Zhao, Ruidong (RIPED, CNPC) | Shi, Junfeng (RIPED, CNPC) | Zhang, Xishun (RIPED, CNPC) | Li, Jinya (China University of Petroleum) | Peng, Yi (RIPED, CNPC) | Xiong, Chunming (RIPED, CNPC) | Liu, Meng (RIPED, CNPC) | Deng, Feng (RIPED, CNPC) | Song, Shenggang (Daqing Oilfield Company, CNPC) | Miao, Guojing (Daqing Oilfield Company, CNPC)
With the continuously progressing of building the intelligent oilfield and the rapid development of the Internet of Things and big data technology, the emerging technologies such as the information acquisition, distributed computing and data mining lead to unceasing innovation in the research and development and management approaches of enterprises. A technical revolution also occurs in the petroleum industry. At present, one of the challenges we are facing is how to keep the advantages of the conventional oil and gas production and combine them with the big data analysis to better serve the petroleum industry. Given the complexity and uncertainty and thus difficulty endowed in the conventional oil and gas production, one potential solution, based on the big data mining, is proposed. The big data clustering analysis can be used to evaluate the oil well, and the multi-variable sensitivity analysis can be visualized through the dimensionality reduction. Data processing, operation condition diagnosis, forecasting and warning, and multi-dimension multi-variable visualization analysis are the main functions that are achieved in our preliminarily-built big data analysis platform for the production of oil and gas wells. In the future, this platform will gradually transform form the "business model" into the "data model", which adopts various methods such as the statistical analysis, pattern recognition, clustering analysis and visualization to enable the intelligent diagnosis, forecasting and warning, and decision-making optimization and evaluation for the oil and gas well production, on the basis of the multi-dimension multi-source data. At last, it is anticipated that this platform should serve the oil and gas production and evolve into an effective method to improve the production, reduce energy consumption and decrease cost for the oilfield.
Shi, Junfeng (RIPED, CNPC) | Chen, Shiwen (RIPED, CNPC) | Zhang, Xishun (RIPED, CNPC) | Zhao, Ruidong (RIPED, CNPC) | Liu, Zhaoyu (Drilling & Production Engineering Department of Jilin Oilfield Company, CNPC) | Liu, Meng (RIPED, CNPC) | Zhang, Na (RIPED, CNPC) | Sun, Dakui (Drilling & Production Engineering Department of Jilin Oilfield Company, CNPC)
The best artificial lifting method for a well is to lifting more with less during the whole life cycle, however, it is difficult to select the best method because there are many factors affecting the choice of artificial lifting methods and most factors cannot be described with mathematical models. At present, the selection mainly depends on experts’ experience, which results in many incorrect decisions and lead to huge economic loss. In China, there are a large number of artificial lifting wells, and the large amount of data generated by the wells is of great value, which can be used to select the best artificial lifting method for different type of oil wells. This paper selects 11 parameters, including well fluid characteristics, fluid production capacity, well trajectory, pump depth, pump efficiency, pump inspection period, and maintenance cost per year as influence factors. About 40,000 artificial lifting wells of CNPC were selected as the big data analysis sample initially. As not all the wells are good samples, an effect evaluation function is established by taking pump efficiency, power consumption with lifting per ton liquid 100m, annual operating maintenance cost into account, then the samples are selected further according to the value of effect evaluation function, which ensured all the samples participated in machine learning are good samples. A deep recurrent neural network was established which can select the best artificial lifting method through deep learning. Experimental results showed that the neural network model had fast convergence and high prediction accuracy. With the application of this model, artificial lifting method selecting and effect analysis have been conducted for more than 5,000 oil wells of CNPC with different reservoir characteristics, different wellbore structures and different fluid characteristics. The coincidence rate between calculation results of this model and actual production situation is 90.56%. Big data analysis provides a reliable, practical and intelligent method for optimizing and selecting artificial lift.
Zhao, Ruidong (RIPED, CNPC) | Li, Jinya (China University of Petroleum) | Tao, Zhen (RIPED, CNPC) | Liu, Meng (RIPED, CNPC) | Shi, Junfeng (RIPED, CNPC) | Xiong, Chunming (RIPED, CNPC) | Huang, Hongxing (NCCBM) | Sun, Chengyan (Daqing Oilfield Company, CNPC) | Zhang, Yufeng (RIPED, CNPC) | Zhang, Xiaowen (RIPED, CNPC)
With the development of many kinds of oilfields, deep well, high deviated well and cluster well are increasing rapidly. Sucker rod pumping still remains a major artificial lift method. There are such problems as severe rod/tubing wearing and shortened rod/tubing life in high deviated rod-pumped wells, and the mechanism and prevention of rod/tubing wearing have not been understood properly.
