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Jia, Ying (Petroleum Exploration and Production Research Institute, SINOPEC) | Shi, Yunqing (Petroleum Exploration and Production Research Institute, SINOPEC) | Huang, Lei (Research Institute of Petroleum Exploration and Development, Petrochina) | Yan, Jin (Petroleum Exploration and Production Research Institute, SINOPEC) | Sun, Lei (SouthWest Petroleum University)
The YKL condensate gas reservoir is one of the biggest condensate gas reservoirs in China and has been developed more than 10years. At present, the combination of subdivision layer, production speed optimization and horizontal well drilling has been the key to economically unlocking the vast reserves of the YKL condensate gas. The primary recovery factor, however, remains rather low due to high capillary trapping and water invasion. While primary depletion could result in low gas recovery, CO2 flooding provides a promising option for increasing the recovery factor.
The objective of this work is to verify and evaluate the effect supercritical CO2 on enhancing gas recovery and analyze the feasibility of CO2 enhance gas recovery (CO2 EGR) of condensate gas reservoir.
Firstly, novel phase behavior experimental procedures and phase equilibrium evaluation methodology for gas-condensate phase system mixed with supercritical CO2 with high temperature were presented. A unique phase behavior phenomena was also reported. Then, CO2 floodingmechanism in condensate gas reservoir was analyzed and clarified based on experiments. Finally, a series of numerical simulation work were conducted as an effective and economical means to maximize natural gas recovery with the lowest CO2 breakthrough by varying strategies, including CO2 injection rate, injection composition, andinjection timing. Meanwhile the CO2 storage volumes of different strategies were calculated.
The results show that higher gas recovery factor can be achieved with CO2 injection through appearing interphase between two fluids, maintaining reservoir pressure, driving gas like "cushion" and controlling water invasion. All strategies have moderate to significant effects on gas production. The control of injection and production ratio needs to be balanced between pressure transient and CO2 breakthrough over the producer to obtain the maximum gas production. The varying injection pressure shows a positive effect of enhancing gas production. Numerical simulation indicated that the recovery of gas reservoir was improved by around 10 percent. The total CO2 storage would be around 30-40% HCPV.
The research showed that CO2 flooding presents a technically promising method for recovering the vast condensate gas while extensively reducing greenhouse gas emissions.
Han, Rubing (Research Institute of Petroleum Exploration and Development, Petrochina) | Li, Shunming (Research Institute of Petroleum Exploration and Development, Petrochina) | Song, Benbiao (Research Institute of Petroleum Exploration and Development, Petrochina) | Tian, Changbing (Research Institute of Petroleum Exploration and Development, Petrochina)
The giant H oil field was discovered in 1976 and put into development in 2008. The Mishrif reservoir has half of the geological reserves, and the current development challenges are greater. First, the sedimentary evolution is very complicated (inner ramp, lagoon, shallow sea, et al), the existing facies model is generally derived from rock type interpolation with kriging algorithm, and does not reflect sedimentary understanding, and is quite different from the actual situation displayed by seismic data. Furthermore, the variogram of rock types is also difficult to be accurate, resulting in poor fitting of reservoir simulation. Second, the seismic data quality is generally low, and its correlation with rock types is worse. If it is directly used to constrain rock type interpolation, the accuracy is generally unsatisfactory.
In order to solve these problems, this study first comprehensively studied the core, thin slices, scanning electron microscopy, X-ray diffraction, electron probe and other data for sequence stratigraphy and sedimentary research. Secondly, based on the single well facies interpretation, combined with the inversion data, the dimension, spatial relationship and variogram of each depositional element were studied. Thirdly, the facies model was built using the Sequential Indicator Simulation (SIS) algorithm, and was manually modified zone by zone according to the sequence stratigraphy and sedimentary understanding. Finally, the relationship between depositional elements and rock types was studied, and the probability bodies of different depositional elements with different rock types were obtained. Based on this, the SIS algorithm was used to simulate rock types. Then this could be further used as a constraint to build petrophysical models.
The results showed that the correlation between the depositional elements and the rock type was obviously better than the inversion wave impedance. The artificially modified facies model could better reflect sedimentary appearance, and various static and dynamic data. The rock type model obtained under the constraint of the facies model also bypassed the problem that the seismic data quality was not good enough for direct rock type interpolation.
