SPE 115675

Geosteering with a Combination of Extra Deep and Azimuthal Resistivity Tools W. Hal Meyer, Eric Hart, and Kaare Jensen, Baker Hughes

Copyright 2008, Society of Petroleum Engineers This paper was prepared for presentation at the 2008 SPE Annual Technical Conference and Exhibition held in Denver, Colorado, USA, 21–24 September 2008. This paper was selected for presentation by an SPE program committee following review of information contained in an abstract submitted by the author(s). Contents of the paper have not been reviewed by the Society of Petroleum Engineers and are subject to correction by the author(s). The material does not necessarily reflect any position of the Society of Petroleum Engineers, its officers, or members. Electronic reproduction, distribution, or storage of any part of this paper without the written consent of the Society of Petroleum Engineers is prohibited. Permission to reproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied. The abstract must contain conspicuous acknowledgment of SPE copyright.

Abstract A resistivity tool with a large depth of investigation (greater than 30 meters in ideal conditions) has been designed and used in the North Sea Grane field for over three years. An azimuthal resistivity tool with a depth of detection of about 6 m in ideal conditions has now been added to the bottomhole assembly. When the deeper measurement detects a conductive zone there is no information about the direction to the target because the measurement has azimuthal symmetry. The shallower azimuthal measurement will be able to give the direction to the conductive zone when it comes within the depth of detection of the tool.

The target for this effort is a thick reservoir (about 60 meters) that has a long, gradual transition from a resistivity of about 300 ohmmeters at the top of the sand to the water zone of about 0.5 ohmmeters at the bottom. A shale formation of about 1.0 ohmmeter is found both above and below the sand. A deep resistivity tool, a normal propagation resistivity tool, and an azimuthal resistivity tool are all used to place the well in the ideal position to produce the reservoir.

The azimuthal tool has no response in a homogeneous formation. The result is a better depth of detection because the signal from the target zone does not have to be removed from a constant background signal. Unfortunately, a gradient is not a homogeneous formation and the result is a background response roughly 10 times the normal noise floor of the tool. However, the shallow measurements of the traditional axial propagation resistivity tool are used to estimate the response of the azimuthal tool to the resistivity gradient. The difference between the estimated response and the actual response is a better indication of a nearby conductive bed.

Both synthetic models and actual data are used to show how the combination of the three resistivity tools can geosteer in this complicated environment. In particular, this combination is able to distinguish between a shale body above the tool and a shale encroaching from below.

Introduction The StatoilHydro ASA operated Grane oil field is located in the Norwegian North Sea block 25/11 (Fig. 1), approximately 200 km northwest of Stavanger. The field has been in production since September 2003 and has a cumulative production of 295 million barrels of oil per May 2008.

The reservoir consists of massive Heimdal Member turbidite sandstones of Paleocene age, enclosed within the Lista Formation claystone. The predominantly fine-to-medium-grained, moderate-to-well-sorted reservoir sandstones show excellent reservoir properties with porosities of 30-33 porosity units and permeabilities typically in the 5-10 Darcy range (Helgesen et al., 2005b).

Experience has shown that shale intervals may be encountered when drilling horizontal production wells, particularly close to the reservoir base. Image data and dip calculation (based on azimuthal resistivity data) indicate that the shale intervals have steep boundaries. This suggests a post-depositional origin, associated with folds and faulting (Helgesen et al., 2005b).

The highly viscous (12 cP) biodegraded oil of the Grane field has a density of 895kg/m3, close to that of the formation water, which is 1018kg/m3. Due to the small density contrast, a very long transition zone above the oil/water contact has developed throughout the field. This transition zone is clearly defined on all resistivity logs.

