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Natural Gas Hydrate Production Technology and Rock Mechanics in Petroleum...
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Natural Gas Hydrate Production Technology and Rock Mechanics in Petroleum Engineering

A special issue of Processes (ISSN 2227-9717). This special issue belongs to the section "Chemical Processes and Systems".

Deadline for manuscript submissions: closed (28 December 2022) | Viewed by 21623

Special Issue Editors

Dr. Chuanliang Yan

E-Mail Website
Guest Editor
School of Petroleum Engineering, China University of Petroleum (East China), Qingdao 266580, China
Interests: natural gas hydrate production; rock mechanics; hydraulic fracturing; petroleum engineering
Special Issues, Collections and Topics in MDPI journals
Dr. Kai Zhao

E-Mail Website
Guest Editor
College of Petroleum Engineering, Xi’an Shiyou University, Xi’an 710065, China
Interests: rock mechanics; wellbore stability; hydraulic fracturing
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Fucheng Deng

E-Mail Website
Guest Editor
School of Mechanical Engineering, Yangtze University, Jingzhou 434023, China
Interests: natural gas hydrate production; rock mechanics; sand production; petroleum engineering
Special Issues, Collections and Topics in MDPI journals
Dr. Yang Li

E-Mail Website
Guest Editor
School of Petroleum Engineering, China University of Petroleum (East China), Qingdao 266580, China
Interests: natural gas hydrate production; rock mechanics; wellbore stability
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Global natural gas hydrate organic carbon reserves are about twice those of oil, natural gas, and coal combined, making it an important potential efficient clean replacement energy source for oil and gas. In recent years, the United States, Canada, Japan, China, and other countries have carried out natural gas hydrate production tests and achieved a series of advances, vigorously promoting the process of commercial production of natural gas hydrate. However, because of the difficulty of gas hydrate production, it is very important to continue research into its production technology to realize the commercial production of gas hydrate as soon as possible.

With the development of the oil and gas industry to deep and unconventional areas, and the concept of geology-engineering integration, rock mechanics is playing an increasingly important role in solving the problems related to petroleum engineering. At the same time, rock mechanics also play an important role in the production of natural gas hydrate due to the weak cementation characteristics of hydrate reservoirs.

This Special Issue entitled Natural Gas Hydrate Production Technology and Rock Mechanics in Petroleum Engineering seeks high quality work focusing on the latest novel advances in the production technology of natural gas hydrate and rock mechanics in petroleum engineering. Topics include, but are not limited to:

  • New concepts, theories, methods, experiments, and techniques in natural gas hydrate exploration, drilling, and development.
  • Pilot tests and field applications for natural gas hydrates.
  • Geomechanics of the wellbore, the reservoir, or the overlying layers. These problems include wellbore stability, sand production, hydraulic fracturing, and caprock integrity, among others.

Dr. Chuanliang Yan
Dr. Kai Zhao
Dr. Fucheng Deng
Dr. Yang Li
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Processes is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

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15 pages, 8272 KiB  
Article
Research on the Formation and Plugging Risk of Gas Hydrate in a Deepwater Drilling Wellbore: A Case Study
by Haodong Chen, Ming Luo, Donglei Jiang, Yanhui Wu, Chuanhua Ma, Xin Yu, Miao Wang, Yupeng Yang, Hexing Liu and Yu Zhang
Processes 2023, 11(2), 488; https://0-doi-org.brum.beds.ac.uk/10.3390/pr11020488 - 06 Feb 2023
Cited by 1 | Viewed by 1467
Abstract
At present, the formation mechanism of gas hydrate (hereinafter referred to as hydrate) plugging in the wellbore during deepwater drilling is not clear, so there are problems such as the overuse of hydrate inhibitors and the low utilization efficiency of inhibitors. Therefore, in [...] Read more.
