Summary of FOPT increases versus changes in well length
4.2 Field model tests on multiple realizations
4.2.1 Solution tests on multiple realizations: 1200 day production time frame
In this section we present results from each of the well placement solutions tested on the set of 11 realizations using the 1200 day production time frame. Results corresponding to the 5174 day production horizon are discussed in Section 4.2.2.
Table 4.7: Mean FOPT increase (ΔFOPT) and well mean WOPT increases (ΔWOPT) for all solutions tested over the multiple realization set. Each of the increases has a corresponding stan-dard deviation from the mean (σ). Production data is obtained from Eclipse simulations running original base case production strategy (xSc) over a1200 day production horizon.
Solution ECLIPSE1200
x∗p, xSc
ΔFOPT ΔWOPT
WL.-A WL.-B WL.-C WL.-D
[%] [σ] [%] [σ] [%] [σ] [%] [σ] [%] [σ]
BASECASE 0.0 0.119 0.0 0.215 0.0 0.284 0.0 0.298 0.0 0.255 FXD1M1 1.9 0.183 -0.3 0.222 19.2 0.374 0.4 0.338 -3.3 0.164 FXD2OPT 1.9 0.226 -0.2 0.264 10.6 0.466 -11.5 0.233 16.9 0.343 FXD2OPT2 0.4 0.214 -2.2 0.247 5.2 0.437 -15.0 0.304 20.7 0.349 FXD2CUT 1.7 0.190 -4.3 0.242 -0.8 0.428 -2.9 0.250 16.1 0.223 JNT2M1 6.7 0.215 5.3 0.172 32.2 0.449 -3.2 0.233 6.8 0.313 JNT1M1 6.3 0.213 4.2 0.171 31.1 0.442 -3.0 0.231 6.6 0.315 JNT2OPT 2.9 0.208 -2.4 0.236 15.7 0.337 -9.2 0.239 17.7 0.333 JNT2OPT2 0.9 0.222 -1.6 0.246 5.0 0.443 -8.8 0.254 14.2 0.339 JNT2CUT 0.1 0.215 -2.3 0.237 -0.4 0.430 -7.7 0.235 13.2 0.354
Mean FOPT increase (ΔFOPT) and standard deviation data (σ) corresponding to each solution tested on the multiple realization set are given in Table 4.7. Well mean WOPT increases (ΔWOPT) with associated standard deviations are also given. As expected, we see that for each solution in this time frame, the mean FOPT increase over all realizations is significantly lower than the FOPT increase using only the single base case realization.
(It should be noted that, when using the base case well configuration, the FOPT curve corresponding to the original base case model realization clearly outperforms the FOPT curves corresponding to all the other realizations. I.e., when using base case wells on the original base case model realization we obtain the FOPT profile corresponding to the dashed line, upper–most gray curve in Figure 4.25. Also we see that for each solution well configuration tested over the set of multiple realizations, the best–performing FOPT curve is the one obtained when using the solution wells on the original base case model realization. This observation holds for all the multiple realization field production curves presented in this work, but not for the cumulative oil production profiles of the individual wells.)
Comparing the results in Table 4.7 with their counterpart single realization results shown in Table 4.5 (page 143), we see that the two best solutions from the single realiza-tion data, solurealiza-tions JNT2M1 and JNT2OPT, decrease from 25.5% and 24.9% to 6.7% and 2.9%, respectively, when tested over multiple realizations (since JNT1M1 is a slight vari-ation of JNT2M1, in this section the discussion of the JNT2M1 solution also applies to the JNT1M1 solution). The other solutions have steeper decreases, and are all below 2%
for the multiple realizations case. Standard deviations corresponding to the mean FOPT of each solution are on average 1.8 times higher than the standard deviation for the base case. (Standard deviation tells us something about the spread of the data that make up the mean. In this context, it provides us with a measure of how robust a solution is with respect to the uncertainty represented by the multiple realization set.)
We notice the standard deviations corresponding to the solution A wells do not differ much from the standard deviation for the base case A well. Also, the standard deviations for all the solution C wells (except for the FXDM1 C well) are lower than the standard deviation for the base case C well. However, the standard deviations for the solution B and D wells show greater variation and are, on average, 1.5 and 1.2 times higher, than the standard deviations for their corresponding base case wells, respectively.
As discussed in the previous section, high increases in FOPT for several of the solu-tions are due to significant contribusolu-tions from both the B and D wells. This is particularly the case for the JNT2M1 and the JNT2OPT solutions, which as mentioned, are the two solutions that have the highest FOPT increase in both the single and multiple realizations case. From the multiple realization data shown in Table 4.7, we see that the B well in these solutions has lost almost three–quarters of its gain compared to the single realization case (see Table 4.5). The decrease for the B wells in these solutions is due to the fact that in the base case map, these wells are draining an additional culmination to the south–east which may not be as high in other realization maps. Similarly, in the single realization case, the D well in these two solutions more than doubled its total production compared to base case, while in the multiple realization case, the increase in D well oil production for these two solutions is much less than 20%. For the JNT2M1 solution, standard deviations for these wells are close to average, i.e., B and D well standard deviations are 1.6 and 1.2 times higher, respectively, than their counterpart base case wells. For the JNT2OPT solu-tion B well, standard deviasolu-tion is lower than average at 1.2 times higher than base case B well, while D well standard deviation is 1.3 times higher than its base case analog.
