Geophysics, 2008;73(5):E165–E180.
11. Chen MY, Raghuraman B, Bryant ID, 2006 SPE Annual Technical Conference and Exhibition, San Antonio, Texas, 24–27 September 2006.
12. Hunter RJ, Academic Press, New York, 1981. 13. Jaafar MZ, Vinogradov J, Jackson MD, et al., 2009 SPE Middle East Oil & Gas Show and Conference Bahrain, 15–18 March 2009.
14. Jackson MD, J Geophys Res, 2008;113:B04201.
During multiphase flow, the magnitude of the coupling coefficient decreases with decreasing water saturation, but the exact nature of the relationship is still poorly understood. This is particularly the case in oil- wet and mixed-wet reservoirs in which the nature of the electrical double layer at oil–mineral interfaces and at the oil–water interface must be quantified.14
100 0.0 -300 -200 -100 0
Distance from well (m)
100
There are still significant uncertainties associated with the interpretation of streaming potential measurements, particularly concerning the magnitude of the streaming potential coupling coefficient. As salinity increases, the magnitude of the coupling coefficient decreases and, until recently, was predicted to fall to zero at seawater salinity. If this were the case, streaming potential signals would be very small or even zero in most hydrocarbon reservoirs. However, new experimental data show that the coupling coefficient does not drop to zero at seawater salinity, but continues to decrease gradually until it reaches the saturation limit. Streaming potential signals should therefore be measurable and interpretable in most hydrocarbon reservoirs.13
EXPLORATION & PRODUCTION – VOLUME 8 ISSUE 1
Depth (m)
600
Depth (m)
500 600
Depth (m)
500
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