At present, the formation mechanism of gas hydrate (hereinafter referred to as hydrate) plugging in the wellbore during deepwater drilling is not clear, so there are problems such as the overuse of hydrate inhibitors and the low utilization efficiency of inhibitors. Therefore, in view of the risk of hydrate formation and plugging under different working conditions during deepwater drilling, research was carried out on the wellbore hydrate formation area and wellbore hydrate deposition and plugging. Taking an atmospheric well in the South China Sea as an example, the wellbore annulus temperature field under different working conditions was combined with the hydrate formation phase curve to analyze the hydrate formation plugging risk under different working conditions during deepwater drilling, and the hydrate formation risk region of the wellbore under different working conditions was obtained. The effects of the drilling fluid circulation rate, injection temperature and drilling fluid viscosity in the wellbore annulus on the risk zone and subcooling of the wellbore hydrate formation were predicted. A deepwater drilling wellbore hydrate deposition plugging model was developed, based on which the dynamic deposition of the hydrate in the wellbore was predicted quantitatively. The results of the study showed that: (1) Increasing the circulation rate of drilling fluid, drilling fluid inlet temperature and drilling fluid viscosity during deepwater drilling can effectively reduce the hydrate formation region and subcooling, thus reducing the hydrate formation. (2) The risk of plugging by hydrate formation basically does not occur during normal drilling. (3) Under the condition of using seawater bentonite slurry drilling fluid, the safe operating time for stopping drilling is 20 h, and the safe operating time for shutting in and killing the well is 30 h. Full article
(This article belongs to the Special Issue Natural Gas Hydrate Production Technology and Rock Mechanics in Petroleum Engineering)
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17 pages, 5791 KiB  
Article
Pressure Relief-Type Overpressure Distribution Prediction Model Based on Seepage and Stress Coupling
by Gaolong Liao, Shusheng Guo, Chao Wang, Yuan Shen and Yanfang Gao
Processes 2023, 11(2), 480; https://0-doi-org.brum.beds.ac.uk/10.3390/pr11020480 - 05 Feb 2023
Cited by 1 | Viewed by 968
Abstract
At present, great progress has been made in the prediction of undercompaction and fluid expansion overpressure. However, in recent years, the field has frequently encountered pressure relief-type overpressure. Different from primary overpressure, such as undercompaction and fluid expansion, this type of overpressure belongs [...] Read more.
At present, great progress has been made in the prediction of undercompaction and fluid expansion overpressure. However, in recent years, the field has frequently encountered pressure relief-type overpressure. Different from primary overpressure, such as undercompaction and fluid expansion, this type of overpressure belongs to secondary overpressure, which has a certain concealment in response to seismic velocity and logging data. Based on this, a geological analysis model of pressure relief-type overpressure was established according to the seepage and stress coupling theory. The model can realize the prediction of pressure relief range and pressure distribution, which provides a new way to predict this kind of overpressure. The influence of the laws of porosity, permeability, and geological movement on pressure relief were analyzed. The research results provide a new method for the prediction of pressure relief-type overpressure and improving the basic guarantee of safe and efficient drilling. Full article
(This article belongs to the Special Issue Natural Gas Hydrate Production Technology and Rock Mechanics in Petroleum Engineering)
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21 pages, 7552 KiB  
Article
Effect of Annular Gas–Liquid Two-Phase Flow on Lateral Vibration of Drill String in Horizontal Drilling for Natural Gas Hydrate
by Baojin Wang, Liuci Wang, Xiangbo Meng and Fushen Ren
Processes 2023, 11(1), 54; https://0-doi-org.brum.beds.ac.uk/10.3390/pr11010054 - 26 Dec 2022
Cited by 2 | Viewed by 1320
Abstract
NGH (natural gas hydrate) is a sort of green energy with huge reserves. When drilling and exploiting NGH, the complex drilling environment will aggravate the vibration of the drill string, which will destroy the stability of the NGH reservoir and make it decompose [...] Read more.
