bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Weak Bedding Planes on Wellbore Stability for Shale Gas Wells
Authors: Li Yufei , Fu Yongqiang , Tang Geng , She Chaoyi , Guo Jianhua , Zhang Jiyin 
Published: July 2012

Abstract
For shale gas reservoirs with the characteristics of bedding planes developed, hydrated easily and strong anisotropy of the mechanical properties, this paper couples conventional logging, image logging and real-time drilling data with laboratory rock mechanical and in-site stress tests, and establishes a wellbore stability analysis model for shale reservoirs. This analysis covers weak bedding planes, mechanical anisotropy and time effects. Besides, the effect of these above factors on the wellbore stability for horizontal wells in shale reservoirs is studied, and wellbore collapse mechanism for the shale reservoirs in Sichuan Basin is also analyzed.
Based on the established wellbore stability analysis model, this paper analyses the well W-H1, the analysis results are in good agreement with real drilling data.
Study and field application results indicate that weak bedding plane effects mainly affect wellbore collapse of horizontal wells for shale reservoirs, which differs from conventional sand reservoirs and carbonate reservoirs, even for the vertical wells in the shale reservoirs.
The study provides a theoretical basis for W-H1 well drilling and completion design, such as drilling fluid design, wellbore structure optimization and completion method optimization, etc.
Investigation on the Differential Pressure Leakage of Thief Formation
Authors: Shi Lin , Jiang Hongwei , Guo Qingfeng , Song Peng 
Published: July 2012

Abstract
Leakage mechanism is the basis to study the formation leakage phenomenon and quantitatively analyze the characteristics of the leakage formation. The leakage phenomenon is divided into differential pressure leakage and fractured leakage in this paper. By simulating the U-tube, we analyze the leakage mechanism of different lithology. The calculation formulas of leakage volume and leakage velocity on differential pressure leakage are brought forward by making use of water injection model.
The analysis applied to the leakage of Sinkiang Baiquan-1 Well, Laoyemiao region of Eastern Hebei oilfield and TABNAK gas field of Iran. Based on the investigation, it is clearly incorrect that the leakage of Sinkiang Baiquan-1 Well is attributed to fractured leakage or rupture leakage, but should be considered as differential pressure leakage. The lost circulation in Eastern Hebei oilfield is mainly caused by the permeable leakage based on declined pressure. Because the connectivity and porous fracture development of carbonate formation in TABNAK gas field of Iran are good, the serious leakage happened in the formation above sea when there were positive pressure between the mud and the formation.
Investigation results show that in fracture formation with good permeability or in other thief formation which has fracture- cavity, the leakage type is mostly differential pressure leakage and rarely fractured leakage. So when analyzing the safe drilling density window, differential pressure leakage should be regarded as the main object to prevent.
It will be helpful to further analyze the leakage mechanism, and essential to formulate the leakage prevention and plugging program that the leakage is divided into differential pressure leakage and fractured leakage and the concept of differential pressure leakage is put forward.
Application of Multilateral Wells in Burial-hill Migmatitic Granite Formation
Authors: Yu Lei , Yu Chen , Shang Xianfei , Chen Zhengang , Wu Sheng , Zhao Yun , Liu Yanqiang 
Published: July 2012

Abstract
In view of low possibility across fractures, low controlled reserve for a single well, fast production decline, poor development performance for conventional horizontal well and directional well in the liaohe buried-hill migmatitic granite reservoir with characteristics of deep buried-depth, hard rock formation, fractured low porous and permeability, optimization deployment of variety of multilateral wells increases effective footage in pay zone and achieves better development performance by the spatial distribution of several lateral boreholes in a single well. Many challenges such as casing cutting, suspended sidetrack drilling in open hole and retrieving whipstock in this formation are solved, and that delivers records of window opening at the formation in scale of hardness 8, deepest window depth of 3523m. As of today, 40 multilateral wells have been completed with effect improved 3 times as offset vertical wells, 1.5 times as horizontal well. It becomes an approach to develop such reservoirs due to huge economical benefits.
Adding Sand Fracture Stimulation Technology in Tarim Ultra-deep and High Stress Sandstone Gas Reservoir
Authors: Zhang Fuxiang , Che Mingguang , Yang Xiangtong , Zhou Fujian , Yuan Xuefang 
Published: July 2012