In order to understand the mechanism of rod/tubing wearing, a lateral load calculation model of rod/tubing is solved in this paper. The calculation results show that both the magnitude and direction of lateral force change dynamically with time and space in one stroke cycle. To better describe the rod/tubing wearing phenomenon, the lateral load is divided into two parts: the primary normal vector related to wellbore trajectory and axial force, and the secondary normal vector only related to wellbore trajectory and invariant with time.
The three-dimensional and dynamic nature of lateral force can account for the rod/tubing wearing partially. The results of mathematical model show that the magnitude of lateral force at the same depth may differ greatly at different times, and its direction may also change periodically. It is likely to be bidirectional rod/tubing wearing when the primary normal force direction changes periodically. Simulation results show that the direction of lateral force is very likely to change periodically below the neutral point of rod string. This finding has accounted for the common double-faced and multi-faced rod/tubing wearing on the lower rod string. The periodic change of lateral force direction will cause rod/tubing collision, which is also an important cause for the rod/tubing wear below the neutral point. It is assumed qualitatively that the production parameters such as pump depth, stroke, stroke frequency and pump diameter are the major factors of the rod/tubing wearing according to field experience. In this paper, mathematic model is used to analyze the impact of these parameters on lateral force and the quantitative analysis is also conducted which provide theoretical foundation for the design of anti-wear production parameters.
The mathematic model and method proposed in this paper are favorable to better accounting for the important phenomenon of rod/tubing wearing in rod-pumped deviated wells. They are capable of the quantitative calculation of lateral forces under different parameter conditions and the anti-wear design. This model has been applied to hundreds of highly deviated wells at Jidong Oilfield, prolonging rod/tubing life 58 days in average.
The development of a new low-carbon operation mode of artificial lift in high-water-cut oilfields, is significant for reducing energy consumption, improving operation efficiency and lowering production costs of oilfields. The annual electric consumption of the oilfield is increasing year by year. In 2016, the total electric consumption exceeded 35 billion kWh, of which the mechanical production system accounts for 57%.
The rodless artificial lift eliminates the use of the sucker rod, and reduces the installed motor power over 50%. The electric consumption is greatly decreased, while tremendous gain is seen in the system efficiency. Moreover, the application performance is especially good for low-production wells. Under such circumstances, the operation cost of the oilfield declines. The current rodless artificial lift is basically based on two types of pumps, namely submersible plunger pump and submersible direct-drive screw pump.
The submersible plunger pump lifts liquid via vertical reciprocation of the moving body driven by the motor, with daily electric consumption of an individual well decreasing by 46%, from 133.4 kWh to 72.5 kWh. The reduced annual electric cost per well is RMB 14,000, and the annual single-well carbon emission falls by 17.5 tons. As for the submersible direct-drive screw pump, the rotation of the pump is directly motivated by the downhole submersible motor, through which the downhole liquid is elevated to the surface. The daily electric consumption of an individual well decreases by 38.4%, from 224kWh to 138kWh, contributing to the annual electric cost reduction per well of RMB 13,600 and annual carbon emission decline per well of 17.1 tons.
The application of the two types of rodless artificial lift has taken initial shape. The submersible plunger pump has been applied to over 200 wells, and the submersible direct-drive screw pump, over 60 wells. The new low-carbon operation mode of artificial lift is critical for the energy saving, efficiency improvement and consequent cost reduction of oilfields, particularly in cases of the industry downturn triggered by low oil prices.
Song, Jianyong (RIPED, CNPC) | Li, Jinsong (RIPED, CNPC) | Zheng, Xiaodong (RIPED, CNPC) | Xie, Zhanan (RIPED, CNPC) | Wang, Daxing (Research Institute of CPOCC) | Wang, Guanchao (China University of Petroleum-Beijing)
Summary The elastic reflection travel-time inversion (ERTI) based on conventional elastic wave equations obtains low wave number components in the model parameters by using travel-time and reflected wave information. However, the coupling effect between the PS waves and the sensitivity of velocities to wave fields enhance the nonlinear problem of inversion. Therefore, in this paper, the reflection traveltime inversion based on the decoupled elastic wave equations is studied, and an improved time-shift crosscorrelation objective function is proposed to implicitly calculate the relative time shift in image domain respectively. The coupling between PS waves is greatly reduced and the inversion results of low wavenumber components are improved. Finally, the Marmous II model tests prove the correctness of this method.