NGH (natural gas hydrate) is a sort of green energy with huge reserves. When drilling and exploiting NGH, the complex drilling environment will aggravate the vibration of the drill string, which will destroy the stability of the NGH reservoir and make it decompose to produce a large amount of gas. Gas flows into the annular with the drilling fluid, filling the annular with a gas–liquid two-phase flow with a complex variation in the characteristic parameters of the pipe flow. The mixed gas–liquid annular flow will make the drill string vibration more complex and intense. In this study, the nonlinear mathematical model of the drill string lateral vibration is established by considering the influence of the internal and external fluids, gravity, and the bottom axial force on the lateral vibration of the drill string. The effect of the annular fluid velocity and gas content on the lateral vibration of the drill string was studied through experiments and numerical simulations. This study found that, with an increase in annular fluid velocity and gas content, the stability of the drill string is weakened, and the lateral vibration is intensified, so the effect of the annular fluid velocity on the lateral vibration of drill string is greater than that of the annular gas content. Full article
(This article belongs to the Special Issue Natural Gas Hydrate Production Technology and Rock Mechanics in Petroleum Engineering)
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15 pages, 15280 KiB  
Article
Study on the Solid Production Mechanism of the Fractured Granite Reservoirs-Example of YL Area in Qiongdongnan Basin
by Xiongdi Zuo, Tao Wang, Lanling Shi, Lei Lei, Jian Wu, Liangbin Dou and Tiantai Li
Processes 2022, 10(12), 2556; https://0-doi-org.brum.beds.ac.uk/10.3390/pr10122556 - 01 Dec 2022
Cited by 1 | Viewed by 939
Abstract
The granite buried hill gas reservoir in YL area of Qiongdongnan basin faces a serious problem of solid production, which seriously affects gas well production and reduces economic benefits; however, the solid production mechanism of fractured granite reservoirs is still unclear. In this [...] Read more.
The granite buried hill gas reservoir in YL area of Qiongdongnan basin faces a serious problem of solid production, which seriously affects gas well production and reduces economic benefits; however, the solid production mechanism of fractured granite reservoirs is still unclear. In this study, the reasons for solid production were revealed and the mechanism was clarified based on the analysis of geological and mechanical characteristics of the granite buried hill reservoir. The solid production of fractured granite reservoirs can be divided into three modes, those being shedding of fracture filling and solid particles on the fracture wall, shear slip failure along the fracture, and shear failure of granite matrix. Take the YL area in the Qiongdongnan Basin as an example, the solid production of fractured granite reservoirs is mainly based on shedding of fracture filling and solid particles on the fracture wall and shear slip failure along the fracture, the possibility of shear failure of granite matrix is less. In addition, the closer the wellbore, the greater the risk of shedding of fracture filling and solid particles on the fracture wall. The high-angle fractures have a greater risk of shear slip failure. In addition, the direction of the minimum horizontal principal stress is higher risk of solid production. The research provides the basis and foundation for safe and efficient development of fractured granite reservoirs and for later measure selection and optimization. Full article
(This article belongs to the Special Issue Natural Gas Hydrate Production Technology and Rock Mechanics in Petroleum Engineering)
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11 pages, 7278 KiB  
Article
Research and Practice of Risk Early Warning Technology for Lost Circulation with Drilling under the Conditions of Geological Engineering Information Fusion: The Example of the Yuanba Area
by Zhikun Liu, Rongtao Luo, Zhe Yang, Linjie Wang and Liupeng Wang
Processes 2022, 10(12), 2516; https://0-doi-org.brum.beds.ac.uk/10.3390/pr10122516 - 27 Nov 2022
Cited by 2 | Viewed by 976
Abstract
In the Yuanba area, many lost circulation accidents occur due to the complex geological structure, broken strata, and developed fractures, which seriously affect construction safety and drilling costs. Therefore, the Yuanba district is the focus of this paper. Firstly, a three-dimensional geomechanical model [...] Read more.