Abstract
Hydraulic fracturing is a fissured tight gas productive completion technique in KuqaHPHT fieldin Western China, the gas zone is buried in deeper earth's crust in thatsand fracruring has been fored to deal with hotter tempetures, higher pressures and higherstess. During past decades, the fracturing stimulations underulta-deep high tempeture high pressure and high stess have been performed for higher yieldsin Kuqagasfield.
This paper provides a brief developed histotyof Kuqa and the characteristics of formations, such as Jura AH sandstones, Paleogene SWY sandstones and Cretaceous BSJQK sandstones.In major, this paper introduces the techniques and experiments necessary for the treatment of adding sand fracture stimulation, including rock mechanical laborary tests and stress porfiles, weighted fluids and their performances, resin coated proppanttests, and minifracdiagnotics that are performed to help designer an effective approach for fissured high stress hydraulic fracturing.In addition,frac string,140MPa fracturing equipment and 140MPa well head, which are the countermeasures of high treatment pressure, are discussed in this paper. Fianl, twofield examples of proppant fracturing treatments are included, andthe deepest fracturing reservoir is neighborto 7000m, thecontinuoushigh surface pressure is over 120MPa.
The production of fracturing wells is excited in the fissured high stress tight gasfieldof Kuqa. Many components of this paper may be helpful for those preparing for a HPHT high stress treatment.
The Problems and Solutions in The Drilling at The Right Bank of Amu Darya in Turkmenistan
Authors: Liu Bingshan , Wang Xi , Li Wanjun , Zhang Shaoyun , Dong Jianhui , Yang Yuping 
Published: July 2012

Abstract
Arum River Basin is a large scale sedimentary basin lying in the southeast of Tejen platform. Amu Darya right bank is situtated between Amu Darya and the border of Turkmenistan and Uzbekistan. There are several difficult problems in the drilling of this area: overpressured gas reservoir, shallow secondary gas pool with ultra-high pressure, high pressured saltwater layer and high tempreture of bottom hole and so on. So the success rate of the more than 200 wells drilled by the oil companies of Former Soviet Union and Turkmenistan is less than 30%.
We solved these problems by optimizing borehole structure, optimizing drilling fluid system and strenthenning the system of well control etc. Up to 2010, more than 50 wells were drilled successfully in this area. The success rate is 100%. It is a great break in the drilling of Amu Darya right bank area.
Dual-Factor Method for Calculating Weight Distribution in Reaming While Drilling
Authors: Ma Rutao , Ji Youzhe , Wang Hui , Han Fei 
Published: July 2012

Abstract
Based on lab tests and theoretical analysis, a dual-factor method for calculating weight distribution between the pilot bit and underremer is presented.
The novel method yields much more precise results than empirical values, thus can be used to determine weight distribution factor for an underremer-bit assembly.
A weight distribution factor f was used in this paper to represent the bit-underreamer interaction with the formation and reacts to weight inputted from the surface. As to the factor f, traditional calculation method only focuses on geometrical structure of the pilot and main hole, results arising therefrom are too rough to be used. Dual-factor method avoids such drawbacks by introducing two factors. A factor k termed sharpness represents drilling tools’ ability to penetrate the formation, and the other factor σ termed compressive stress represents formation strength. The two factors are defined by lab tests. Influence on the distribution of each factor was analyzed, and results show that weight distributed on the underreamer will increase as the formation stress σ increased, and decrease as the underreamer sharpness k decreased.
Well known in the reaming while drilling process is the importance of proper matching for the bit and underreamer. Improper drilling assembly will lead to sever vibration and decreased ROP for the drilling system. An underreamer should not be designed and employed as an independent tool. Dual-factor method provides a good reference for matching underreamer-bit assembly. Also, applying this method, design process for an underreamer can be optimized, and reaming while drilling operating will become more stable.
Research on Treatment of Abandoned Water-based Drilling Fluid by Low Pressure Distillation Process
Authors: Wang Youhua , Shu Fuchang , Xiang Xingjin , Zhang Yan , Luo Gang , Huang Mingzhao 
Published: July 2012

