Sang, Guangsen (Daqing Oil Field Co. Ltd.) | Jiang, Zhenhai (Daqing Oil Field Co. Ltd.) | Zhang, Qingjie (Daqing Oil Field Co. Ltd.) | Wei, Jianguang (Northeast Petroleum U.) | Zhang, Tianjun (Daqing Oil Field Co. Ltd.)
In long horizontal wells, early water or gas may breakthrough into the wellbore due to imbalanced production profile caused by heel-toe effect, reservoir heterogeneity or fracture existing. Once coning occurs, oil production may be severely decreased due to limited flow contribution from the other regions. Passive inflow control devices (ICD) are installed to maintain the flow across production zones uniformly by creating an additional ICD pressure differential which cancels out the imbalanced production profile. This will lower startup production, however, unwanted fluids from breaking through are significant delayed, and total oil production is maximized. Unfortunately, once water/gas does break through, they will take over the well, significantly reducing oil production.
In this paper, a novel autonomous inflow control device (AICD) design is proposed based on the combination of nozzle-based ICD and water swelling rubber (WSR). The WSR installed in the nozzle swells once water breakthrough occurs, and the swell increment will be adjusted automatically according to water content, thus changing the minimum flow area and flow resistance rating (FRR) of the device. This autonomous function enables the well to produce oil while restrict water. To highlight the excellent performance of the AICD design, three other designs (nozzle-based, helical channel, and tube-type) with a same FRR of 0.8 were compared, with fluid property sensitivities, structural parameter and arrangement optimization researched. The results show that the device has a good performance for both oil producing and water restricting, which enables the well to continue producing oil for a longer time, and maximizing the total production.
Zeng, Quanshu (China University of Petroleum-Beijing) | Wang, Zhiming (China University of Petroleum-Beijing) | Yang, Gang (China University of Petroleum-Beijing) | Wei, Jianguang (Northeast Petroleum University)
In long horizontal wells, production rate is typically higher at the heel than that at the toe. The resulting imbalanced production profile may cause early water or gas breakthrough into the wellbore. Once coning occurs, well production may be severely decreased due to limited flow contribution from the toe. To eliminate this imbalance, inflow control devices (ICDs) are placed in each screen joint to balance the production inflow profile across the entire lateral length and to compensate for permeability variations.
Currently, there are three different passive ICD designs in the industry: nozzle-based, helical channel, and tube-type. They use restriction mechanism (nozzle-based), friction mechanism (helical channel) or cooperating the two (tube-type) to achieve a uniform inflow profile. However, the reality is that none of these ICDs alone meets the ideal requirements of an ICD designed for the life of the well: high resistance to both plugging and erosion, high viscosity insensitivity, and high density sensitivity. Therefore, the selection and optimization of ICDs for a specific reservoir requires for further study. In this paper, three computational fluid dynamic based, numerical models of these ICDs with same flow resistance rating (FRR) were developed to characterize the flow performance. The results show that the throttle pressure drop depends on fluid properties, and geometries of each ICD. The weight of each factor that affects pressure drop was determined by maximizing deviations combining with analytic hierarchy process, and subsequently optimal ICD under specific reservoir condition was selected with the help of fuzzy comprehensive evaluation, thereby an ICD selection diagram was built. For a specific reservoir, we will have the selected ICD with best pressure drop composition by optimizing its structural parameter, which has best corrosion resistance and least viscosity sensitivity.
Xin, Shuzhen (Daqing Oilfield Co. Ltd.) | Zhang, Qingjie (Daqing Oilfield Co. Ltd.) | Wei, Jianguang (China University of Petroleum, Beijing) | Chen, Ying (Daqing Oilfield Co. Ltd.) | Wang, Rongjiu (Daqing Oilfield Co. Ltd.) | Wang, Jingbo (China University of Petroleum) | Wang, Xiaoqiu
Aiming at the low viscosity of polymer solution, which is compounded with fresh water but diluted with produced water, and at the problems concerning oil displacement efficiency, an onsite test on polymer solution with viscosity stabilizer (PSVS) is carried out. As a result, it has great and guiding significance to the application and popularization of viscosity stabilizer by studying the performance of polymer solution with viscosity stabilizer and its influence on oil displacement efficiency. In this paper, aiming at two different kinds of polymer solutions among which one is compounded with fresh water but diluted with fresh produced water and the other with aerated produced water, two laboratory evaluative tests concerning viscosity stabilization, anti-shear stability, fluidity, and absorbability of polymer solution as well as its oil displacement efficiency are done. The results of onsite application of PSVS are traced and analyzed.
