Deng, Song (Changzhou University) | Liu, Yali (Changzhou University) | Wei, Xia (No. 2 Gas Production Plant, Changqing Oilfield Company, PetroChina) | Tao, Lei (Changzhou University) | He, Yanfeng (Changzhou University)
Phase change, a major factor that restricts the development of gas hydrate, is likely to cause blockage in well completion section (sieve section - wellbore lifting section), thus resulting in the engineering losses. In view of the defects in the previous studies on the confluence mechanism of completion section of gas hydrate pressure drop method mining under openhole completion technology, the flow of gas hydrate in the well completion section was simplified as the Main-Branch pipe confluence model in this paper. Firstly, a physical model was established. On the basis of the energy conservation law and the Peng-Robinson equation, the temperature and pressure coupling model was also derived. Then, the Fluent software was used to simulate the temperature gradient and pressure gradient changes in the Main-Branch model. The gas hydrate phase diagram and PT environment under different velocity were obtained. Finally, the contrast analysis between theoretical model and numerical simulation was carried out and the established model was verified. Through the study of this paper, it is possible to prevent blockage of the well completion section by means of depressurization, which can provide theoretical guidance for the control of pressure drop when gas hydrate is extracted by depressurization. It is important for the exploitation and continuous production of gas hydrate in the later stage.
Wang, Xiang (Changzhou University) | He, Yanfeng (Changzhou University) | Li, Fajun (Luming Oil and Gas Exploration and Development Co., LTD) | Dou, Xiangji (Changzhou University) | Wang, Zhen (Luming Oil and Gas Exploration and Development Co., LTD) | Xu, Hui (Changzhou University) | Fu, Lipei (Changzhou University)
Monitoring the working conditions of the sucker rod pumping wells in a timely and accurate manner is important for oil production. With the development of smart oil fields, more and more sensors are installed on the well. The variety and volume of the monitoring data are big. The oilfield big data can be utilized to improve the diagnostic performance. In this work, we aim to utilize the big data collected during oil well production and a deep learning technique to build a new generation of intelligent diagnosis model to monitor working condition of sucker rod pumping wells. Over 5 million of well monitoring records, which covers information about one year of an oil field block, are collected and preprocessed. To show the dynamic changes of the working conditions for the wells, the overlay dynamometer card is proposed and plotted for each data record. The overlay dynamometer card stacks two dynamometer curve at different times. Based on the overlay dynamometer cards, the working conditions are divided into 30 types, and the corresponding dataset are created. An intelligent diagnosis model using the convolutional neural network (CNN), one of the deep learning framework, is proposed. By the convolution and pooling operation, CNN can extract features of an image implicitly without human effort and prior knowledge. That makes CNN very suitable for the recognition of the overlay dynamometer cards. The architecture for working condition diagnosis CNN model is designed. The CNN model consists of 14 layers with six convolutional layers, three pooling layers, and three fully connected layers. The total number of neurons is over 1.7 million. The overlay dynamometer card dataset is used to train and validate the CNN model. The accuracy and efficiency of the model are evaluated. Both the training and validation accuracies of the CNN model are over 99% after ten training epochs. The average training elapsed time for an epoch is 8909.5 seconds and the average time to diagnosis a sample is 1.3 milliseconds. Based on the trained CNN model, a working condition monitoring software for suck rod pumping well is developed. The software runs 7×24 hours to diagnosis the working conditions of wells and post warning to users. It also has a feedback learning workflow to update the CNN model regularly to improve its performance. Through 3 months of on-site test run show that the actual accuracy of the CNN model is over 90%.
Jiang, Long (China University of Petroleum) | Cheng, Yuanfang (China University of Petroleum) | Han, Zhongying (China University of Petroleum) | Gao, Qi (China University of Petroleum) | Yan, Chuanliang (China University of Petroleum) | Wang, Guihua (China University of Petroleum) | Wang, Huaidong (CCCC Marine Construction & Development Co., LTD) | Fu, Lipei (Changzhou University)
With the application of hydraulic fracturing in unconventional gas reservoirs, large-scale fracturing operations have resulted in water shortage and environmental pollution. Many scholars and governments gradually began to explore many waterless fracturing technologies in recent years, such as high-energy gas fracturing, liquefied petroleum gas fracturing, nitrogen foam fracturing, liquid/supercritical CO2 fracturing, and cryogenic fracturing using liquid nitrogen (LN2), etc. As a waterless fracturing technology, LN2 fracturing can significantly improve the coalbed methane and shale gas wells production, greatly improving the effectiveness of reservoir stimulation. But the efficiency mechanism and influencing factors of LN2 fracturing were still not clear in well bottom conditions. To investigate the influence of LN2 treatment on pore characteristics and carrying capacities of anisotropic shale, the shale from the Longmaxi formation in Chongqing, China, was selected as samples for LN2 treatment experiment. A series of permeability, ultrasonic wave, nuclear magnetic resonance (NMR) and triaxial compression experiments were conducted on different bedding shales. In pore structure tests, the increasing range of permeability is 8.01% – 74.36%, and the P-wave velocity decreases by 4.06% – 16.08%; in NMR tests, the morphology of transverse relaxation time (T2) distribution curves for LN2 treatment samples was significantly different than that of the original sample. Moreover, the change of the saturated sample is greater than that of the dry sample. In triaxial compression tests, the compressive strength, elastic modulus and brittleness of the shale were generally lower for all treated samples with LN2. The study results indicate that LN2 can cause serious irreversible damage to the internal structure of shale, which helps to open natural fractures and decrease the initiation pressure of reservoir stimulation. In cryogenic fracturing using LN2, it is of great significance to generate the complex fracture networks and improve the fracturing performance. This fracturing technology plays an important role in the development of unconventional natural gas with a bright future.