In the Yuanba area, many lost circulation accidents occur due to the complex geological structure, broken strata, and developed fractures, which seriously affect construction safety and drilling costs. Therefore, the Yuanba district is the focus of this paper. Firstly, a three-dimensional geomechanical model is established through multi-source information fusion to identify the main geological risk factors of lost circulation, according to the data on drilling and well logging in the operation area. Then a risk warning model and evaluation methods for loss circulation, based on geological engineering data fusion, are established, through which the characteristic parameters of various loss of circulation risks can be calculated in real time, parameters along the well trajectory can be extracted and compared, and thus, the risk of lost circulation is warned and analyzed in real time. The early warning of lost circulation risk can be achieved during drilling operations, which can improve the drilling efficiency and shorten the drilling cycle as a result. Full article
(This article belongs to the Special Issue Natural Gas Hydrate Production Technology and Rock Mechanics in Petroleum Engineering)
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15 pages, 5465 KiB  
Article
Influence of Water Saturation on Curtain Formation of Frozen Wall
by Hewan Li, Jian Liu, Laigui Wang and Tianjiao Ren
Processes 2022, 10(10), 2065; https://0-doi-org.brum.beds.ac.uk/10.3390/pr10102065 - 13 Oct 2022
Cited by 2 | Viewed by 866
Abstract
In the process of in situ mining of underground oil shale, it is necessary to build an underground frozen wall around the mining area to prevent the inflow of groundwater and prevent oil and gas leakage. However, the water saturation of the frozen [...] Read more.
In the process of in situ mining of underground oil shale, it is necessary to build an underground frozen wall around the mining area to prevent the inflow of groundwater and prevent oil and gas leakage. However, the water saturation of the frozen soil affects the formation of the freezing circle. In practical engineering, when building a frozen wall in soil under different water saturation conditions, the curtain is often not closed. It also affects the construction and operating costs of the entire project. In this paper, the methods of laboratory experiments and numerical simulation analysis are supplemented by the analysis of ordinary differential equations and partial differential equations. Aiming at the lowest cost, the temperature drop process and freezing time around the frozen well under different water saturation conditions are calculated and analyzed in detail. The formation law of the frozen wall curtain under different water saturation conditions is obtained. It provides a reference for the setting of the low-temperature loading time and the oil shale extraction range of frozen wells for different soils in practical engineering. Full article
(This article belongs to the Special Issue Natural Gas Hydrate Production Technology and Rock Mechanics in Petroleum Engineering)
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9 pages, 757 KiB  
Article
Research on the Influence of a Cuttings Bed on Drill String Friction Torque in Horizontal Well Sections
by Xiaoming Li, Yuyue Fan, Jiahua Li, Xinghua Su, Sheng Zhan, Gang Hu, Yiqing He and Ming Zhang
Processes 2022, 10(10), 2061; https://0-doi-org.brum.beds.ac.uk/10.3390/pr10102061 - 12 Oct 2022
Cited by 3 | Viewed by 1087
Abstract
Horizontal well drills are difficult to operate and require high borehole cleaning operations. The impact of cuttings accumulation on friction and torque cannot be ignored. In the process of horizontal well drilling, it is very easy to form a cuttings bed in the [...] Read more.
Horizontal well drills are difficult to operate and require high borehole cleaning operations. The impact of cuttings accumulation on friction and torque cannot be ignored. In the process of horizontal well drilling, it is very easy to form a cuttings bed in the highly inclined eccentric annulus. The formation of the cuttings bed will not only increase the friction torque but also have a greater impact on the annulus flow. Based on the application of gas drilling in horizontal wells, this paper uses laboratory experiments to study the influence of cuttings with different particle sizes and lithology on the friction coefficient between the drill string and the borehole wall of the horizontal well section. In addition, in view of the difficulty in the migration of cuttings in gas drilling horizontal wells and the formation of cuttings deposits, this paper carries out an experimental study on the effect of the cuttings bed on drill pipe coating height and cuttings bed thickness on friction coefficient. Experimental results show that the friction coefficient of gas drilling horizontal wells is about 0.44–0.58. When the coating height of the cuttings on the drill pipe exceeds a certain value (26 mm), the friction coefficient tends to be stable, but its value is as high as about 0.55. When the thickness of the accumulation of cuttings exceeds a certain value (10 mm), the subsidence hindering effect between the particles in the cuttings bed is weakened, so the friction coefficient of the casing section and the open hole section tends to be stable, about 0.53. Full article
(This article belongs to the Special Issue Natural Gas Hydrate Production Technology and Rock Mechanics in Petroleum Engineering)
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11 pages, 3355 KiB  
Article
Research on Erosion Wear of Slotted Screen Based on High Production Gas Field
by Fucheng Deng, Biao Yin, Yunchen Xiao, Gang Li and Chuanliang Yan
Processes 2022, 10(8), 1640; https://0-doi-org.brum.beds.ac.uk/10.3390/pr10081640 - 18 Aug 2022
Cited by 3 | Viewed by 1050
Abstract
Erosion wear is a common failure form of slotted screen in service. In this paper, based on CFD software and sand production data of a gas field in the Tarim Basin, the particle velocity and shear force at the slot of the flow [...] Read more.