Abstract
Waste water-based drilling fluids have some characteristics, such as complex chemical composition, colloidal stability, high COD (Chemical Oxygen Demand), low BOD (Biochemical Oxygen Demand)/COD ratio and poor chemical and biological degradation. As a result, such treatments as biochemical, chemical oxidation or membrane separation process has the deficiency of poor adaptability, poor treatment efficiency and high running costs. This paper has studied the treatment technology of low pressure distillation process for waste water-based drilling fluids.
This technology has been applied in four wells of CPOE5 platforms in Dagang oilfield. The field application results have shown that this technology used to treat waste water-based drilling fluid can efficiently reduce COD, especially has good adaptability to different kinds of drilling fluids.
The treatment technology studied in this paper can treat wastewater's COD to lower than 150mg/L. The disposed waste-water can reach the class II water quality requirements of China national standards (integrated wastewater discharge standard, GB8978-1996) and can be directly discharged into sea.
This technology can control the influence and harm of waste drilling fluid on marine environment and meet the requirements of offshore environmental protection.
Under-balanced Drilling Technology Applied in China's CBM Exploitation
Authors: Xia Yan , Shen Ruichen , Yuan Guangjie , Zheng Lihui , Tian Maofa , Li Jingcuil 
Published: July 2012

Abstract
For the characteristics of low pressure and low permeability of coal reservoir in China, conventional drilling may damage reservoirs and reduce the production of CBM. In order to find efficient drilling technology used for CBM development, three kinds of under-balanced drilling technologies—gas drilling, aerated liquid drilling and circulated micro-bubble drilling have been used for CBM development. Considering the different characteristics of three kinds of under-balanced drilling technologies, firstly, by analyzing the use of gas drilling, characteristic of coal seam and technical measures for gas drilling, besides that, considering the characteristics of CBM and the state of drilling technology in China, the feasibility of gas drilling technology used in China's CBM development. Secondly, the research result and field application of aerated liquid and circulated micro-bubble under-balanced drilling technique are introduced. In the end, the importance of under-balanced drilling for reservoir protection and layer-loss prevention is stated.
Research and Application of Horizontal Drilling for CBM
Authors: Shen Ruichen , Qiao Lei , Fu Li , Yang Henglin , Shi Wen 
Published: July 2012

Abstract
This paper elaborates on development of horizontal drilling technology for coalbed methane (CBM) in China, from the perspective of optimization of well structure, well path control, and underbalanced drilling. Based on the research and application results of horizontal drilling for CBM, a few advices are presented.
Since the coal bed in China is characterized with low pressure, low permeability, low saturation and strong anisotropy, horizontal drilling is becoming a favorable choice in CBM development. The horizontal drilling technique and remote intersection technique have been applied successfully in CBM development in Qinshui Basin, proving good results in enhancing drilling efficiency, protecting the reservoir, as well as lowering the cost of drilling.
With the rapid development of CBM industry in China, researches on horizontal drilling, U-shaped wells, and multibranched wells have been carried out, covering new techniques research, software development and equipments invention. The horizontal drilling techniques that are suitable for China CBM development have formed, which drives the CBM industry to a future of low risks, low investment, high efficiency and high yield.
One New Needle Technology of Remote Intersection between Two Wells and Application in Chinese Coalbed Methane Basin
Authors: Tian Zhonglan , Shen Ruichen , Qiao Lei 
Published: July 2012

