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Pore Pressure Calculation with Extensive Focus on Seismic Prediction Techniques

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thesis mop

on 10 February 2014

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Transcript of Pore Pressure Calculation with Extensive Focus on Seismic Prediction Techniques

Pore Pressure Prediction
Objective
Research
Application
Analysis
?
What is Pore Pressure
Pore Pressure
Importance ?
Over burden stress
Effective vertical stress
Compaction Trends
Over Burden
Pressure

Effective
Stress

Pore Pressure
-
Via Bulk Density
Pre-Drilling
While Drilling
Post-Drilling
Logs
Sonic Logs
Pore Pressure Detection
Pore Pressure prediction
Seismic process
Gather
Interpret
Process
D-exponent
Building the story
Decipher the code
NMO
Data Acquisition
www.pnronline.com.au
50 % of well kicks is due to improper pore pressure prediction.
http://coastal.er.usgs.gov/gc-subsidence/slide-show/img007.jpg
chuma.cas.usf.edu
Pore Pressure
J.zhang/sciencereviews108(2011)
Normal Compaction Trend
Abnormal Compaction Trend


Using Density Logs Directly
Using Seismic
RFT
Well Logs
D-exponent
J.zhang/sciencereviews111(2011)
Logs
Resistivity Logs
http://img.tjskl.org.cn/pic/z1a5de34-0x0-1/5810ha_repeat_formation_tester_rft.jpg
Zhang, Jincai. Schematic resistivity. 2011. Pore pressure prediction from well logs pg. 56.
Zhang, Jincai. Schematic resistivity. 2011. Pore pressure prediction from well logs pg. 56.
http://blogs.bakerhughes.com/reservoir/files/2011/03/ft.jpg
Yully p. Solano p.108 (2007)
(Oyvind kvan, Pore Pressure Prediction from seismic data sets, 2005)
24% of NPT is due to false pore pressure prediction.
(J.Zhang, Pore Pressure Prediction from well logs, 2011)
Case
Study
lagia
Well information
Lagia 8 in Sinai
D-exponent
Resistivity
Sonic
Theory
Theory
Eaton's Resistivity
Theory
Eaton's sonic
CMP stacking
Migration
http://folk.uio.no/ftsikala/mjolnir/photo_gallery/gif/seis_profiles.gif
Dutta, N. C., 1987, Shale compaction and abnormal pore pressuures 53rd Ann Internat
References
Bowers, G.L., 1995. Pore pressure estimation from velocity data; accounting foroverpressure mechanisms besides undercompaction. SPE Drilling and Completions,June, 1995, pp. 89–95.
Compaction and Cementation. (n.d.). Retrieved from The Geological Society: http://www.geolsoc.org.uk/ks3/gsl/education/resources/rockcycle/page3559.htmlDix, C. H., 1955, Seismic velocities from surface measurements:Geophysics, 20, 68–66.
Dutta, N. C., 1987, Shale compaction and abnormal pore pressuures: A model of geopressures in the Gulf Coast Basin: 53rd Ann. Internat.Eaton, B.A., 1968.
Fracture Gradient Prediction and Its Application in Oilfield OperationsPaper SPE2163 JPT 25–32.
Elphick, Robert Y., 1991Determining Geopressures From Resistivity LogsGeobyte (published by AAPG), April, 1991, p. 48 – 58
Fang, W.W., Langseth, M.G., and Schultheiss, P.J., 1993
Hottmann, C.E., Johnson, R.K., 1965. Estimation of formation pressures from log-derivedshale properties Paper SPE1110 JPT 17, 717–722.
Gardner, L.W., Gregory, A.R., 1974. Formation velocity and density the diagnostic basis for stratigraphic traps. Geophysics 39 (6), 2085–2095.
Matthews, W. R., and Kelly, J., 1967How To Predict Formation Pressure And Fracture GradientOil and Gas Journal, v. 65, February 20, 1967, pp. 92 – 1066
Mavko, G. (2009). The Rock Physics Handbook; Tools for seismic analysis of porous media. Cambridge.
Miller, T.W., 1995New Insights On Natural Hydraulic Fractures Induced By Abnormally High Pore Pressure
http://www.sandmeier-geo.de/images/wwb_img33.jpg
http://www.geophysics.net/image545
http://www.geophysics.net/image578
Terzaghi's Equation:
Pore Pressure evaluation From well logging with Extensive Focus on Seismic Prediction Techniques at LAGIA-8 well, Sinai, Egypt.
A.Z.NOAH
Faculty of Science and Engineering, The American University in Cairo

Pore Pressure evaluation From well logging with Extensive Focus on Seismic Prediction Techniques at
LAGIA-8 well, Sinai, Egypt.
A.Z.NOAH
Faculty of Science and Engineering, The American University in Cairo



Pressure prediction from seismic data has two major components: a rock model that relates effective stress to velocity, and the velocity field. The errors in the predicted pressure arise from both sources. It is true that even if the rock model were perfect—an unlikely case—there would still be errors in the predicted pore pressure due to inherent errors in the seismic velocity field. Drilling experience has indicated that when seismic velocities are processed and conditioned as outlined in this paper, one can obtain pressures to within 0.50 ppg at target depths in the deepwater, provided that the low- frequency trends in the seismic interval velocity curves are of good quality and lie within 5–10% of well velocities. However, seismic velocities still lack resolution, even when including the high-frequency components provided by various inversion methodologies. Quite often, pressure regressions within thin overpressured sands and shales (thickness less than a quarter wavelength of the dominant frequency of seismic waves) are not detected by seismic techniques prior to drilling. This can result in expensive downtime. At present, there still is no consistently reliable methodology to predict the occurrence of such an event.

Pore pressure from seismic
Log analysis is a common procedure for pore pressure estimation in both off-set wells and the actual well drilling. New measurement while drilling (MWD) tools implement log analysis techniques in real time drilling mode.
The resistivity log was originally used for pressure detection. The log response is based on the electrical resistivity of the total sample, which includes the rock matrix and the fluid-filled porosity. If a zone is penetrated that has abnormally high porosities ( at the same time high pressure) the resistivity of the rock will be reduced due to the greater conductivity of water than rock matrix. Since the high formation pressures were originally developed in shale sections and later equalized the sand zone pressures, only the clean shale sections are used as plotting points. This excludes sand resistivities, silty shale, lime and any other type of rock that may be encountered. As the shale resistivities are selected and plotted, a normal trend line should develop prior to entry into the pressured zone.

Pore pressure from logs
Finally comparing the values of pore pressure from both Seismic and Well logging , it was found that these value show coincidence
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