چكيده به لاتين
Water production is one of the major problems in the oil industry. Nowadays, the highest amount of waste products in the oil and gas industry is dedicated to water production. Based on Schlumberger’s report, about 75 percent of reservoir production in the world, which is 220 MSTB, is dedicated to water production that 11 million dollars is spent on treating it.
Three workover and production methods have been investigated in this survey, which are recompletion, down-hole water separation, and down-hole water sink. At first, a comparison between conventional production and related method has been implemented separately, then in order to select a proper simulation model, dependency of block numbers in both vertical and radial directions has been investigated. Further, production operational designs have been optimized, then anisotropy effect analysis has been got into the consideration, and finally, in order to verify optimal production design, a comparison between the optimal and non-optimal design of production method has been implemented.
A comparison between all three production methods and conventional one has been done, which has resulted that in all three methods, the objective function has been improved compared with the conventional method. Dependency investigation of block numbers in recompletion method in vertical and radial directions has been resulted that there is not any sensible sensitivity regarding the number of blocks in both directions. By increasing the time and the plugging length of recompletion, net present value has declined and hiked respectively. The final optimization results of recompletion method verify the sensitivity analysis results, which means that optimal recompletion should be done in earlier production time with the least length of recompletion. Although oil production rate is not fluctuated by increasing the anisotropy ratio in recompletion model, water production is increased until 11th production year then it begins to fall. Regarding comparing of optimal and non-optimal recompletion method, it has resulted that optimal recompletion method increases the oil production rate and lowers the water production rate from oil well more sensible than non-optimal recompletion method.
In down-hole water sink method, it has been concluded by dependency investigation of block numbers in both radial and vertical directions that although final production results by increasing the number of blocks in vertical direction is not changed significantly, it has more sensible trend in radial direction, why two models with different block numbers have been chosen as fine model and coarse model. By increasing the water drainage rate from the aquifer, NPV has been hiked, then decreased, and finally, it remains constant. Also, by increasing the length of oil and water completion and also the distance between water drainage completion and WOC, NPV has been decreased. Even though Simultaneous optimization final results have been confirmed by final sensitivity analysis results, Sequential results in DWS have some difference with simultaneous one. Due to the fact that optimization results which have been stemmed by fin model are more realistic than coarse model but the runtime of fine model is much more than coarse model, fine model optimization has been performed by considering the coarse model final results as initial chromosomes of fine model, which has been resulted that final results relating to both models are roughly equal to each other. By increasing the anisotropy ratio, the tendency of vertical water movement is increased comparing with oil movement to pay zone; as a result, water production has been hiked and oil production has been decreased, due to the wettability of reservoir rock, which is oil wet. Comparing the optimal down-hole water sink and non-optimal method has resulted that NPV is much more in optimal method comparing with non-optimal one.
Sensitivity analysis of block numbers in both radial and vertical directions for down-hole water loop method has resulted that nevertheless in vertical direction no sensitivity has been detected, in radial direction it is much more sensible, which has been resulted that two models with different block numbers have been chosen as fine and coarse model in down-hole water loop method. Increasing the water drainage rate from aquifer hikes NPV to the certain value, for the rates higher than this certain amount, NPV has remained constant. By increasing the length of oil completion and the distance between WOC and water drainage completion, NPV has the decreasing trend, and also by enlarging the D/I spacing, NPV is increased until certain value, and for amounts higher than this amount, NPV has remained constant. Also, by increasing the water drainage completion length, NPV trend is shaped like the bell but there is not any significant change in value. Like DWS optimization results, simultaneous results in DWL have been confirmed by sensitivity analysis of this method, by the way, sequential results are not qualified like simultaneous method. Due to the fact that optimization results which have been stemmed by fin model are more realistic than coarse model but the runtime of fine model is much more than coarse model, fine model optimization has been performed by considering the coarse model final results as initial chromosomes of fine model, which has been resulted that final results relating to both models are exactly equal to each other. By increasing the anisotropy ratio, the tendency of vertical water movement is increased compared with oil movement to pay zone; as a result, water production has been hiked and oil production has been decreased, due to the wettability of reservoir rock, which is oil wet. Comparing the optimal down-hole water loop and non-optimal method has resulted that NPV is much more in optimal method compared with non-optimal one.
