Tian, Hua (Research Inst Petr Expl & Dev, Petrochina) | Zou, Caineng (Research Inst Petr Expl & Dev, Petrochina) | Liu, Shaobo (Research Inst Petr Expl & Dev, Petrochina) | Zhang, Shuichang (Research Inst Petr Expl & Dev, Petrochina) | Lu, Xuesong (Research Inst Petr Expl & Dev, Petrochina) | Ma, Xingzhi (Research Inst Petr Expl & Dev, Petrochina) | Bi, Lina (Research Inst Petr Expl & Dev, Petrochina) | Yuan, Miao (Research Inst Petr Expl & Dev, Petrochina)
A series of petrohysical experiments have been conducted to obtain the gas physical properties (e.g., gas-water interfacial tension). The capillary pressures of pore throats were obtained through numerical calculation. Furthermore, residue water was used to calculate gas/water saturation in the reservoirs. The gas saturation variation under lower interfacial tension and the amount of gas lost during the uplift in burial history need an in-depth examination (Tian et al., 2017). In addition to the geological studies in the field, various laboratory methods were used to tackle the problems mentioned above, including Nlear nuclear magnetic resonance (NMR) and fluid inclusion analysis with optical and Laser Raman spectroscopy. During the charging history, hydrcarbon saturations at different temperature and pressure was calculated using the model established in this paper, which is mainly determined by the pore size distribution obtained by the NMR analysis. The charging pressure is measured by fluid inclusion study with optical and Laser Raman spectroscopy test. Furthermore, the leakage content of gas during the burial history was calculated using a diffusion model (Krooss& Leythaeuser., 1988; Krooss et al., 1992).
Chen, Changzhao (State Key Laboratory of Petroleum Pollution Control, CNPC Research Institute of Safety and Environmental Technology) | Li, Xingchun (China University of Petroleum) | Wu, Baichun (State Key Laboratory of Petroleum Pollution Control, CNPC Research Institute of Safety and Environmental Technology) | Zhang, Kunfeng (State Key Laboratory of Petroleum Pollution Control, CNPC Research Institute of Safety and Environmental Technology) | Song, Quanwei (State Key Laboratory of Petroleum Pollution Control, CNPC Research Institute of Safety and Environmental Technology)
The world has seen a peak in unconventional gas development in recent years. Based on the practice of unconventional gas field development domestic in China and abroad, it is risky that the reinjection water may contaminate groundwater in local or adjacent areas during reinjected fluid migration. Ensuring environmental safety of the reinjection is a multi-disciplinary system project. This paper carries out the analysis and shares the experience of China's practice based on the actual cases from the following aspects. 1) The screening of the well location and the formation of the reinjection. 2) The drilling and cementing construction of the reinjection well, which considers the factors such as cementing quality and cement height and casing material. 3) The estimation of the total reinjection capacity, and the factors such as porosity and permeability of the geologic trap and reservoir fracture pressure is considered. 4) The monitoring of well and migration of reinjection fluids. Further environmental risk study of produced water reinjection is presented in this paper, on both sandstone formation of tight sand gas field and carbonate karst formation of shale gas field in China's typical unconventional gas development areas, using laboratory geochemistry experiments and large area geophysical test to obtain seismic data.
Zheng, Ma Jia (Southwest petroleum University) | Liu, Xin (Schlumberger Technology Services, Chengdu, Ltd) | Zhao, Jian Ping (PetroChina Southwest Oil and Gas Field Company) | Qiu, Xun Xi (Sichuan Shale Gas Exploration and Development Company Ltd) | Fang, Jian (CCDC Geological Exploration & Development Research Institute) | Wang, Xiong Fei (Schlumberger Technology Services, Chengdu, Ltd) | Zhao, Jing Kai (Schlumberger Technology Services, Chengdu, Ltd) | Geng, Gan (Schlumberger Technology Services, Chengdu, Ltd)
The Sichuan Basin is the major target for shale gas exploration in China because of its rich gas stored in unexploited black shale with multiple bed series. National Shale Gas Exploitation Areas have been established since 2012, the proved geological shale gas reserves is 9210×108 m3 and 90.25×108m3 annually output has been achieved by the end of 2017.