Abstract
On the basis of coal-bed methane particularity in China, the pressure, penetration and water-bearing are low. Generally, an extra straight well is needed for the coal-bed methane horizontal wells. And the straight well is connected to the horizontal wells for the entry of rod pump etc to drain water and collect gas. For the connection spot of the vertical well and horizontal well is less than 0.5m in diameter, the connection goal can not be achieved by conventional wellpath measurement. Based on the features of horizontal well, a suit of remote needle technique and relevant equipment is invented, which is used to guide the intersection between horizontal wells and the vertical well. The theoretical principle is rotating magnetic field orientation. By processing the real-time collection data of rotating magnetic field, the distance and angular deviation of drilling direction can be calculated to locate the drill bit and the vertical cavity, and connect the horizontal well and vertical well.
In this paper, wellpath measurement and controlling model, method of remote needle technique, and theory of needle equipment were elaborated. This technique has been applied successfully to six horizontal wells in Chinese coal-bed methane basin, such as Ordos basin. All intersections were finshed once only. In the field application, 60m distance away from the cavity can be precisely located for leading connection, the signal of magnetic field is distinct. By the improvement of the model, the system possessees the capability of measuring well deflection to guide the nitersection in 3D. The success of applying needle technique to Ordos basin demonstrates that the established measurement model of needle can be used for the intersection of coal-bed methane horizontal wells, and positioning accuracy of needle equipment satisfy the field demand.
The Horizontal Massive Multistage Fracturing Meet the Changling Tight Gas Field Development Strategy
Authors: Wang Feng , Zhang Yingan , Zi Hongbo , Pang Qiqiang , Liu Guangyu , Zhu ZhaoPeng , Li Biansheng , Duan Yongwei 
Published: July 2012

Abstract
The deep tight gas reservoir in southern Songliao basin has features of deep burial, dense lithology, poor physical property, high in-situ stress and no natural deliverability. Early development practice certificated that neither horizontal well nor conventional vertical fracturing can achieve promising stable production. This paper presents the successful case history in which the horizontal massive multistage fracturing techniques are developed. This includes optimizing horizontal section, optimizing the horizontal well completion and fracturing design, the slim open-hole packer sliding sleeve multistage fracturing technique and the large scale traversing fracturing technology. Also the deep well fracturing operation safety and surface security technique are discussed in the paper. At present 9 wells 100 stages has been operated, and achieved the target of most 15 stages and maximum 1451m3 proppants in a single well. The stable production rate of the fractured horizontal well was 5 times more than the around vertical well. This technology can fracture more stages, shorten operation time, lessen formation damage and reduce friction drag. So it maximizes the reservoir stimulation volume, which provides technical support for large-scale development of the tight gas sandstone reservoir in Changling gas field.
Trapping Damage Analysis of Water Locking/Aqueous Phase of Tight Sandstone Gas Reservoir in Ke Keya Structure
Authors: Lu Hongjie , Guo Jianshe , Wang Yongkang , Yang Min , Nan Wenze 
Published: July 2012