The drainage strategy of the Grane field is based on gas injection at first and later water injection for pressure support. A dense pattern of 1000 to 3000 meter long horizontal producers is part of the plan (Helgesen et al., 2005b). The gas injectors are placed structurally high to push the oil down to the producers while water injectors are to be placed low, pushing cellar oil upwards. Based on reservoir simulation studies, the optimal placement of the horizontal producers was evaluated to be 9

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meters true vertical depth above the oil/water contact where a water leg exists. Where the base reservoir is expected structurally higher than the oil/water contact, the producers are placed close to the base reservoir. The small density difference between the Grane oil and the formation water causes instabilities in the oil/water contact after extensive oil production and gas injection. Gas injection may locally force the stiffer oil into the water zone. When this happens the more mobile water may be forced to spill over local basin-shaped shale topography along the base of the sandstone (Helgesen et al., 2006).

Fig. 1: Grane location off Norway in the North Sea

An extra deep propagation resistivity tool has been used to geosteer the drillstring 9 meters above the oil/water contact

(Helgesen et al., 2005a). This tool has one axial transmitter with two axial receivers spaced 12 meters and 17 meters from the transmitter. While this tool can accurately maintain the distance in the presence of the reservoir gradient, it lacks directionality, which can result in confusion when the normal gradient is interrupted by shales in the lower part of the reservoir. A tool with azimuthal sensitivity (Chemali et al., 2006) was added to the tool string to improve the geosteering capability. A diagram of the new tool is shown in Fig. 2. This tool is a normal axial propagation resistivity tool (Meyer 1994) with two fully orthogonal receivers added to yield the azimuthal readings. The red antennas are used for the azimuthal measurement; the outer two are axial transmitters and the inner two are orthogonal receivers. The two orthogonal receivers are 22 inches apart compared to eight inches for the axial receivers. All measurements have the same measure point (the center of the receivers). The outer transmitters are 36 inches from the measure point. The measurement array is symmetric.

Figure 2: Propagation resistivity tool with axial transmitters and both axial and azimuthal receivers. The red antennas are the azimuthal array with the receivers on the inside.

The advantage of the fully orthogonal array is the absence of any signal from a uniform formation. In a resistive reservoir

this array will have no response until the response of the conductive boundary exceeds the instrument noise (approximately 10 nanovolts). The tool that actually recorded the data used in our study was not integrated with the axial propagation resistivity tool, but the depths have been adjusted so that the data from both tools appear to be coincident. The azimuthal tool in Fig. 2 operates at both 400 kHz and 2 MHz, but only 400 kHz data were used in this study. The orthogonal receivers can also receive signals from the two short spaced axial transmitters, but these measurements will probably not be used in geosteering applications. Under ideal conditions (resistive reservoir and conductive shoulder bed) the depth of detection of the shoulder bed is about 6 meters regardless that the length of the array is only 2 meters. However, this reservoir does not represent ideal conditions. The gradient in the reservoir produces a signal in the azimuthal receivers which will restrict the depth of detection of the target. To improve the depth of detection, our strategy is to estimate the signal from the gradient and

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remove the estimated signal from the instrument response. This should improve both the estimate of the depth to the detected object and the direction towards it.