Xu, Feng (RIPED, CNPC) | Yu, Wei (The University of Texas at Austin) | Li, Xiangling (RIPED, CNPC) | Miao, Jijun (SimTech LLC, The University of Texas at Austin) | Zhao, Guoliang (RIPED, CNPC) | Sepehrnoori, Kamy (The University of Texas at Austin) | Li, Xianbin (RIPED, CNPC) | Jin, Jianli (RIPED, CNPC) | Wen, Guangyao (CNPCIC)
Natural fractures are the main producibility factor in the weathered granite reservoirs (basement rock) and volcanic-rock reservoirs. Production practices show that these reservoirs could have high production rate, but the difference of well productivity between single wells is obvious. These reservoirs have complex natural fractures oriented at medium-high angles, which could bring high complexity and heterogeneity to the reservoirs, adding anisotropy to reservoir permeability. It is very hard to effectively simulate complex fractures in naturally fractured reservoirs and study the applicability of different well type and well pattern by using common reservoir simulators. A fast EDFM (Embedded Discrete Fracture Model) method was put forward for production simulation of complex fractures in naturally fractured reservoirs. The EDFM processor combining commercial reservoir simulators (ECLIPSE or CMG) is fully integrated to forecast production performance of the weathered granite reservoir. With a new set of EDFM formulations, the non-neighboring connections (NNCs) in the EDFM are converted into regular connections in traditional reservoir simulators, and the NNCs factors are linked with gridblock permeabilities. So complex dynamic behaviors of natural fractures can be captured, which can maintain the accuracy of DFMs (discrete fracture models) and keep the efficiency offered by structured gridding. In this paper, a 3D model with complex natural fractures was built to model the performance of different well types and well patterns. The results show that wells with higher density of natural fractures produce higher oil production, and horizontal wells with higher density of natural fractures have larger oil production than vertical wells because horizontal wells have a larger contact area than vertical wells. What’s more, heterogeneity and anisotropy have a great effect on well pattern and well type, which need to be studied carefully in the oilfield development.
In 2008, We presented a paper "Application of Temperature Observation Wells during SAGD Operations in a Medium Deep Burial Extra Heavy Oil Reservoir" at the Petroleum Society's 59th Annual Technical Meeting. After 10 years SAGD technology is already widely adopted in exploiting extra heavy oil in China. This paper summarizes the experience on surveillance of SAGD project in the past years.
During SAGD process the adjustment of steam chamber in both vertical and horizontal direction and operation parameters should base on synthetic surveillance data. In the past, the surveillance approach is very limited and the results cannot be used as effective indicators. The successful application of reservoir based synthetic surveillance approach produced reliable data for management of SAGD project in Du 84 block Liaohe Oil field. The applied technical series include pressure/temperature observation wells, pressure/temperature monitoring in horizontal wells, time-lapse seismic monitoring, micro-gravity test etc. With the help of these monitoring data, the accurate and long term effective database was established.
The application of synthetic monitoring system provides the opportunity of accurate control of steam injection and production. The temperature and pressure observation well can monitor the vertical development of steam chamber, especially in gas-SAGD process. The observation well can detect the vertical sweep area of injected gas which can give effective approach in SAGD management. The temperature and pressure monitoring and tracer test can provide information for connection between injector and producer. 4-Dimensional seismic and 4-Dimensional micro gravity is a new approach of combination for petro-physical technology and petroleum development. 4D seismic not only can remap the geological body but also it can depict the steam chamber distribution in the reservoir. 4D micro gravity monitoring can accurately detect the front of steam chamber. With these data, the distribution of steam zone and residual oil is clear for future reservoir management.
This paper gives a verified approach of surveillance and the corresponding operation adjustment. And this can be guidance for design and application of new SAGD surveillance system.
Liu, He (RIPED, CNPC) | Zhang, Shaolin (RIPED, CNPC) | Sun, Qiang (RIPED, CNPC) | Li, Tao (RIPED, CNPC) | Ming, Eryang (RIPED, CNPC) | Huang, Shouzhi (RIPED, CNPC) | Han, Weiye (RIPED, CNPC) | Chen, Qiang (RIPED, CNPC) | Li, Yiliang (RIPED, CNPC) | Pei, Xiaohan (RIPED, CNPC)
After long-term water-flooding, many of the matured fields in China have experienced changes in the physical properties of reservoirs. Moreover, the inefficient cycle of water flooding in the reservoirs is serious, and the heterogeneity of reservoirs causes difficulty to determine the distribution of remaining oil. It is impossible to reflect the real situation of the stratum only by simulation analysis with the numerical simulation software. To core in a specific location through coring technology and analyze the core can not only re-conduct a more accurate evaluation of the stratum, but also can modify relevant data of existing models to improve the simulation accuracy. But the current technology can’t conduct coring operations near wellbore and in deep parts.