Erosion wear is a common failure form of slotted screen in service. In this paper, based on CFD software and sand production data of a gas field in the Tarim Basin, the particle velocity and shear force at the slot of the flow field in the sieve tube were studied to determine the maximum area of erosion; at the same time, the velocity, viscosity, particle size and concentration of sand-carrying fluid were analyzed by orthogonal test, and the regression model of multi-factor maximum erosion rate was established. ① Through the analysis of the four factors on the degree of dependent variables, the order of the primary and secondary factors are: sand-carrying liquid flow rate, particle concentration, fluid viscosity, particle diameter, the effect of fluid viscosity and particle diameter on erosion rate is relatively small; ② According to the analysis of variance and range, the combination scheme of minimum erosion generation is obtained, and the calculation model of the erosion rate of the slotted screen is established. In order to reduce the erosion and abrasion in the actual oil and gas production process, the reasonable flow control and precise sand control method design and precision selection can be adopted; it provides a design basis for sand control and long-term effects of production in high-yield gas field. Full article
(This article belongs to the Special Issue Natural Gas Hydrate Production Technology and Rock Mechanics in Petroleum Engineering)
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18 pages, 19697 KiB  
Article
Analysis of Reservoir Stability during Natural Gas Hydrate Exploitation under Incline Seafloor
by Xiaolong Zhao, Zenglin Wang, Yizhong Zhao, Jiaqiang Zuo, Gang Chen, Peng Li, Wei Liang, Weixia Jia, Bing Wang and Xue Chen
Processes 2022, 10(8), 1614; https://0-doi-org.brum.beds.ac.uk/10.3390/pr10081614 - 15 Aug 2022
Viewed by 1207
Abstract
Natural gas hydrates (NGHs) have been recognized as a potential substitute for traditional fossil fuels. Mining NGH reservoirs can decrease the strength of the reservoirs, especially while improving production, and the double-well mining of NGHs also significantly reduces the strength of reservoirs. This [...] Read more.
Natural gas hydrates (NGHs) have been recognized as a potential substitute for traditional fossil fuels. Mining NGH reservoirs can decrease the strength of the reservoirs, especially while improving production, and the double-well mining of NGHs also significantly reduces the strength of reservoirs. This study develops a thermofluid-solid multifield coupling model for mining NGHs through depressurization while considering the NGH decomposition kinetics and physical properties of NGH reservoirs. The influence of the formation responses and burial conditions on the slope stability in the depressurization process of NGHs is analyzed by combining it with the finite-element strength-reduction method. Results show that the decomposition zones of NGHs are nonuniformly distributed in space and have an irregular prismatic shape. The pore pressure propagates from the wellbores to the surrounding areas, forming cylindrical high-pressure-drop zones. Plastic zones first appear in the decomposition zones of NGHs; then, they gradually spread to the slope shoulder and toe, eventually coalescing to form a plastic zone. The stability of submarine slopes declines with the increasing slope angle, reservoir thickness, and initial saturation of the reservoir, while it increases with the growing burial depth of the reservoir. The seabed settlement grows with the growing slope angle and initial saturation, and thickness of reservoirs, while it decreases with the rising burial depth of the reservoir. Full article
(This article belongs to the Special Issue Natural Gas Hydrate Production Technology and Rock Mechanics in Petroleum Engineering)
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13 pages, 6130 KiB  
Article
Study on Wellbore Stability Evaluation Method of New Drilled Well in Old Reservoir
by Shiyue Wang, Gaolong Liao, Zhenwei Zhang and Xiaoyun Wang
Processes 2022, 10(7), 1334; https://0-doi-org.brum.beds.ac.uk/10.3390/pr10071334 - 08 Jul 2022
Cited by 2 | Viewed by 1962
Abstract
The borehole wall stability of depleted reservoirs is a key problem that restricts the deeper potential exploitation of old oilfields. Based on these, according to the seepage and elastic mechanics theory of porous media, combined with laboratory rock mechanics experiments, the dynamic evaluation [...] Read more.