Expected Response on the Planned Wellpath Fig. 3 shows the transition zone resistivity gradient model for the actual boreholes analyzed in our study. The gray stair-stepped resistivity profile is the model for the transition zone (simulated using 91 layers). The depth scale is in true vertical depth. Several different gradient models are used in this field; this one is considered best for the two horizontal boreholes to be analyzed here. The measurements that are transmitted in real time in the actual resistivity surveys are all plotted as computer-simulated curves in this figure. The axial propagation resistivity curves are the 400 kHz attenuation measurement from the long-spaced array and the 2 MHz phase difference from the same array. At this scale, these two curves are hard to distinguish from the model curve. In contrast, the four extra deep curves are clearly distinguishable from the model. Near the oil/water contact, all four extra deep apparent resistivity responses are much higher than the model resistivity. This is a polarization effect. In other words, the high resistivities in this zone are a distributed horn effect. The shorter normal propagation resistivity curves evaluate this model as a smooth curve, but the much longer extra deep tool sees a relatively sharp boundary at its scale. The gray curve that does not follow the resistivity curves is the signal strength of the azimuthal tool. This curve is plotted on the same log scale as the resistivity curves in this computer simulation, but in the field logs it will be plotted on a linear scale in a lower track. In a simple two-layer case, the peak of this curve would be at the bed boundary. However, in this case the bed boundary is distributed over a wide gradient so the peak occurs in the middle of the gradient. The maximum signal strength occurs 2 meters above the oil/water contact and is about 2000 nanovolts. An abrupt oil/water contact between a 100-ohmm reservoir and a 0.5-ohmm wet zone would have a peak of about 8000 nanovolts and the peak would be exactly at the boundary. The target wellpath is 9.0 meters (true vertical depth) above the oil/water contact and it is shown by a red line. The azimuthal signal strength at this 9.0 meter point is about 78 nanovolts. The minimum signal detectable must exceed the noise level of 10 nanovolts. The directional indicator for the azimuthal measurement (not plotted here) would be pointing straight down near the oil/water contact showing a conductive zone below the tool. However, at about 1783 meters there is a zero in the signal strength data which is the point where the directional indicator would switch to pointing up. Above the zero crossing the shale above the wellpath more strongly affects the response than the resistivity gradient and water below the wellpath. The point where the azimuthal signal strength is zero and the signal direction changes is often called the electrical midpoint. The electrical midpoint is an important feature any time a resistive zone is bounded by two conductive zones. If the wellpath is maintained at 9 meters above the oil/water contact and only the model resistivity gradient affects the measurements, then the measurements from the tools should be as shown in Table 1:

Table 1: Synthetic Tool measurements 9 meters above oil/water contact, from Figure 3.

2 MHz phase difference 20 ohmmeters

400 kHz attenuation 19 ohmmeters

50 kHz phase difference 43 ohmmeters

50 kHz attenuation 128 ohmmeters

20 kHz phase difference 56 ohmmeters

20 kHz attenuation Off Scale

Azimuthal signal strength 78 nanovolts The dots on the curves in Fig. 3 indicate these values at the 9 meter point. However, other conductive objects unrelated to

this gradient will have an impact on the instrument responses. These are generally shales. In some cases this will be confirmed when the bit drills through a shale that could not be avoided. Our objective is to use the three tools (extra deep resistivity, axial propagation resistivity, and azimuthal resistivity) to define the environment and choose a course of action that will yield the wellpath to optimize production from the reservoir. Determining what fraction of the conductivity response is caused by the resistivity gradient and what fraction is due to other sources is one of the challenges of drilling these wells. To improve the azimuthal data, we try to remove the effect of the gradient. Our strategy is to use the conventional axial propagation resistivity to determine the correct point on the gradient curve. We then subtract the signal strength at the point. For example, at the 9 meter point in Fig. 3 axial propagation resistivity values of 20 ohmmeters for 2 MHz phase difference and 19 ohmmeters for 400 kHz attenuation leads us to estimate the azimuthal signal strength at 78 nanovolts. This value is then subtracted from the measured azimuthal signal strength.

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Fig. 3: Model for the Grane resistivity gradient showing simulated extra deep, axial, and azimuthal propagation resistivity measurements. The target depth is 9.0 m above the oil/water contact. Depth scale is in true vertical depth. Definitions of the abbreviations can be found in the Nomenclature section at the end of the article.