Therefore, based on the ultra-short radius sidetracking technology, this paper aims to develop ultra-short radius flexible sealed coring technology to achieve coring outside the casing. Compared with the ultra-short radius sidetracking technology, the ultra-short radius flexible sealed coring technology has, in addition to the windowing, deflecting, and horizontal drilling tools, the core tools of this technology, that is, the flexible sealed coring tool. The tool is mainly composed of a flexible outer cylinder and a highly elastic titanium alloy inner cylinder. The flexible outer cylinder is connected by a multi-section of flexible units that can be bent up to 5°. And a special coring bit is connected to the front of the tool. The maximum length of the core taken in a single coring process is 1.1 meters; the core diameter is up to 40mm. By using this technology, the minimum horizontal distance of the core position and the borehole wall is 0.8 meter, and the maximum horizontal distance can be up to 100 meters.
At present, the technology has been successfully applied to more than 10 wells, and the average core recovery rate has reached 90%, which provides valuable data for the geological departments and is of great significance for re-developing matured fields.
This technology can obtain the core from outside of the casing and near wellbore, and offers a more accurate evaluation on changes of physical properties of the reservoirs, providing the basis for adjusting the subsequent water flooding development plans.
The technological advances for fracturing and horizontal well makes it viable to achieve unconventional hydrocarbons reserves developing commercially. Underground water, soil and environmental protection are currently major issues when unconventional hydrocarbons extracted. Liquid CO2 fracturing instead of the hydraulic fracturing for oil field stimulation is an effective way for water resource protection, pollution reduction, greenhouse emission reduction.
According to the current technologylever, liquid CO2 fracturing cannot reach the same fracture generation ability as the conventional fracturing, so the approach has been proposed and implemented to collaborate fracturing and pressure support to improve production performance by liquid CO2 injection in the low-permeability reservoir. An important part of the approach is that significant amount of injected CO2 is dissolved in remaining oil, similarly CO2 huff-puff, contributing to oil recovery enhancement, some will beproduced and needed to be cycled.
The methodologyis proposed in this paperto obtain the volume of CO2 storage at different fracturing scales for liquid CO2 fracturing by employing thecompositional simulation in low-permeability reservoir in Jilin Oilfield. A high-resolution geological model based on geological, geophysical, production and liquid CO2 fracturing data from H Block in Jilin Oilfield is usedin the study. The dynamic model is calibrated to the reservoir's history performance as a benchmark for the study. Several models represented the different fracturing scales are generated and the storage capacity is analyzed as a function of CO2 injection volume, soak time, pressure and oil productivity.
The study data show that the CO2 storage volume decreases as the length and conductivity of fracture increases. As a result, CO2 storage ratio is 0.218 if fracture with half length is 100m and permeability is 100md, CO2 storage ratio is 0.67 if no fracture exists. This goes toward creating gas separation and recycling injection device for large-scale liquid CO2 fracturing concerning CO2 zero emission.
The research has been noteworthy in its explicit recognition of the need for CO2 recycling during liquid CO2 fracturing by simulation of CO2 storage capacity. Pressure swing adsorption method will be introduced by great change of CO2 concentration of the produced gas from the simulation result.
This paper demonstrates successful application of parallel appraisal and development in G field, Niger. G field is a complicated stacked light oil reservoir with gas cap in its E2 major pool. After current operator's takeover in 2008, the government required realization of 10 KBOPD in this field within 3 years, leaving only 1 year for appraisal and development as field construction in this landlocked country at least takes 2 years. Whereas there was only 2D seismic and one well data (G-1) with RFT and testing, parallel appraisal and development strategy must be adopted and following 2 major challenges were identified: 1) Limited data and great uncertainties in gas-cap and well productivity; 2) development decision-making along with appraisal process.
Appraisal and development have been optimized by following approaches: 1) RFT and wireline data were fully studied to identify oil-gas-contact in E2 pool and indicate possible oil in E3 pool; 2) appraisal wells placement based on new 3D seismic; 3) identify key uncertain development parameters and combine into appraisal campaign targets to gradually reduce uncertainties.
Appraisal well G-2 confirmed the separation of block G-1 and G-2. The second appraisal well G-3 confirmed oil-gas-contact, encountered oil zone in lower E3 pool. The third appraisal well G-8 encountered oil zone in E2 and further firm up gas-cap area, laying firm foundation for subsequent development well placement.6 producers were placed out of gas cap and appraisal wells were transferred to development wells, all successfully commissioned in 2011, achieving desired production target.
Conclusions drawn from successful parallel appraisal and development application were:1) utilization of all data available contributed to correct appraisal decision-making; 2) Combining 3D and appraisal well findings help reduce geological uncertainties; 3) Identify and reduce key development uncertainties during appraisal speed up appraisal process. For complicated fields at appraisal stage, the methodology in this paper is of strong reference value.