The operating Sichuan Basin shale gas area located in the major compression tectonic experienced multiple geological structure movements in Earth history, showing characteristics of high steep structure with faults greatly developed. It's proven that the key factors in exploiting these targets are well acknowledged by the efforts to land and expose the lateral within the sweet zone. To successfully place lateral in reservoirs from geological perspective must overcome challenges of high uncertainty structure identification to make soft landing and maximize horizontal exposure in the sweet zone.
While it comes to shale gas reservoir, to pave the way for fracture operation and achieve good well completion, the drilling requires a relative gentle well path, keeping well path inclination with limitation, which requires to make azimuth turning to achieve this.
To ensure the optimum placement of the well in sweet zone, the integration of rotary steerable drilling system (RSS) with borehole images measurements in real-time have been implemented with the employment of well placement technique.
The borehole image portrays structural profile while drilling whilst the rotary steerable drilling system provides accurate trajectory control. With the help of borehole image and proactive log correlation, the trajectory can be landed precisely into desired best quality reservoir, although the formation dip and actual target depth become much different with geological prognosis. During the lateral section, the trajectory was also controlled effectively in the high-quality reservoir despite of structural variation and reservoir property change. Through use of Fit-For-Purpose solution it effectively improves drilling efficiency and positively impacts well production. These achievements subsequently help to optimize wells deployment plan and wells with longer lateral horizontal section were planned for greater predictable production rate.
Xue, Ming (State Key Laboratory of Petroleum Pollution Control, CNPC Research Institute of Safety and Environmental Technology) | Fan, Jun-xin (State Key Laboratory of Petroleum Pollution Control, CNPC Research Institute of Safety and Environmental Technology) | Weng, Yi-bin (State Key Laboratory of Petroleum Pollution Control, CNPC Research Institute of Safety and Environmental Technology) | Cui, Xiangyu (State Key Laboratory of Petroleum Pollution Control, CNPC Research Institute of Safety and Environmental Technology) | Li, Xing-chun (State Key Laboratory of Petroleum Pollution Control, CNPC Research Institute of Safety and Environmental Technology)
Objectives/Scope: Greenhouse gas emission (carbon dioxide and methane, etc.) during shale gas production could decide whether it is a cleaner energy source than coal. However, the methane and carbon dioxide emission from flowback process during shale gas production remains unclear. The withdrawn of fracture water both from underground and surface water, and the relatively high gas pressure from the wellhead have made flowback water highly potential as a significant greenhouse gas emission source.
Methods, Procedures, Process: In this study, the estimation of greenhouse emission potential was provided based on the flowback water samples collected from shale production sites of China. The buffer capacity of carbon dioxide was estimated based on the parameters measured including temperature, pressure, conductivity, salinity, dissolved inorganic carbon (DIC), pH, chloride etc. The possible methane emission was also estimated based on the solution/dissolution curve from gas-water equilibrium during the flowback process.
Results, Observations, Conclusions: The results showed that: the relatively high salinity of the flowback water has provided a considerable buffer capacity for carbon dioxide. The water residence time in the water tank/pond largely determines air-water greenhouse flux. When the flowback water pass through the three-phase separator to the water outlet, the dissolution capacity of methane reduced sharply dropped. By switching to a higher water level in the separator, methane emission could be reduced. However, a higher water vapor ratio may be detected in the gas phase, as well. Besides the fugitive methane emission from pneumatic pumps, valves, etc., greenhouse gas emission from flowback water is a significant source which needs to be reduced in future shale gas production.
Novel/Additive Information: The determination of greenhouse gas emission from flowback could better defined the life cycle of shale gas, while provide baseline analysis for the development of greenhouse gas control technology during flowback water treatment and three-phase separator optimization.
Zhai, Wenbao (China University of Petroleum) | Li, Jun (China University of Petroleum) | Xi, Yan (China University of Petroleum) | Liu, Gonghui (China University of Petroleum) | Yang, Hongwei (China University of Petroleum) | Jiang, Hailong (China University of Petroleum) | Zhou, Yingcao (CNPC Engineering Technology R&D Company Limited)
Shale reservoir heterogeneity is more and more focused during shale gas development, especially deep shale gas reservoir buried in the depth of over 3,500 m. However, the evaluation methods of heterogeneity are not always available and poor applicability. In this study, a Principle Component Analysis (PCA)-Artificial Neural Network (ANN) model was presented. The evaluation steps of the model were also given. The validation of the model was confirmed by using a deep shale gas well located in Weiyuan area of Sichuan Basin, China. The results of the validation show that the model presented in this study can be in good agreement with the assessed values of heterogeneity obtained from microseimic events. The developed model's effectiveness was tested by comparing the results acquired from ANN without PCA, where the PCA reduces the dimension of input parameters to improve results of PCA-ANN over 80%. Therefore, the PCA-ANN model can help the engineers evaluate the deep shale reservoir heterogeneity, which provides a tool to give preliminary recommendations of the likelihood of improving the effectiveness of hydraulic fracturing. Implementation of the proposed model can serve as a cost-effective and reliable alternative for the deep shale reservoir.