Horizontal Well Data Two horizontal wells were drilled in the reservoir and there were several interesting features in each well. The field data shown in Fig. 4 includes data from all three tools. The conventional propagation resistivity tool has four data curves plotted: Ra2ML (long-spaced 2 MHz attenuation resistivity), Rp2ML (long-spaced 2 MHz phase difference), Ra4kL (400 kHz long-spaced attenuation), and Rp4kL (400 kHz long-spaced phase difference). Only 400 kHz attenuation and 2 MHz phase difference responses are used in the interpretation. Four curves are also plotted for the extra deep tool: Ra50k (50 kHz attenuation), Rp50k (50 kHz phase difference), Ra20k (20 kHz attenuation), and Rp20k (20 kHz phase difference). The lower track contains two curves for the azimuthal resistivity: the signal strength in nanovolts and the bin# which indicates the direction of the maximum signal strength. The signal is divided into 16 bins (from 0 to 15) and the bin# with the maximum signal strength is transmitted to the surface in real time. The middle of the bin# scale (bin#=7 and 8) indicates that the azimuthal signal is coming from directly below the well while the top and bottom (0 and 15) indicate a signal above the well. Bins 8-15 are to the left of the wellpath. The scale on the signal strength (0 to 400 on this figure) varies greatly since data over several orders of magnitude are displayed on a linear scale. A gamma ray curve (in API units) is included in the lower track for reference. At the left of the plot, the tool is drilling out of the well casing. At 2680 meters in Fig. 4, the 2 MHz phase difference is approximately the expected value of 20 ohmm. The 400 kHz attenuation is about 30 ohmm, which is higher than expected but not unreasonable. However, all four of the extra deep resistivity measurements are generally less than the expected values listed in Table 1. This indicates that the extra deep measurements are detecting conductivity in addition to the expected resistivity gradient and the water zone below it. This excess conductivity is probably the result of isolated shale bodies in the reservoir, which are common. The deepest measurement can sense conductivity 30 meters away (in very resistive conditions) so there is a huge volume that is being sensed by the instrument. The azimuthal resistivity tool response is about 120 nanovolts, which is more than the expected 78 nanovolts, so it may also be detecting additional conductivity. The bin# is in the center of the scale which indicates conductivity below the tool. However, in a zone around

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2640 meters the bin# abruptly shifts to the top (bin 15) indicating conductivity above the tool. This is probably a shale body in the reservoir. The small response of the extra deep tools indicates that this is not the roof of the reservoir. A distance-to-bed calculation based on a simple two layer model was made at the peak of the azimuthal signal strength curve and the result was a distance of 1.8 meters. A simple inversion starts with the azimuthal signal strength and the two real-time axial propagation resistivity measurements and produces a distance-to-bed along with the resistivity of the formation. However, the signal strength data in Fig. 4 is affected by the resistivity gradient which will tend to lessen the peak values. The data in Fig. 5 is the result after an adjustment for this effect has been applied. The abrupt transition at the edges of the peak look odd, but this is realistic. The adjustment decreases the signal strength when the conductivity is below the tool and increases it when the detected conductivity is above the tool. The combination of the gradient below the tool and the shale above it compete with each other resulting in lower azimuthal signal strength in the peak in Fig. 4. The adjustment made in Fig. 5 is an attempt to estimate what the effect of the shale alone would be. In addition, a zero crossing of the signal strength is expected in a three layer model when the influence of the top zone and the influence of the bottom zone are equal (the gradient is assumed to be more or less equivalent to a layer). This is called an electrical midpoint, and this zero crossing is observed in the synthetic data of Fig. 3 (at 1783 meters). A calculation of the distance-to-bed with this adjusted data shows that the bed is a little closer, about 1.5 meters away.

Fig. 4: Horizontal well section where a shale zone has been detected at 2640 m. Bin# (0 to 15) shows the direction of the azimuthal signal while APRnv is the signal strength in nanovolts. Bin# 0 and 15 are at the top of the borehole, #7 and #8 are at the bottom. The gamma ray is in API units.

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Fig. 5: The data in Fig. 4 after the effect of the gradient has been removed.

Another log section is shown in Fig. 6. In this case, the gamma ray shows that the wellpath penetrates a small shale body.

The resistivity measurements show a combination of conductive response and horn response, which is consistent with entry into a conductive body at a fairly high angle (that is, the angle between the layer boundary and the wellpath is close to 90 degrees). The azimuthal gamma ray also showed that the entry was at a high angle.