The borehole wall stability of depleted reservoirs is a key problem that restricts the deeper potential exploitation of old oilfields. Based on these, according to the seepage and elastic mechanics theory of porous media, combined with laboratory rock mechanics experiments, the dynamic evaluation model of geomechanical parameters of the old reservoir is established, and on this basis, the evaluation method of wellbore stability of new wells in the old reservoir is established, and the changing laws and influencing factors of the wellbore stability of the old reservoir are quantitatively evaluated. The research shows that reservoir pressure, reservoir porosity, effective stress coefficient, strength, in situ magnitude, and direction were all changed due to long-term exploitation; both collapse and fracture pressure decreased, the loss risk of drilling fluid was increased, and safe drilling azimuth was changed. The results can guide reasonable choices such as well position, track and mud density, and strengthening sealing while drilling in order to ensure wellbore stability effectively. Full article
(This article belongs to the Special Issue Natural Gas Hydrate Production Technology and Rock Mechanics in Petroleum Engineering)
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14 pages, 9055 KiB  
Article
Research on Wellbore Instability of Shale Formation in Extremely Complex Geo-Mechanical Environment
by Junliang Yuan, Kai Zhao and Yongcun Feng
Processes 2022, 10(6), 1060; https://0-doi-org.brum.beds.ac.uk/10.3390/pr10061060 - 25 May 2022
Cited by 1 | Viewed by 1809
Abstract
Borehole instability problems are commonly encountered while drilling highly deviated and horizontal shale gas wells within the shale formations associated with high-dip bedding planes. An integrated rock mechanical study is described in this paper to evaluate the risk of the borehole instability problems [...] Read more.
Borehole instability problems are commonly encountered while drilling highly deviated and horizontal shale gas wells within the shale formations associated with high-dip bedding planes. An integrated rock mechanical study is described in this paper to evaluate the risk of the borehole instability problems in this area. First, a set of uniaxial compressive tests are carried out to measure the strength of the bedding shales on cores with different angles between the load direction and the bedding planes. A critical strength criterion is then proposed based on the test results. Next, the stress state of the borehole with arbitrary inclination and azimuth is determined through coordinate transformations. Finally, through combining the strength criterion and the stress state of the borehole, the risk of borehole instability is investigated for deviated and horizontal wells in shale formations with different bedding dips (0–90°) and dip directions (45° and 90° to the direction of minimum horizontal stress σh). The results show the dependence of borehole instability on the orientation of bedding planes of the formation as well as inclination and azimuth of the well. The most desirable borehole trajectory from the viewpoint of borehole stability is at the direction normal to the bedding planes. For a horizontal well specifically, if the bedding direction is perpendicular to the direction of σh, the risk of instability is relatively high for most drilling directions except drilling along the dip direction of the bedding planes. However, if there is a moderate acute angle (e.g., 45°) between the dip direction and the direction of σh, the risk of instability is relatively low for most drilling directions unless drilling along the direction of σh. Full article
(This article belongs to the Special Issue Natural Gas Hydrate Production Technology and Rock Mechanics in Petroleum Engineering)
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19 pages, 3383 KiB  
Article
A New Method of Quantitatively Evaluating Fracability of Tight Sandstone Reservoirs Using Geomechanics Characteristics and In Situ Stress Field
by Liangbin Dou, Xiongdi Zuo, Le Qu, Yingjian Xiao, Gang Bi, Rui Wang and Ming Zhang
Processes 2022, 10(5), 1040; https://0-doi-org.brum.beds.ac.uk/10.3390/pr10051040 - 23 May 2022
Cited by 3 | Viewed by 1515
Abstract
This paper studied the fracability of tight sandstone reservoirs by means of incorporating geomechanics properties and surrounding in situ stresses into a new model. The new fracability evaluation model consists of variables such as brittleness index, critical strain energy release rate index, horizontal [...] Read more.