Chen, Xiaoer (Institute of Sedimentary Geology, Chengdu University of Technology, Geophysical Technology Research Centre, BGP, CNPC) | Fan, Kun (Southwest Geophysical Research Institute, BGP, CNPC) | Ren, Chenghao (Southwest Geophysical Company, BGP, CNPC) | Li, Le (Geophysical Technology Research Centre, BGP, CNPC) | Yan, Zhenqian (Sichuan Institute of Coral Field Geological Engineering Exploration and Designing) | Zou, Guoliang (Exploration Department of Changqing Oilfield LTD, CNPC) | Cao, Zhonglin (Geophysical Technology Research Centre, BGP, CNPC) | Zhao, Yao (Geophysical Technology Research Centre, BGP, CNPC)
The Cambrian Longwangmiao Formation in the Sichuan Basin, southwest China, mainly comprising of dolomites, is one of the most ancient production layer in the world. Recently, Anyue gas field was discovered in the Leshan-longnvsi paleo-uplift in the central Sichuan Basin, and become the oldest gas field in the carbonate rocks in a single structural system in China. The reservoir is mainly distributed in the shoal grain dolomite, which is always controlled by the sedimentary environment. The conventional well correlation and sedimentary facies analysis might result in difficulty of carbonate shoals distribution and reservoir description in the gas field. Hence, how to characterize the geometry and distribution of carbonate shoals is critical for gas exploration and development. In our study, we completed an interpretation of 1172km2 3D seismic data in the field by means of all reflectors auto-tracking method. The method, combining density-based spatial clustering with waveform similarity clustering algorithm, can automatically track and interpret all reflectors within the 3D seismic cube. As a result, 18 local horizons, characterized by a shingled progradational configuration, were recognized within the Longwangmiao Formation. Synthetic seismograms suggest that these parallel oblique progradational sets were considered as carbonate shoals. The Longwangmiao Formation is consisted of stacked multistaged carbonate grainstones deposited on the shoals within the platform. These shoals, which grow towards northwest, are approximately distributed surrounding the Leshan-Longnvsi paleo-uplift. Stacked and widely distributed shoal grainstone reservoir is formed on the uplift. Our study suggests that the paleo-uplift mainly controls the shoal distribution in the study area, which provides important clues for gas exploration.
Is Surfactant Environmentally Safe for Offshore Use and Discharge? The current presentation date and time shown is a TENTATIVE schedule. The final/confirm presentation schedule will be notified/available in February 2019. Designing Cement Jobs for Success - Get It Right the First Time! Connected Reservoir Regions Map Created From Time-Lapse Pressure Data Shows Similarity to Other Reservoir Quality Maps in a Heterogeneous Carbonate Reservoir. X. Du, Y. Jin, X. Wu, U. of Houston; Y. Liu, X. Wu, O. Awan, J. Roth, K.C. See, N. Tognini, Shell Intl.
By International Petroleum Technology Conference (IPTC) Monday, 25 March 0900-1600 hours Instructors: Olivier Dubrule and Lukas Mosser, Imperial College London Deep Learning (DL) is already bringing game-changing applications to the petroleum industry, and this is certainly the beginning of an enduring trend. Many petroleum engineers and geoscientists are interested to know more about DL but are not sure where to start. This one-day course aims to provide this introduction. The first half of the course presents the formalism of Logistic Regression, Neural Networks and Convolutional Neural Networks and some of their applications. Much of the standard terminology used in DL applications is also presented. In the afternoon, the online environment associated with DL is discussed, from Python libraries to software repositories, including useful websites and big datasets. The last part of the course is spent discussing the most promising subsurface applications of DL.