The azimuthal signal strength (note that the scale is now more than an order of magnitude higher than Fig. 5) shows two peaks, one entering the shale and one leaving. The bin# is essentially the same throughout (15). This means that the drillstring entered the bottom of the shale and then exited the bottom of the shale back into the reservoir. A conductive zone above and resistive zone below would give the same direction, which agrees with the constant bin#. If the wellpath had gone through the bottom of a layer and out the top back into the sand, the signal strength would have gone to 0.0 at the electrical midpoint and the bin# would have changed. However, all of this analysis is somewhat suspect because one-dimensional layer cake concepts and models are being used to describe a geology that is clearly not one-dimensional. Nonetheless, it seems reasonable to conclude that the bit drilled through a shale body that was above the wellpath before and after it was encountered. Adjusting the data in this case would not change this interpretation because the result would be an 80 nanovolt correction to a signal response of thousands of nanovolts.

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Fig. 6: Drilling through a small injected shale body. One azimuthal peak entering the shale and one leaving.

Fig. 7 shows data further along the wellpath. After exiting a shale interval at 3788 meters measured depth, the wellpath

continues horizontally into 24 meters of Heimdal sandstone interval with a high water saturation. This sandstone section has a conventional shallow axial resistivity of approximately 1 ohmmeter and a significantly reduced extra deep resistivity. The shale section is marked both by increased gamma and anisotropy. The distinctive separation of the resistivity values of the conventional propagation resistivity tool is a clear indication of anisotropy in the shale (Meyer, 2000). The azimuthal measurements do not respond to anisotropy if the tool is horizontal relative to the anisotropy. From 3778 meters measured depth to 3812 meters the gradually increasing resistivity indicates a gradual reduction in water saturation while drilling more or less horizontally. The four extra deep resistivity curves show an increasing resistivity throughout this sandstone interval. The conventional axial propagation resistivity measurements show a rapid increase as the tool approaches the hydrocarbon bearing zone at 3800 meters. The azimuthal signal strength increases rapidly in this same zone reaching a peak of about 2500 nanovolts at 3801 meters. The peak maximum for a boundary between a 1-ohmmeter wet zone and a 20-ohmm reservoir should be about 6000 nanovolts. The lesser peak attained in Fig. 7 indicates that this is not a sharp boundary but a relatively gradual transition in water saturation. This is hardly surprising since this reservoir is well known for gradual transitions in water saturation. Once the drill string is in the resistive zone, the bin# shows that the conductive wet zone is below the wellpath. As the wellpath goes deeper in measured depth (but still horizontal) the resistivity decreases very gradually as the water saturation increases. The peak in azimuthal signal strength is very broad and reaches a maximum of about 3000 nanovolts. The conductive zone is still shown to be below the wellpath. At 3860 meters the drill string enters a shale. Like the shale on the left edge of Fig. 7, this shale is marked by both increased gamma and anisotropy.

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Fig. 7: Horizontal drilling as water saturation decreases due to water intrusion in the reservoir.

Data from the second horizontal well is shown in Fig. 8. The wellpath approaches a shale body at 2632 meters measured

depth. All of the resistivity curves react. The extra deep curves all show a horn response while the conventional propagation resistivity measurements all show a conductive bed response. Again, this is just a matter of the different scales of the instruments. The shallowest extra deep response (the 50kHz phase difference) seems to split the difference by being almost unresponsive through this zone. The signal strength of the azimuthal measurement peaks at about 320 nanovolts, which would correspond to a distance of approximately 1.6 meters. The shale body is clearly below the wellpath, but when the influence of the shale body clearly exceeds the influence of the gradient, the bin# shifts two bins to the left. This indicates that the shale body is below and somewhat to the left of the wellpath. The steady gamma response shows that the wellpath did not penetrate the shale.

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Fig. 8: A shale body detected below and to the left of the wellpath.

The data in Fig. 9 is similar to that in Fig. 8, except that the shale body is above the wellpath instead of below and to the

left. The azimuthal signal strength is also higher—approximately 800 as compared to 320 nanovolts in Fig. 8. In this case, the extra deep data show lower resistivity than other places in the reservoir indicating that the shale is detected long before it is seen in the azimuthal data. The extra deep data at 2660 meters is consistent with a distance-to-bed of 7 meters, which is too distant for any of the other tools. The extra deep resistivities continue to decrease until the shallower measurements also begin to detect the shale. At that point, the extra deep measurements begin to show a horn response. Just before the azimuthal signal strength begins to show its peak, there is a small dip below the steady level caused by the gradient. This is the electrical midpoint between the gradient below and the shale above that was referred to earlier. There is effectively a sign change between the point where the azimuthal signal points down to where it points up and there should be a zero value (or close to it) somewhere in between. The change in bin# from bottom of the hole to top of the hole is equivalent to changing sign in the azimuthal signal strength measurement. In other words, the signal strength stays positive but its direction reverses.