This paper studied the fracability of tight sandstone reservoirs by means of incorporating geomechanics properties and surrounding in situ stresses into a new model. The new fracability evaluation model consists of variables such as brittleness index, critical strain energy release rate index, horizontal stress difference, and minimum horizontal principal stress gradient. The probability of interconnection of a complex fracture network was quantitatively studied by the brittleness index and horizontal principal stress difference index. The probability of obtaining a large stimulated reservoir volume was evaluated by the critical strain energy release rate index and minimum horizontal principal stress gradient which also quantifies conductivity. This model is more capable of evaluating fracability, i.e., it agrees better with the history of production with a high precision and had correlation coefficients (R2) of 0.970 and 0.910 with liquid production of post-fracturing well testing and the average production of six months of post-fracturing, respectively. It is convenient that all model inputs were obtained by means of loggings. Using this model, tight sandstone reservoirs were classified into three groups according to fracability: Frac ≥ 0.3 MPa−1·m for Type-I, 0.22 MPa−1·m ≤ Frac < 0.3 MPa−1·m for Type-II, and Frac < 0.22 MPa−1·m for Type-III. Full article
(This article belongs to the Special Issue Natural Gas Hydrate Production Technology and Rock Mechanics in Petroleum Engineering)
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16 pages, 3404 KiB  
Article
Transient Pressure and Temperature Analysis of a Deepwater Gas Well during a Blowout Test
by Haiquan Zhong, Chuangen Zheng, Miao Li, Tong Liu, Yufa He and Zihan Li
Processes 2022, 10(5), 846; https://0-doi-org.brum.beds.ac.uk/10.3390/pr10050846 - 25 Apr 2022
Cited by 5 | Viewed by 1762
Abstract
On one hand, a blowout test can clean the bottom of the well, and on the other, it can learn the productivity of the well, which is important work before putting the well into production and also the main basis for production allocation [...] Read more.
On one hand, a blowout test can clean the bottom of the well, and on the other, it can learn the productivity of the well, which is important work before putting the well into production and also the main basis for production allocation of the well. The accurate prediction of the blowout test process provides a theoretical basis for the design of a reasonable blowout test system and the determination of well cleaning time. During deepwater blowout tests, gas and liquid flows are unsteady in pipes, and flow parameters change over time. At present, accurately predicting changes in fluid temperature, pressure, liquid holdup, and other parameters in a wellbore during an actual blowout process using the commonly used steady-state prediction methods is difficult, and determining whether a test scheme is reasonable is impossible. Therefore, based on the conservation of mass, momentum, and energy during the blowout test process, in this study, formation, wellbore, and nozzle flows were coupled for the first time, and a time and space of unsteady pressure drop and a heat transfer differential equation system was established; furthermore, using the Newton–Raphson method, the equations were solved. Finally, the simulation of the transient flow of the blowout test was completed. Considering a measured deepwater gas well A as an example, the blowout test process was simulated, and the variations in the wellbore flow parameters were analyzed. Comparing the simulation result with the test data, we concluded the following. (1) During the blowout process, the wellbore temperature gradually increased; pressure at the bottom of the wellbore decreased; and pressure at the wellhead increased; and (2) the established model agreed well with the actual production data, and the average error of the wellhead pressure and temperature was less than 5%. Considering the high production capacity of deepwater gas wells, the use of large-sized tubing and nozzles to spray is recommended, which can improve the speed of clearing wells and prevent the formation of hydrate. Full article
(This article belongs to the Special Issue Natural Gas Hydrate Production Technology and Rock Mechanics in Petroleum Engineering)
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14 pages, 9525 KiB  
Article
Numerical Simulation of Influencing Factors of Hydraulic Fracture Network Development in Reservoirs with Pre-Existing Fractures
by Kai Zhao, Runsen Li, Haoran Lei, Wei Gao, Zhenwei Zhang, Xiaoyun Wang and Le Qu
Processes 2022, 10(4), 773; https://0-doi-org.brum.beds.ac.uk/10.3390/pr10040773 - 15 Apr 2022
Cited by 5 | Viewed by 1532
Abstract
The intersection behavior of hydraulic fractures and single natural fractures has been studied in detail; however, in fractured reservoirs, natural fractures are numerous and interlaced and the intersection of hydraulic fractures and multiple natural fractures occurs during the fracturing process. This intersection behavior [...] Read more.
