Formation temperature estimation by inversion of borehole measurements, Part II: Effects of fluid penetration on bottom‐hole temperature recovery

Using nonlinear inverse techniques, we show that the change in borehole temperature with time, after mud circulation has stopped, can be used to provide very precise estimates of true formation temperatures and of mud temperature at the time circulation stopped. In addition, ruggedly stable estimates can also be made of the thermal invasion distance, the formation thermal conductivity, and the efficiency of heating the mud by the thermal recovery wave. It is well known that convective heat flow into (or out of) the formation influences the thermal recovery. We show that the flow rate at the borehole can also be obtained approximately from the borehole temperature measurements using the inverse method. Fidelity and reproducibility of the inverse procedure arc examined using synthetic data. Applications to field data from three wells in the Cooper basin of Australia and four wells in the North Sea confirm the accuracy of the method in satisfying the observed data, in determining true formation temperatures, and in assessing the magnitude of fluid penetration into the formation.

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Estimation of formation temperature from bottom‐hole temperature measurements: COST ♯1 well, Norton Sound, Alaska

Geophysics ◽

10.1190/1.1442447 ◽

1988 ◽

Vol 53 (12) ◽

pp. 1619-1621 ◽

Cited By ~ 8

Author(s):

S. Cao ◽

C. Hermanrud ◽

I. Lerche

Keyword(s):

Thermal Conductivity ◽

Numerical Method ◽

Time Scale ◽

Efficiency Factor ◽

Diffusion Time ◽

Formation Temperature ◽

Temperature Estimation ◽

Bottom Hole ◽

Free Parameters ◽

Borehole Temperature

We recently developed a numerical method, the Formation Temperature Estimation (FTE) model, to determine formation temperatures by inversion of borehole temperature (BHT) measurements (Cao et al., 1988a). For more than two BHT measurements, the FTE model can estimate (1) true formation temperature [Formula: see text], (2) mud temperature [Formula: see text] at the time the mud circulation stops, (3) thermal invasion distance R into the formation before the formation is at the true formation temperature, (4) formation thermal conductivity K perpendicular to the borehole, and (5) efficiency factor F for mud heating in the borehole after mud circulation has stopped. The method optimizes three free parameters: τ (diffusion time‐scale), ε (scaling parameter related to the thermal invasion distance R), and [Formula: see text] (normalized efficiency factor for mud heating.

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Post Well Vibration Analysis in the North Sea: A Tool to Understand Drilling Performance

Volume 10: Petroleum Technology ◽

10.1115/omae2015-42227 ◽

2015 ◽

Cited By ~ 4

Author(s):

M. F. Al Dushaishi ◽

R. Nygaard ◽

E. Hoel ◽

S. Hellvik ◽

M. Andersen

Keyword(s):

North Sea ◽

Vibration Damping ◽

Rate Of Penetration ◽

Drill Stem ◽

The North ◽

Drilling Performance ◽

Bottom Hole ◽

Bottom Hole Assembly ◽

The North Sea ◽

The Impact

Severe drill stem vibrations could leads to excessive damage to the bottom hole assembly causing an increase in nonproductive time. Different drill stem vibrations models are used to predict and avoid resonance regions by optimizing the selection of bottom hole assembly components and operating parameters such as weight on bit, and surface RPM. In addition to avoid the resonance regions, specialized tools have been developed to reduce vibrations. However a complete understanding on how to mitigate vibration and its effect on drilling performance is still lacking. This study investigates the cause of drill stem vibrations, its effect on drilling performance, and the effect of including vibration reductions tools in the bottom hole assembly design in several recent drilled wells in the North Sea. Vibration damping tools used in this study were able to reduce both lateral and torsional drill stem vibration compared to a well with no vibration damping tool. Torsional drill stem vibrations tend to increase through rich sand zones causing an increase in lateral vibrations. The impact drill stem vibrations have on drilling performance was identified through rate of penetration. As lateral vibration intensity increases, instantaneous rate of penetration decreases.

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Long-offset time-lapse seismic: Tested on the Valhall LoFS data

Geophysics ◽

10.1190/1.3536640 ◽

2011 ◽

Vol 76 (2) ◽

pp. O1-O13 ◽

Cited By ~ 6

Author(s):

Hossein Mehdi Zadeh ◽

Martin Landrø ◽

Olav Inge Barkved

Keyword(s):

Synthetic Data ◽

Maximum Amplitude ◽

Time Lapse ◽

Velocity Change ◽

Seismic Properties ◽

The North ◽

Long Offset ◽

The North Sea ◽

Offset Time ◽

Velocity Changes

Conventional time-lapse seismic has been less successful for stiff-rock reservoir monitoring, such as carbonates. This is mainly because of the negligible time-lapse changes in the seismic properties. Therefore, we propose to use long-offset time-lapse seismic as an alternative method to estimate small velocity changes. More specifically, we monitor the maximum amplitude offset that is beyond critical offset. The properties of the maximum amplitude offset are similar to critical offset, except that they appear for longer offsets and are frequency dependent. Increased frequency reduces the gap between this offset and the critical offset. We find that the maximum amplitude offset is a function of overburden and reservoir velocity and practically independent of density. This method requires a velocity increase across the interface that is to be analyzed. This criterion usually is satisfied for stiff-rock reservoirs. Also, by long-offset acquisition, we mean typically 1 to 2 km beyond the critical offset for typical depths. The method is tested on the Valhall chalk field in the North Sea. The predicted velocity change using this method is in-line with an independent acoustic impedance study. The velocity changes quantitatively match reasonably well with the synthetic data.

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Attenuation of free-surface multiples by up/down deconvolution for marine towed-streamer data

Geophysics ◽

10.1190/geo2010-0337.1 ◽

2011 ◽

Vol 76 (6) ◽

pp. V129-V138 ◽

Cited By ~ 15

Author(s):

Mariusz Majdański ◽

Clément Kostov ◽

Ed Kragh ◽

Ian Moore ◽

Mark Thompson ◽

...

Keyword(s):

Free Surface ◽

Field Data ◽

Near Field ◽

Synthetic Data ◽

Ocean Bottom ◽

The North ◽

The North Sea ◽

Marine Seismic ◽

Streamer Data ◽

Multiple Elimination

Free-surface-related multiples in marine seismic data are commonly attenuated using adaptive subtraction of the predicted multiple energy. An alternative method, based on deconvolution of the upgoing wavefield by the downgoing wavefield, was previously applied to ocean-bottom data. We apply the deconvolution method to towed-streamer data acquired in an over/under configuration. We also use direct arrival deconvolution that results in source wavelet designature only, as a benchmark to verify the full multiple deconvolution result. Detailed synthetic data analysis, including sensitivity tests, explains each data processing step and its effects on the final result. We then apply this verified preprocessing sequence to field data from the Kristin area of the North Sea, with a focus on the direct arrival prediction using the near-field hydrophone method. Prestack evaluation of the results shows that the method applied to the field data provides designature, source-side deghosting, and attenuation of multiples. We show comparable stacked results from our method and from 2D iterative surface-related multiple elimination. The workflow has the benefit that it does not require an adaptive subtraction step or iterative application. However, an accurate direct arrival prediction is essential for the successful application of the method. This prediction is obtained using near-field hydrophone measurements that can be recorded with some commercial acquisition systems.

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