Kang, Bo (China University of Petroleum Beijing and Sinopec ShengLi Drilling Research Institute) | Fan, Honghai (China University of Petroleum Beijing) | Liu, Jinge (Sinopec Research Institute of Petroleum Engineering) | Wen, Zixiang (China University of Petroleum Beijing) | Deng, Song (Changzhou University) | Wang, Shujiang (Sinopec ShengLi Drilling Research Institute) | Chen, Yongming (Sinopec ShengLi Drilling Research Institute) | Zhou, Yanjun (Sinopec ShengLi Drilling Research Institute) | Feng, Guangtong (Sinopec ShengLi Drilling Research Institute) | Li, Zongqing (Sinopec ShengLi Drilling Research Institute) | Yan, Xiuliang (Sinopec ShengLi Drilling Research Institute)
When drilling in the open hole with negative density window, which occurs leakage in the upper section and collapse in the lower section, it will lead to many problems using the conventional method to seal the formation with technical casing, such as high cost,complex casing structure and small completion size. It is difficult to meet the needs of low cost and high efficiency development in the deep wells.
This paper presents a new Gas-Lift MPD drilling method based on Dual-Channel compound Drillpipe (DCP), which can solve the above problems. The DCP is composed of the 139.7mm DCP, the gas lift joint and the conventional 139.7mm drill pipe. It has two circulating channels. Channel 1 is for drilling fluid circulation and channel 2 is directly connected with the upper borehole annulus. The advantage of this method is that it can change the upper wellbore annulus into gas-liquid two-phase flow by injecting gas the channel 2 when the drilling fluid is circulating in the channel 1. It can develop different annulus ECD gradient (small to large) profile and complete complex pressure formation drilling operation in the same open hole section.
According to the design of SBX-5H well, the article uses OLGA to carry out dynamic simulation and analysis of the construction plan of the Gas-lift MPD based on Dual-Channel Drillpipe. The simulation results show that it has great advantages in reducing the number of casing layers, shortening the drilling cycle and enlarging the completion size. Firstly, the control requirements of the ECD profileare is satisfied, which is that the ECD<1.28g/cm3 in the upper section and ECD>1.32g/cm3 in the bottom of the open hole (collapse ECD=1.31g/ cm3, leakage ECD=1.29cm3) by simulating and adjusting drilling pump flow, injected gas flow rate, Dual-Channel Dirllpipe length and drilling fluid density. Secondly, the complicated drilling problem is expected to be solved,such as repeated leakage in the long open hole section. The number of casing layers can be further reduced from 4 to 3 and the drilling cycle is expected to be reduced by more than 20%. Finally, the completion well bore size will be expanded from 149.2mm to 165.1mm (enlarged 11%), which can better meet the requirements of the next production and reservoir transformation.
Through the simulation analysis, it is proved that the Gas-lift MPD technology based on Dual-Channel Drillpipe can effectively solve the problem of negative density window in deep well drilling operation. It not only reduces the drilling difficulties and the drilling cycle, but also is economical and efficient. Therefore, it has a good market prospect.
Cobalt-based alloys, though possessing relevant resistance to oxidation and erosion, inevitably encounter corrosion in acidic environments. In this paper, the cobalt-based alloys containing Cr-Ni-Mo- W-Co ingredients were produced by hot isostatic pressing (HIP) method and their corrosion behavior in hydrochloric acid was investigated using potentiodynamic polarization (PDP) curves, electrochemical impedance spectroscopy (EIS) measurements and immersion corrosion tests. Post-test, the alloys surface was characterized by optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD), the ions concentration in corrosion solution was characterized by inductively coupled plasma (ICP). The results indicated that corrosion resistance of three alloys follows the order 3.0Mo > 1.0Mo > 0.5Mo. During corrosion process, constituent Ni, Fe, Cr and Co in base material tend to dissolve preferentially, while carbides precipitates will be protected due to galvanic coupling in hydrochloric acid solution. Different alloy constituents and microstructures will result in different corrosion behaviors.
Owing to the high hardness and good toughness over a wide temperature range, cobalt-based alloys present excellent wear resistance and valued industrial applications, such as cutting tools or structural materials at high temperature . However, they do not show desirable corrosion resistance in harsh corrosive environment. Undergoing corrosion usually deteriorates the surface properties and wear resistance of a tool in service, accelerating its failure . Therefore, it is greatly valued to improve its corrosion resistance and select appropriate materials for service in harsh environment.
The corrosion properties of WC-Co hard-metals received great concern from researchers . A.M. Human etc. have investigated the electrochemical behavior of tungsten carbide based cemented carbides, found that the binder corrodes faster than the carbide and is leached out in spite of exhibiting a pseudopassive behavior . Sutha Sutthiruangwong etc. have examined the corrosion properties of cemented carbides with cobalt binder phase in HCl and H2SO4 solution, found the corrosion resistance of cemented carbide increases with decreasing magnetic saturation, and lower cobalt binder content exhibits better corrosion resistance . S. Hochstrasser etc. have carried a systematic investigation on the corrosion mechanisms of the WC-Co composite in solutions with different pH, they found that the solution pH plays more dominant role on corrosion susceptibility than the specific ions. The corrosion process of WC-Co consists mainly of Co dissolution in neutral and acidic solution, while WC dissolution becomes more significant at alkaline pH . The grain size of WC-10Co alloy influences its electrochemical corrosion behaviors, the alloys with smaller WC grain sizes exhibit better corrosion resistances in solutions of NaOH and Na2SO4, while the alloys with larger WC grain sizes exhibit better corrosion resistance in H2SO4 .