The intersection behavior of hydraulic fractures and single natural fractures has been studied in detail; however, in fractured reservoirs, natural fractures are numerous and interlaced and the intersection of hydraulic fractures and multiple natural fractures occurs during the fracturing process. This intersection behavior is more complex and there is a lack of research on this topic at present. In this study, a numerical simulation model of the interaction between hydraulic fractures and a series of natural fractures was established, the main factors that affect the formation scale of a fracture network during the hydraulic fracturing of a fractured reservoir were studied using the numerical simulation method, and the parameters were also studied. The results showed that the natural fracture trend, in situ stress difference, and injection flow rate have an impact on the scale of a fracture network. The larger the in situ stress difference, the smaller the scale of the fracture network, which gradually changes from multiple clusters of fractures to single fractures. The larger the injection flow rate, the larger the scale of the fracture network. In the uniform stress field, the direction of a natural fracture is closer to the direction of principal stress, so the lower the fracture extension pressure, the smaller the scale of the network. On the contrary, the farther away from the principal stress direction, the lower the fracture extension pressure and the higher the extension pressure, the larger the scale of the fracture network. Full article
(This article belongs to the Special Issue Natural Gas Hydrate Production Technology and Rock Mechanics in Petroleum Engineering)
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Review

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32 pages, 8682 KiB  
Review
A Review on Application of Acoustic Emission in Coal—Analysis Based on CiteSpace Knowledge Network
by Shankun Zhao, Qian Chao, Liu Yang, Kai Qin and Jianping Zuo
Processes 2022, 10(11), 2397; https://0-doi-org.brum.beds.ac.uk/10.3390/pr10112397 - 14 Nov 2022
Cited by 3 | Viewed by 1409
Abstract
Based on CiteSpace software, this paper reviews and analyzes the application articles of acoustic emission in coal from 2010 to 2020. In this paper, CiteSpace software visualizes 453 articles collected in the Web of Science core database. The cooperation networks between different countries, [...] Read more.
Based on CiteSpace software, this paper reviews and analyzes the application articles of acoustic emission in coal from 2010 to 2020. In this paper, CiteSpace software visualizes 453 articles collected in the Web of Science core database. The cooperation networks between different countries, institutions, and authors are used to determine the connection of knowledge in papers. The keyword co-occurrence, keyword co-occurrence time zone map, and keyword clustering are used to determine the hot topics in the field. The cited collaborative network analysis reveals the important literature and the contribution of prominent authors in this area. In the future, for the research of acoustic emission in coal mining, compression tests will still be the main test methods. In terms of time domain parameters of acoustic emission, the application of ring counting, energy, waveform, and signal strength are very mature. The principal problem of acoustic emission location operation will become a focus in the future. The most widely used patterns in the determination of ruptures are the signal intensity fractal dimension, the acoustic emission number, and the b-value. In practical engineering problems, there is little research on the deformation activity law of steeply inclined coal seams and surrounding rock. The mining of steeply inclined coal seams is still a difficult problem. There are immature technologies in coal mining, rockburst early warning, and coal and gas outburst. In terms of the intellectualization and accuracy based on experience, there is room for improvement in the future. Scholars will continue a deeper exploration on the application of the numerical simulation. Full article
(This article belongs to the Special Issue Natural Gas Hydrate Production Technology and Rock Mechanics in Petroleum Engineering)
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