Zhai, Wenbao (China University of Petroleum) | Li, Jun (China University of Petroleum) | Chen, Zhaowei (CNPC Engineering Technology R&D Company Limited) | Zhou, Yingcao (CNPC Engineering Technology R&D Company Limited)
Many weakness planes (such as faults, joints, and micro-fractures, etc.) are usually pre-existed in rock. However, the stress statement changed by hydraulic fracture (HF) propagation may have an important impact on hydraulic fracturing, which is closely related to stress statement of weakness planes. Firstly, the rock samples containing the pre-existing weakness planes were analyzed according to the curves of volumetric strain versus stress difference acquired by laboratory experiment. Secondly, the effective normal stress and shear stress of weakness planes were calculated by the tensor transformation method. And then, weakness planes were divided into four kinds according to the relationship between stress statements of weakness planes and failure lines of Mohr diagram and the kinds of weakness planes were visually described in the Mohr diagram. Finally, it was respectively discussed that pre-existing weakness planes did have an influence on hydraulic fracturing under different stress statements. The research results show that when the effective stress is more than zero, with the effective stress decrease, weakness planes are the more easily inclined to become the dilatation phenomenon where the self-propping effect can improve the reservoirs permeability due to surface asperities of weakness planes. However, there are very complex mechanical phenomena induced by weakness planes under higher effective stress. When hydraulic fractures encounter the pre-existing weakness planes under the approximate stress statement, it may be easy to occur shear slipping of weakness planes or it is difficult to be opened by hydraulic fractures. The latter is extremely beneficial to not become the maximum simulated reservoir volume (SRV) and should be avoided by fracturing operation as early as possible. It is somewhat different that the influence of different mechanical phenomena on hydraulic fracturing, which has a certain guidance for improving hydraulic fracturing stimulation.
Compared to the conventional oil and gas resources, there is usually not natural production in unconventional oil and gas resources, and it needs to rely on hydraulic fracturing to improve development effectiveness (Shrivastava and Sharma, 2018). The complex fracture networks may be created in hydraulic fracturing, which is a combination of shear and tensile failures (Lin et al., 2018). The shear failure of weakness planes (such as faults, joints, and micro-cracks, etc.) resulted in long-term geological tectonic movement is anticipated to dominate in hydraulic fracturing. However, it is a fact that rock dilatation may be caused by rock plastic behavior that the horizontal stress is balanced by the pressure near the fractures tip in hydraulic fracturing (Alko and Economides, 1995). With the development of unconventional oil and gas resources, these weakness planes are a double-edged sword that they can act as a good oil and gas flowing channel, but they can also lead to hydraulic fracturing failure (Ye, 2017). Therefore, it is necessary that considering the role of weakness planes in hydraulic fracturing will be used to optimize the hydraulic fracturing design.
Yu, Hao (Southwest Petroleum University and Pennsylvania State University) | Dahi Taleghani, Arash (Pennsylvania State University) | Gonzalez Chavez, Miguel (Petroleos Mexicanos) | Lian, Zhanghua (Southwest Petroleum University)
Microseismic data and post-fracturing production have confirmed the positive role of fracture complexity on production enhancement in fractured wells. While operators are looking for different fluids and pumping schedules to enhance fracture complexity, the mechanisms ruling the process is not fully understood. This paper provides a comprehensive workflow to model the fracture pattern development by accounting for interactions with numerous natural fractures. We present a robust finite element model with adaptive insertion of three-dimensional cohesive elements for fracture propagation through the intact rock as well as the network of intersecting natural fractures. Cohesive elements are coupled with general Darcy's flow to incorporate fluid flow as well as elastic and plastic deformations of rock during initiation, propagation and closure of hydraulic fractures. Hydraulic fracturing treatment has been simulated for different natural fracture patterns. Fluid injection pressure fluctuations are observed while reopening natural fractures. The impact of operation schedules on network complexity such as hesitation time is investigated. The complexity of fracture network is characterized by the ratio of total fracture length to its effective radius from the wellbore. Our analysis has shown that in addition to the differential stress and the fracture intersection angle which are already determined by the nature, pumping injection rate and hesitation time can play a significant role in fracture branching and its diversion to different natural fracture sets. Higher injection rate is found to have a positive effect to overcome the resistance of natural fractures in different directions, and hesitation in the middle of pumping can force the fracture to divert into other directions, both of which help develop a more complex fracture pattern.