It was verified that with the new modeling workflow, the preliminary numerical simulation fitting rate reach over 80%. The facies model was then verified with water flooding test in H oil field and had good results. This workflow could provide a good reference for similar oilfields in the Middle East.
Tao, FU (Research Institute of Petroleum Exploration and Development, Petrochina) | Xiaohan, Pei (Research Institute of Petroleum Exploration and Development, Petrochina) | Qinghai, Yang (Research Institute of Petroleum Exploration and Development, Petrochina) | Yili, Hu (National Key Laboratory of Nano/Micro Fabrication Technology, Shanghai Jiaotong University) | Eryang, Ming (Research Institute of Petroleum Exploration and Development, Petrochina) | Siwei, Meng (Research Institute of Petroleum Exploration and Development, Petrochina) | Shouzhi, Huang (Research Institute of Petroleum Exploration and Development, Petrochina)
At present, most of the small-scale equipments used in monitoring underground oil exploration pipelines are powered by disposable or rechargeable batteries. These traditional chemical batteries have been unable to meet the needs of the system due to their large mass and volume, limited energy supply and possible environmental pollution. In addition, the huge depth of the oil wells can lead to a great deal of inconvenience during the replacement of the batteries. To solve these problems, a piezoelectric vibrator based on MEMS is proposed to achieve continuous supply of small downhole equipment in the process of oil/gas development.
In this study, after analyzing and optimizing the structural parameters of the device, a prototype is designed and fabricated through MEMS processing techniques including bulk silicon micro fabrication, bonding, and thinning. The prototype consists of a support layer, a piezoelectric film layer and a tip mass-block. Copper or silicon with appropriate stiffness and suitable for MEMS processing techniques are selected to make the support layer; PMN-PT with superior performance is selected to fabricate the piezoelectric film layer, whose working mode is d31. By running the energy acquisition test, the characteristics of the prototype's output voltage, power, and frequency are studied, as well as the possible requirements for the matching circuit.
The study shows that the test results are in good agreement with the calculated results of the theoretical model. The test results show that when the acceleration is 1.5g, the frequency bandwidth of the proposed prototype is 34.6Hz in air and 50.3Hz in silicon oil, and the output power can reach 35.4μW in air and 4.96μW in silicon oil.
Compared with the current mainstream piezoelectric thin film MEMS devices, this energy harvester based on MEMS technology has the advantages of superior output performance, simple fabrication, high anti-electromagnetic interference reliability, and easy integration with support circuit. This device will provide a new solution for the energy supply of downhole small-scale monitoring equipment.
Carbonate reservoirs are of strong heterogeneity. Their geological features and dynamic behaviors vary significantly for different types of carbonates. Characterizing the distribution of different types of carbonates and proposing different development strategies are critical for a successful development of carbonate reservoirs. This paper focuses on a super-giant carbonate reservoir with OOIP (Original Oil in Place) of more than 20 billion barrels. However, it has been naturally depleted over the past 40 years. Its reservoir pressure is approaching the bubble point pressure. Therefore, it is critical and urgent to propose optimized water flooding plan for this reservoir.
In this paper, the dataset includes seismic data, well logs, production history, dynamic surveillance data, et al. Firstly, three reservoir types are characterized as good, medium and poor reservoirs based on static and dynamic data. Then, the stacking patterns of different reservoir types are concluded and their distributions are determined, which provide us the foundation to propose customized water flooding plan. Finally, the water flooding performances of different stacking patterns are analyzed and full-field development strategies are proposed based on fine-scale geological modeling and numerical simulation.
Results indicate that stacking pattern has intimate relationship with facies map. For example, the distribution of stacking pattern A, in which good reservoir accounts for the majority, is consistent with the distribution of favorable grainstone shore facies, indicating very good reservoir quality that resulted in higher production rate, longer stable production period, and slow decline. In addition, different offtakes, well patterns, pressure maintenance, well types of different reservoir stacking pattern are determined based on the simulation results and distribution of different stacking patterns. The EUR is increased by more than 20% compared with natural depletion.
This paper offers a reference case of grouping different types of reservoirs and proposing customized water flooding plan, which help engineers and geologists to better develop other similar fields.