Overall, both the JNT2M1 and JNT2OPT solutions show significant decreases when implemented over multiple realizations. In the multiple realization case, the mean well oil
production increases obtained from the B and D wells in the JNT2M1 and JNT2OPT solu-tions are much lower than the analog WOPT increases in the single realization case. How-ever, in both the single and multiple realization case, these wells still drive much of the FOPT increases for these solutions.
In the following we plot the field and well cumulative oil profiles when using the JNT2M1 wells for each realization. For comparison, we also plot the production pro-files obtained when using the base case wells over the same realizations. We choose the JNT2M1 solution because it is the solution with highest mean oil production total in Ta-ble 4.7.
Field and well oil production profiles for JNT2M1 solution
In figures 4.25 and 4.26 we plot the field and well cumulative oil production profiles for the JNT2M1 solution over the 1200 day production time frame. Production profiles corresponding to the solution are plotted as dark red curves, while base case production plots are drawn in gray. Curves representing average FOPT and WOPT production profiles for the solution and base case are plotted as thick red and gray lines, respectively.
0 200 400 600 800 1000 1200
0.00 0.25 0.50 0.75 1.00 1.25 1.50
[days]
FOPT [−]
BASECASE vs JNT2M1
JNT2M1 BASECASE
Figure 4.25: Field oil production totals for multiple realization case using the JNT2M1 so-lution (red) and base case well configuration (gray) over a production time frame of 1200 days. Dashed lines correspond to the original base case realization. Thin lines correspond to FOPT curves for individual realizations, while thick lines represent the average FOPT over all realiza-tions.
Field oil production total plots. Figure 4.25 shows the field oil production total for each model realization running with the JNT2M1 solution. It also shows the field oil production totals for the same realizations when using the base case well configuration. In this figure we see that the mean FOPT curve for the JNT2M1 solution stays above the base case average for the entire 1200 day production time frame. As seen in Table 4.7,
0 200 400 600 800 1000 1200
0 200 400 600 800 1000 1200
0.00
0 200 400 600 800 1000 1200
0.00
0 200 400 600 800 1000 1200
0.00
Figure 4.26: Well oil production totals for multiple realization case using the JNT2M1 solu-tion (red) and base case wells (gray) over a producsolu-tion time frame of1200 days. Dashed lines correspond to the original base case realization. For each well graph, thin lines correspond to WOPT curves for individual realizations, while thick lines represent the average WOPT over all realizations. Upper left and right graphs correspond to wells A and B, while production profiles for wells C and D are shown in the lower left and right graphs, respectively.
after 1200 days of production, the mean FOPT increase from the JNT2M1 solution is 6.7% larger than mean FOPT using the base case wells. For about the first 300 days of production, all FOPT curves for the JNT2M1 solution outperform their corresponding base case FOPT curves. From this point on, at least three solution FOPT curves veer off the general trend of the average FOPT curve. Covering the complete 1200 day period, two FOPT curves from the JNT2M1 solution (including the one corresponding to the base case model realization) greatly outperform their average.
Well oil production total plots. Figure 4.26 presents four separate graphs showing the cumulative oil profiles for each of the JNT2M1 wells over all model realizations. The graphs also show the oil production totals for the corresponding base case wells. In addi-tion, for each of the four graphs, we can compare the mean production from each of the JNT2M1 solution wells to the mean performance of their corresponding base case wells.
Here we focus on comparing the performances for the multiple realization case against the well increases achieved in the single realization case. (Recall that single realization
WOPT plots for all solutions are shown in Figure 4.24, with detailed values given in Ta-ble 4.5.) In the single realization case, we have seen that the A well for the JNT2M1 solution shows no WOPT increase while its C well has a 13% decrease in WOPT com-pared to their respective base case wells. However, in the multiple realization case, we see from the upper left graph in Figure 4.26, that the A well for the JNT2M1 solution has a slight increase in mean WOPT compared to the base case mean, and from the lower left graph we notice that its C well mean WOPT is now only a few percent below its corresponding base case mean. Thus, relatively, the contributions from the A and C wells for this time frame increase in the multiple realization case. At the same time though, as we have noted before, the significant gains in mean total oil production achieved by the B and D wells in the single realization case are comparably much lower in the multiple realization case. Comparing the mean increases in the upper and lower right graphs in Fig-ure 4.26 with the WOPT increases shown in FigFig-ure 4.24, we see how the gains achieved for these wells are significantly reduced once they are tested over the multiple realization set. In the following section we see these gains are harder to retain when solutions are tested over the larger field production horizon.