The same stretch of data is plotted in Fig. 10, except the gradient signal has been subtracted from the observed data. Because the gradient signal is in the opposite direction as the shale signal, this subtraction has the effect of increasing the peak signal. However, since the shale response dominates near the peak, this has a very small effect. The distance-to-bed at the peak is almost exactly 1.0 meter in either case. However, the subtraction does improve the interpretation in the area where the gradient is the dominant effect (for example, at 2660 meters). The distance-to-bed for the uncorrected data (Fig. 9) is 2.2 meters while the distance for the corrected data is about 3.2 meters. The true distance is larger so neither estimate is very accurate. However, adjustment does improve the interpretation and a more accurate method for calculating the gradient might be developed to improve on these results.

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Fig. 9: A shale body above the wellpath.

Fig. 10: The gradient value has been removed from the data of Fig. 9.

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Fig. 11: Shale body below the wellpath with gradient removed.

Fig. 11 shows a much smaller peak in azimuthal signal strength. The interesting thing about the data in Fig. 11 is that the

deeper part (measured depth) shows extra deep resistivity values very close to the model in Fig. 3. The observed responses are very close to the results that are predicted for the anticipated gradient 9.0 meters above the oil/water contact. In other words, these four extra deep measurements do not seem to be detecting much in the way of shale in the reservoir. Therefore, the shale detected by the shallower measurement at 3217 meters must be of limited extent. The bin# does not vary indicating that the shale is directly below the wellpath; modeling indicates that it is about 2.3 meters below the instrument. The limited value of the one-dimensional concepts and models is clearly shown here. If this peak actually represented a conductive layer, there would be a major impact on the extra deep measurements. However, even the shallowest of the extra deep measurements is unaffected.

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Fig. 12: Drilling into the base of the reservoir.

Fig. 12 displays another case where the wellpath goes into and out of a shale body. At 3460 meters, extra deep resistivity

modeling indicates a distance of 5 to 6 meters to a conductive volume below the wellpath. At approximately 3465 meters, the azimuthal resistivity and the axial resistivity begin to detect the shale approaching the wellpath. At 3471 meters, the azimuthal gamma ray showed the shale cutting the wellpath from below. At 3476 meters, the shale was exited at a high angle as indicated by the azimuthal gamma ray and followed by a dirty interval. The shale encountered here may possibly be the base reservoir showing an erosive or deformed contact, which may explain the dirty interval. This is supported by the bin# which shows the conductor below and a little to the right of the wellpath over the interval. This means that the shale approached from below (the wellpath is still horizontal), and the bit both entered and exited the top of the shale.

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Fig. 13: Drilling through a shale with local water saturation variation.

Fig. 13 shows an interval with both shale and variations in water saturation. From 3765 to 3786 meters, the azimuthal

signal strength increases indicating the approach of a conductive body from below. The conventional propagation resistivity in the same interval shows a significant decrease to a resistivity of approximately 1 ohmm before cutting the shale body at 3788 meters. The azimuthal and conventional propagation resistivity are reacting to a local increase in the water saturation of the Heimdal sand towards the flank of the shale, possibly a local change in the oil/water contact due to the gas cap effect described in the introduction. After exiting the shale at 3803 meters the azimuthal resistivity measurement detects conductivity below the wellpath until approximately 3820 meters. The separation of the conventional apparent resistivity curves again demonstrates that this shale is anisotropic. The wellpath penetrated the top of the shale and exited through the same side back into the sand. Inside the shale the directional indicator often shows conductivity above the wellpath. However, this is just sensing variations in the conductivity of shale, not the resistive reservoir. When the azimuthal tool begins to respond to the resistive sandstone at 3800 meters, the bin# goes back to showing a conductor below the wellpath which is equivalent to a resistive zone above it.

