Near-wellbore Alteration and Formation Stress Parameters using Borehole Sonic Data

Sinha, Bikash K.; Bratton, Tom; Cryer, Jesse V.; Nieting, Steve; Ugueto, Gustavo; Bakulin, Andrey; Hauser, Matt R.

doi:10.2118/95841-ms

Cited by 16 publications

(12 citation statements)

References 15 publications

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“…3, the formation shear may be estimated using a elastic model based inversion; 24 such a model is incompatible with the stress induced anisotropy in this study. While it is possible to invert the data from our experiment for more detailed information about the state of stress in the formation, 25,26 in this report we focus on extracting the far field shear slowness values in these two orthogonal directions using a parametric inversion technique. 17 This parametric inversion uses the following Bessel functions to describe a measured dipole dispersion curve with four free parameters: S 0 , S 1 , a, and b:…”

Section: Stress Effect On Tube Modementioning

confidence: 99%

Experiments on stress dependent borehole acoustic waves

Hsu

Kane

Winkler

et al. 2011

The Journal of the Acoustical Society of America

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In the laboratory setup, a borehole traverses a dry sandstone formation, which is subjected to a controlled uniaxial stress in the direction perpendicular to the borehole axis. Measurements are made in a single loading-unloading stress cycle from zero to 10 MPa and then back down to zero stress. The applied stress and the presence of the borehole induce anisotropy in the bulk of the material and stress concentration around the borehole, both azimuthally and radially. Acoustic waves are generated and detected in the water-filled borehole, including compressional and shear headwaves, as well as modes of monopole, dipole, quadrupole, and higher order azimuthal symmetries. The linear and non-linear elastic parameters of the formation material are independently quantified, and utilized in conjunction with elastic theories to predict the characteristics of various borehole waves at zero and finite stress conditions. For example, an analytic theory is developed which is successfully used to estimate the changes of monopole tube mode at low frequency resulted from uniaxial stress, utilizing the measured material third order elasticity parameters. Comparisons between various measurements as well as that between experiments and theories are also presented.

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Section: Stress Effect On Tube Modementioning

confidence: 99%

Experiments on stress dependent borehole acoustic waves

Hsu

Kane

Winkler

et al. 2011

The Journal of the Acoustical Society of America

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“…So, accurate and reliable estimation of horizontal stress magnitudes can provide an early warning of impending drilling problems that may be mitigated by appropriate drilling fluid design and drilling practices (Sinha et al 2008). From the available well log data and estimated PP data for the five wells are next used to estimate the in situ stress.…”

Section: Analysis Of In Situ Stress In Offshore Wellsmentioning

confidence: 99%

Overpressure zone under the Krishna–Godavari offshore basin: geophysical implications for natural hazard in deeper-water drilling

2010

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Accurate knowledge of pore pressure is fundamental to any safe and economic well construction. Here, we present results that are indicative of over pressure zones (OPZ) for five wells drilled under the Krishna-Godavari offshore basin (KGOB) at the Eastern Continental Margin of India (ECMI). OPZ in areas of crustal flexuring can act as potential geohazard while drilling. These wells locate at water depths of 515-1,265 m, where their penetrated-vertical-depth reaches up to 3,960 m in clastic sediments. pore pressure gradient (PPG) and fracture pressure gradient (FPG) are estimated from acoustic log for all five wells, while the Normal Compaction Trend (NCT) and pore pressure are calculated from Miller's sonic equation. Top of OPZ is indicated by values that are higher than the NCT; departure from NCT is observed at depth intervals of 1,320-2,180 m, 1,700-3,960 m, 1,600-1,880 m, 1,420-2,609 m and 2,080-2,200 m for the respective Wells 1 through 5. The pressure data from Modular Dynamic Tester (MDT) agree well with the pore pressure values obtained from the logs. The Overburden Gradient (OBG), PPG and FPG values increase rather slowly with total depth in deeper-water of KGOB when compared to the wells located in shallow water depth. Consequently, the operating safety margin between PPG and FPG decreases as the water depth increases, and this clearly leads to an increase in the number of casing strings to reach the target depth. Certain basic conclusions on the potentiality of natural hazard for drilling operations are drawn on the basis of these results, but evidently, further studies are warranted to present a more composite picture of OPZ under KGOB.

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“…Identifying horizontal stress directions and magnitudes is also crucial for well design and minimizing wellbore instability problems. Several methods can be used to identify horizontal stress directions including caliper data, image logs, microseismic monitoring, 3-component vertical seismic profile (Plona et al, 2002), and full waveform acoustic data (Sinha et al, 2008).…”

Section: Full Waveform Acoustic Data Analysismentioning

confidence: 99%

Full waveform acoustic data as an aid in reducing uncertainty of mud window design in the absence of leak-off test

Aghajanpour

Fallahzadeh

Khatibi³

et al. 2017

Journal of Natural Gas Science and Engineering

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Creating a mechanical earth model (MEM) during planning the well and real-time revision has proven to be extremely valuable to reach the total depth of well safely with least instability problems. One of the major components of MEM is determining horizontal stresses with reasonable accuracy. Leak-off and minifrac tests are commonly used for calibrating horizontal stresses. However, these tests are not performed in many oil and gas wellbores since the execution of such tests is expensive, time-consuming and may adversely impact the integrity of the wellbore. In this study, we presented a methodology to accurately estimate the magnitudes and directions of horizontal stresses without using any leak-off test data. In this methodology, full waveform acoustic data is acquired after drilling and utilized in order to calibrate maximum horizontal stress. The presented methodology was applied to develop an MEM in a wellbore with no leakoff test data. Processing of full waveform acoustic data resulted in three far-field shear moduli. Then based on the acoustoelastic effect maximum horizontal stress was calibrated. Moreover, maximum horizontal stress direction was detected using this methodology through the whole wellbore path. The application of this methodology resulted in constraining the MEM and increasing the accuracy of the calculated horizontal stresses, accordingly a more reliable safe mud weight window was predicted. This demonstrates that the presented methodology is a reliable approach to analyze wellbore stability in the absence of leak-off test.

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Near-wellbore Alteration and Formation Stress Parameters using Borehole Sonic Data

Cited by 16 publications

References 15 publications

Experiments on stress dependent borehole acoustic waves

Experiments on stress dependent borehole acoustic waves

Overpressure zone under the Krishna–Godavari offshore basin: geophysical implications for natural hazard in deeper-water drilling

Full waveform acoustic data as an aid in reducing uncertainty of mud window design in the absence of leak-off test

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