Xu, Anzhu (Research Institute of Petroleum Exploration and Development, Petrochina) | Mu, Longxin (Research Institute of Petroleum Exploration and Development, Petrochina) | Zhao, Liangdong (Research Institute of Petroleum Exploration and Development, Petrochina) | Wang, Chenggang (Research Institute of Petroleum Exploration and Development, Petrochina) | Zhang, Chengshuo (Research Institute of Petroleum Exploration and Development, Petrochina)
The main factors of influencing the recovery efficiency of gas drive are miscible degree and gas channeling in carbonate reservoirs with double porosity. The components of injection gas significantly influence the miscibility of enriched gas with the same important function of the minimum miscibility pressure, reservoir pressure. High hydrogen sulphide content (H2S) and carbon dioxide (CO2) content in reservoir production, abnormally high reservoir pressure (>70MPa) and specifics of field position (offshore) lead to great challenge for this kind of oil field development. Produced sour gas as an injection fluid without desulphurisation to reduce investment cost and therefore decrease negative environmental impact is proposed a good way to solution the oil filed development problem. Some produced gas samples were analyzed in laboratory. Detailed PVT results on miscibility of reservoir oil and injection gas showed a good correlation of the majority of the parameters, and the established compositional model calculations illustrated that when the content of H2S and CO2 become higher, the injection gas were more easily fully solved in the oil and residual oil saturation could be reduced to the minimum level. Another important aspect solved during the reservoir modeling in this study was definition the changes of minimum injection gas and reservoir fluid miscibility pressure with the variety of the content of the sour gas. During the injection gas combined drive, miscible displacement could take place horizontally or vertically depending on the reservoir configuration. This work illuminated vertical displacement generally occurs in widely spread steeply dipping structures. The efficiency of gas re-injection into the upper part of the reservoir and production of oil from the base for vertical displacement is low due to the flow barrier which limits vertical gas advancement.
Mu, Longxin (Research Institute of Petroleum Exploration and Development, Petrochina) | Zhang, Ming (Research Institute of Petroleum Exploration and Development, Petrochina) | Ren, Bin (Research Institute of Petroleum Exploration and Development, Petrochina) | Xia, Zhaohui (Research Institute of Petroleum Exploration and Development, Petrochina) | Zhang, Xiaoling (Research Institute of Petroleum Exploration and Development, Petrochina) | Zhang, Wenqi (Research Institute of Petroleum Exploration and Development, Petrochina) | Li, Chunlei (Research Institute of Petroleum Exploration and Development, Petrochina) | Zheng, Yabin (Petrochina International Companies in Indonesia)
In the development of conventional oil and gas projects, inter-well sandstone prediction and facies evolution provide benefit by reducing the number of wells drilled, optimizing well location and maximizing the performance of the wells. However, several particularly thorny issues were encountered in our study. Multi-bedded thin sandstone reservoirs were vertically stacked with thin coal seams. The main sedimentary facies of sandstones in areal and vertical directions varied quickly. This paper summarizes one multidisciplinary integration methodology to predict the distribution of inter- well sandstone and sedimentary facies in the South Sumatra Basin in Indonesia.
To overcome the aforementioned disadvantages, this method included the following steps. First, it made use of multidisciplinary knowledge including mineralogy, sedimentology, lithology, geology, petrophysics and geophysics based on cores, well logs, and seismic data of various source data. Second, sequence strata division and correlation were studied with eleven target layers in order to describe this multi-stack reservoir. Then sedimentary facies system including braided channel and braided delta were identified based on reliable data from sedimentary structure of lithology, facies sequence, Formation Micro scanner Image data (FMI), and sedimentary characteristics of core samples such as: rock color, lithological features, mineral composition, and rock sedimentary structure. Fourth, a sandstone identification assessment standard was established to improve the precision of the reservoir prediction. Fifth, logging data and sedimentary facies were used to establish the facies log patterns. Favorable reservoir facies in strata were outlined based on the study of properties of sedimentary facies. Sixth, a four step procedure including seismic data partitioning, seismic attribute analysis, normalized seismic attributes of three compartments and sandstone thickness calculation was used to identify sandstone inter-well distribution. Seventh, multidisciplinary integration was used to understand facies and facies evolution to arrive at favourable facies and properties distribution which could then be used for geomodel building.
This methodology constitutes a systematic and effective way to delineate the distribution of sandstones and sedimentary evolution for future well planning.