Conclusions A combination of three resistivity tools has been used to help geosteer in a reservoir: an extra deep tool, a conventional propagation resistivity tool, and a new azimuthal resistivity tool. The reservoir features a gradient in water saturation that results in a gradual change from about 300 ohmmeters at the top of the reservoir to 0.5 ohmm below the oil/water contact. The optimal wellpath position for draining the reservoir is 9.0 meters above the oil/water contact. The extra deep tool is needed to help define the large-scale resistivity structure from this optimal wellpath. The shallower measurements were used to analyze the resistivity variations much closer to the borehole. In particular, the azimuthal measurement was able to determine directions to conductive bodies. A conductor above the wellpath obviously requires different corrective action than one below, though the angle of incidence was often so high that the shale body could not be avoided. When the contact was below the wellpath then the combined analysis of the measurements of all three resistivity tools was needed to separate an extensive shale rising up to the wellpath from just a smaller shale body in the reservoir.

In some cases, the resistivity measurements of the propagation resistivity tool were used to estimate the response of the azimuthal tool to the resistivity gradient that characterizes this field. Subtracting the gradient signal from the observed azimuthal signal strength gives a more accurate estimate of the distance to a conductive body in the reservoir. The result is a better interpretation of conductive anomalies on and near the wellpath.

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Nomenclature Traditional Propagation Resistivity Data Ra2ML =Attenuation Resistivity for the 2 MHz long-spaced array Rp2ML = Phase Difference Resistivity for the 2 MHz long-spaced array Ra4kL = Attenuation Resistivity for the 400 kHz long-spaced array Rp4kL = Phase Difference Resistivity for the 400 kHz long-spaced array Extra Deep Propagation Resistivity Data Ra20k = Attenuation Resistivity for the 20 kHz extra deep array Rp20k = Phase Difference Resistivity for the 20 kHz extra deep array Ra50k = Attenuation Resistivity for the 50 kHz extra deep array Rp50k = Phase Difference Resistivity for the 50 kHz extra deep array Azimuthal Resistivity APRnv =Azimuthal signal strength in nanovolts Bin# =Direction of the azimuthal signal from 0 to 15 (7and 8 are down, 0 and 15 up)

Acknowledgements We would like to thank the Grane owners StatoilHydro, Petero,ConocoPhillips and ExxonMobil for permission to publish this paper. References Chemali, R., Helgesen, T., Meyer, H., Peveto, C., Poppitt, A., Randall, R., Signorelli, J., Wang, T., “Navigating and Imaging in Complex

Geology With Azimuthal Propagation Resistivity While Drilling”, 2006 SPE ATCE, 24-27 September 2006, San Antonio, Texas. Helgesen, T., Fulda, C., Meyer, H., Thorsen, A, Baule, A., “Navigating with an Extra Deep Resistivity LWD Service”, 2005a SPWLA

Symposium, June 2005, New Orleans, Louisiana. Helgesen, T., Meyer, H., Thorsen, A., Baule, A., Fulda, C., Ronning, K., Iversen, M., ”Accurate Wellbore Placement using a Novel Extra

Deep Resistivity Service”, 2005b SPE Conference June 2005, Madrid, Spain. Helgesen, T., Thorsen, A., Kroken, A., Ronning, K., Harsas, A., ”Real Time J-Function and Optimal Well placement Utilizing Mobility

and Resistivity data”, 2006 SPWLA Symposium, June 2006, Veracruz, Mexico. Meyer, H., “A New Prototype Slimhole Multiple Propagation Resistivity Tool”, 1994 SPWLA Symposium, June 1994, Tulsa, Oklahoma. Meyer, H., “Analysis of Environmental Corrections for Propagation Resistivity Tools”, 2000 SPWLA Symposium, June 2000, Dallas,

Texas.