The viscosity stabilization of the polymer solution adding with viscosity stabilizer becomes much better than that of the normal polymer solution. The resistance and the residual resistance factors, the static oil sand adsorption rate and the dynamic core adsorption rate of the solution are all increased markedly. The working viscosity and oil displacement efficiency are improved markedly as well. In comparison with the polymer solution diluted with fresh produced water, the polymer solution diluted with aerated produced water is much better in terms of viscosity stabilization. Comparing with the normal polymer solution with viscosity stabilizer before sheared, the polymer solution which is sheared before adding with viscosity stabilizer performs obviously better in terms of viscosity stability. In contrast to the adjacent block injected with normal polymer solution, the block under onsite flooding test with injection of PSVS features that the average injection pressure increases slightly but keeps steady, the recovery speed of the average monthly water cut of production wells slows down, the thickness of the absorptive layers increases, and the periodic recovery rate improves as well.
Wei, Jianguang (China University of Petroleum, Beijing) | Tao, Jianwen (Daqing Oilfield Co. Ltd.) | Xin, Shuzhen (Daqing Oilfield Co. Ltd.) | Zhang, Qingjie (Daqing Oilfield Co. Ltd.) | Zhang, XIn (Daqing Oilfield Co. Ltd.) | Wang, Xiaoqiu (China University of Petroleum)
In the process of oil displacement of ASP (Alkali/Surfactant/Polymer) flooding , when Alkali interacts with the fluid and minerals of the reservoir, the alkali is subject to be consumed. The consumption regularity is the key factor affecting ASP ingredient, injection plan, scaling regularity for production wells and oil displacement effectiveness. Therefore to study the alkali consumption is of great significance in guiding ASP ingredient, injection project design, and the analysis for oil displacement mechanism. In this paper, aiming at the main components of minerals in the reservoir in Daqing Oilfield, the laboratory study on static alkali consumption for five kinds of minerals (kaolinite, grundite, chlorite, feldspar and quartz) in ASP system and single component NaOH solution are done respectively. The alkali consumption regularities for five kinds of minerals in ASP and single component NaOH solution are concluded.
The research indicates that the amount of alkali consumption for kaolinite, grundite, chlorite, feldspar and quartz is changing from larger to less accordingly, but is mainly caused by clay minerals; the average alkali consumption is 18.3% higher than that by matrix minerals. In single component NaOH solution, the alkali consumption styles of clay minerals and the matrix minerals take the chemical reaction as the lead, and the physical adsorption as the second. In ASP system solution, the alkali consumption style of clay minerals, takes the physical adsorption as the lead, and of matrix minerals takes the chemical reaction as the lead. In ASP solution, compared with single component solution, polymer and surfactant have the functions of restraint to alkali consumption in minerals of the reservoir, and the amount of alkali consumption decreases evidently.
Because of heterogeneity in permeability along horizontal wellbores, early water breakthrough and rapid water-cut increase are always observed in high-permeability completion intervals when a uniform perforating scheme, as a common practice, is applied throughout the wellbore. Optimization on perforation parameters along horizontal intervals helps homogenize the inflow-velocity profile and thus is critically important for enhanced oil recovery. This paper derives a coupled reservoir/wellbore flow model that is based on inflow-velocity-control theory. Genetic algorithms are applied to solve the model because they excel in obtaining the global optimal on discrete functions. The optimized perforating strategy applies a low perforation density in high-permeability intervals and high perforation density in low-permeability intervals. As a result, the inflow-velocity profile is homogenized and idealized.
The recovery efficiency by polymer flooding is 10% higher than that of water flooding for main reservoirs in Daqing Oil Field, and yearly oil production rate by polymer injection has continuously reached over 10 million tons for 8 years . However, to further enhance oil recovery, it is very important to know how many oil remained in the reservoirs after polymer injection as well as its distribution. The paper took use of logging data of 200 new drilling wells to make macro analysis on remaining oil distribution after polymer injection, and based on the data of coring wells, collected from the same well group in Western Fault of B1 Region, before and after polymer flooding, respectively, core membrane fluorescence technology was used to conduct the analysis on microscopic remaining oil distribution.
The macro analysis results indicate that swept thickness of the reservoir increased 21.4% from 68.6% of water flooding to 90% of polymer flooding, and oil saturation reduced 11.9% from 52.8% to 40.9%, and displacement efficiency has went up 7.6 percentages. The residual oil distribution after polymer flooding is scattered in horizontal direction, while it is interleaved in vertical direction. Following polymer flooding, 10.6% unswept thickness is mainly distributed in thick oil layers, and most of remaining oil within thick oil layers lies in the interlayers and at the top of thick oil layers, which its effective thickness is close to 80%. From the macro point, remaining oil is mainly located in distributary line or some places where injection and production relation is imperfect or the phase is changed, and oil saturation located in distributary line is 4.4 percentages higher than that along mainstream line. The micro analysis results show that the behavior of remain oil distribution is similar to water flooding, which is mainly controlled by capillary force.