Abstract
In order to reduce water locking/aqueous phase trapping damage caused by drilling completion and fracturing acidizing operation of tight sandstone gas reservoir in Ke Keya structure, and improve infiltrating conditions of reservoir gas phase to achieve business development effect, in view of reservoir characteristics of tight sandstone gas reservoir, the water locking/aqueous phase trapping damage mechanism and effect factors are analyzed. By means of natural core of the tight sandstone gas reservoir in Ke Keya structure, the method for using methanol hybrid simulated formation water saturation has been established different core water saturation, and studied the effect of time and depth of capillary imbibitions formation water and other factors on reservoir, permeability and water locking/aqueous phase trapping damage, as well as the effect of water saturation variation on reservoir permeability and water locking/water phase trapping index in different methanol concentration water saturation. Two experimental methods for adopting three groups of different permeability, porosity cores has been made separately damage evaluation experiments, the results obtained are consistent. The experimental results show that the reservoir water saturation is less than 20%, and has the strongest effect of water phase trapping. With the reservoir water saturation increasing, aqueous phase trapping effect gradually decreases while water locking effect gradually increases, gas phase permeability is significantly decreased, and the water saturation ranging from 0 to 40% greatly drops. When the reservoir water saturation is more than 60% of the critical value, the water locking damage is increased, and the permeability of matrix becomes very small, and even loss of percolation capacity. Experimental results have guiding significance for controlling reasonably water saturation of tight sandstone gas reservoirs in Ke Keya structure, and provides reference for inhibiting water locking/aqueous trapping damage in low permeability gas reservoirs.
An Integrated Approach to Improve Drilling Performance and Save Cost in North Azadegan Field
Authors: Rong Li , Chengjin Yu , Yunzhang Zhou , Zhiping Li 
Published: July 2012

Abstract
Although some wells from other exploration and development projects in onshore Iran have been finished before, there is a big challenge for North Azadegan field to drill 58 wells in less than 3 years, with more than 8 upgraded 2000HP rigs in the marshy area under the economic sanction surrounding according to strict requirements of Buy-Back development contract. Moreover, operation area with average 2m water depth, about 2000m directional length section accompanied with narrow mud density window, violently fluctuations in rock strength and complete losses during cementing have also contributed to increased NPT with associated high costs in N.Azadegan field.
This paper will focus on main drilling problems and integrated technique, as well as the experience and lessons learned in implementing the Iran's development project. Specific key tactics discussed include: maximum utilization of Iranian contents, cluster well pad and auto-move rig system, bit selection and modified drillable float& shoes accessories, losses and overflow prevention measures, surface back pressure performed immediately after cement placement in a few time, a clear process for capturing the best practices and lessons learned.
An integrated approach was formed to decrease single well duration with less money ahead of schedule which was fixed 120d in Buy-Back contract. On the first 10 wells, average drilling performance was improved 57% and saved millions of U.S dollars with key solutions to overcome drilling challenges.
Complicated Drilling in Extremely Thick Ultra-Deep Salt Formation in Tarim-Case of KeShen Well 7
Authors: Wenhua An , Xueqing Ten , Da Yin , Hongjun Liang , Yan Ye , Chunsheng Wang , YingLin Jia , Xiaochun Li 
Published: July 2012

Abstract
The Kuga thrust belt in Tarim Basin is supposed to be one of the areas which concentrated difficult and problems for drilling on land of China. Reservoirs here are deeply buried and with extremely thick salt bed, which is comprised of salt rock, salt lime rock and soft mudstone, micro-cracked sandstone between salts and high pressured saltwater layer. Drilling in ultra-deep salt layer has become a extremely difficult work, especially when the depth is over 6500 meters and the temperature is over 180 Celsius.
According to the difficult of drilling in extremely thick salt layer in Tarim, a safe density design plate has been created, casing program has been optimized and a new type drilling fluid with high quality has been imported after the creep behavior of salt formation has been analyzed. In this paper, many matched drilling technologies used in KeShen Well 7 have been introduced. The designed depth of KeShen 7 is 8100 meters, the salt layer buried at 7211-7944m, the maximum pressure coefficient of saltwater layer between salts is 2.42 g/cm3, maximum mud density is 2.55 g/cm3 and the maximum bottom hole temperature is 186 Celsius. To improve the ability of dealing with complex geological condition, an unusual casing program has been developed, and a high-density oil-based drilling fluid has been applied. Precipitation Isolation Plugging Technology had been innovatively applied when the loss circulation and blowout happened simultaneously in the high pressure saltwater layer. As a result, the thick salt layer had been drilled through successfully at 7944 meters and the 81/8™ liner had been tripped in 7945 meters smoothly.
All these new technologies will bring a complete set of demonstration drilling engineering technology for foreland thrust belt engineering technology research.