bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of a Software System for Drilling Optimization using Surface and Downhole Drilling Data Modeling a Human Process for Drilling Optimization
Authors: Hanley Chris , Stuart Simon , Bass Chad , Garcia Alexis
Published: July 2012

Software systems are developed with the intent of providing methods to perform specific business tasks. However, in actual use cases, additional human processes or supplemental software are often required to complete the business process. In ideal cases, the software would guide the user through the entire business process and significantly aid in the required decision making or analysis to complete the process.

This paper will present the development of a new drilling optimization software system ergonomically modeled on key business and analytical processes. These key processes have been organically developed over a number of years for a commercial drilling optimization service using data from downhole drilling dynamics recorders. A multi-disciplinary project team including business unit managers, project coordinators, data analysts, software architects and developers was assembled. The project team designed the new system to ensure it would fit the human processes that had historically been used to support the commercial service.

The new system models all of the key business processes associated with the commercial drilling optimization service. These processes include job setup, mobilization of tools, assignment of field personnel to the job, acquisition of all required data in the field, and reporting tools for field personnel.

The system also provides the user with an intuitive suite of data analysis and drilling optimization techniques. These include automated processes for handling, merging, analyzing, and presenting the surface drilling parameters and recorded downhole drilling dynamics data. Additionally, the user is provided with recommended data analysis and optimization routines from the system based on data entered throughout the business processes from job setup to field operations and based on trends identified in the surface parameters and recorded downhole drilling dynamics data imported into the system.

Case studies demonstrating the value-added to the users of the new system will be presented.
Second Generation Interval Control Valve (ICV) Enhances Operational Efficiency and Inflow Performance in Intelligent Completions
Authors: Rahman Jameel , Allen Clifford , Bhat Gireesh
Published: July 2012

Intelligent completions were introduced over a decade ago to address completions and reservoir management challenges arising from highly-deviated, extended-reach, multi-targeted, or multilateral wells. Recent advances in exploration and drilling technology are enabling the oil and gas industry to target reservoirs with stratigraphic and depositional complexities in deepwater, subsalt, arctic, and other extreme environments, resulting in the need to develop a new generation of intelligent completion tools. These reservoirs also may be characterized by HPHT, extreme HPHT, or ultra-HPHT environments with multiple components contributing to the uncertainty of recovery.

This paper describes how the requirements of current and future reservoir environments and a decade of operational experience have shaped the functional design and qualification of a new-generation Interval Control Valve (ICV) for intelligent completions. The new-generation ICV has higher pressure and temperature tolerances to cater to the new harsher environments while simplifying its operating mechanism and improving inflow performance and debris tolerance. The qualification program included metal-to-metal seal qualification, life-cycle testing, API 14A SCSSV class II- sand slurry based tests, flow coefficient (Cv) test, seal stack qualification, and erosion testing. Descriptions of each qualification test, acceptance criteria and test results that demonstrate the capability of the new generation of ICV to perform in severe service conditions are presented in this paper.

Field applications of the second generation valve have shown additional operational benefits not even considered during the design. Technologies such as real time ICV position feedback have further aided in maximizing efficiency by enabling the use of downhole or surface positioning. Surface positioning devices can choke flow by varying ICV positions. The use of surface positioning enhances reliability by reducing the number of tools required downhole. Finally the paper outlines the operational limits of the current design and discusses the design enhancements planned for the next generation ICV.
Effect of Liquid Invasion and Capillary Pressure on Wireline Formation Tester Measurements in Tight Gas Reservoirs
Authors: Andrews Joshua Thomas , Bahrami Hassan , Rezaee Reza , Mehmood Sultan , Salemi Hossein , Pourabed HamidReza
Published: July 2012

Wireline formation testing and measurement of true formation pressure can provide essential knowledge about the reservoir dynamic characteristics. In tight formations, a reliable determination of pressure and mobility gradients is challenging because of the tight nature of formation rock. Due to the very low reservoir permeability, the mud cake across wellbore is often ineffective in preventing filtrate invasion, thus causing the measured pressure to be higher than actual formation pressure as a result of supercharging effect. Wireline formation testing measurements are also influenced by the effects of filtrate invasion and capillary pressure, as the measured pressure is pressure of drilling fluid filtrate, the continuous phase present in the invaded region around wellbore. As a result, the measured pressure might be different to true formation pressure. This effect is more noticeable in tight gas reservoirs due to capillary pressure effect.

This paper looks into estimation of true formation pressure and evaluates the effect of filtrate invasion damage and supercharging on wireline formation tester measurements in tight gas reservoirs. Numerical simulation approach is used to build the reservoir model based on data acquired from a tight gas reservoir. The model undergoes water injection followed by gas production from different testing points along the wellbore, and the corresponding pressure gradients are plotted to check for pressure matching with that of the formation fluid in the virgin region. The results indicate the significant effects of supercharging, reservoir characteristics, capillary pressure and liquid invasion damage on wireline formation pressure measurements in tight gas reservoirs.
Challenges in Deep Shale Gas Drilling: A Case Study in Sichuan Basin
Authors: Li Gao , Liu Houbin , Meng Yingfeng , Leng Xueshuang , Jia Hongjun , Li Hongtao , Hu Jinke
Published: July 2012

As an unconventional gas resource, shale gas has been developed mostly in shallow reservoirs which are mainly buried in depth form 76 m to 2439 m in the world. However, the deep shale gas is drawing more attention as time goes by. In this paper, deep shale gas in Sichuan Basin is studied as an example where the shale gas reservoirs are mostly buried deep in depth from 2300 m to 4500 m. Because the shale gas in Sichuan Basin is buried deep with high formation pressure and the formation conditions are complex, there are many problems that will be encountered during drilling, such as wellbore instability, serious formation damage by high drilling fluid pressure, and low drilling efficiency, etc. In this paper, shale gas reservoir in Long maxi Group of Sichuan Basin is studied as a case for deep shale gas drilling. Basic characteristics of strata profile, lithological characteristics, formation fluids and formation pressure are analyzed combined with previous drilling data. Based on this, wellbore stability and formation damage are evaluated. The study indicates that in a relatively high borehole stress condition with a Mechanic-Chemical coupling, shale with lamellar, brittle and high clay content has a high collapse stress, and borehole trajectory design and drilling fluid performance are crucial to wellbore stabilization. Meanwhile, in deep shale drilling of this area, liquid phase will invade into bedding fissures and tectonic fractures to form a liquid phase trap between the fractures and matrix, so that the shale formation in near bore area will be isolated by the aqueous phase trapping and unable to penetrate, and it is the main formation damage. This will be helpful in improving wellbore stability in basin deep shale gas drilling, reducing formation damage, and promoting drilling and exploration efficiency.
Unique Flow-Back Chemistry for Enhancing Productivity of Low- Permeability Reservoir
Authors: Zhang Hui , Marinescu Pavel , Foxenberg William
Published: July 2012

Low-permeability reservoirs are highly sensitive to water saturation. When filtrate or clear brine is lost into these formations, capillary forces pull the fluid into pore spaces and prevent full displacement upon production. This paper illustrates how effective flowback chemistry reduces water saturation and enhances productivity. The authors initiated a study to evaluate chemistries that can be added to reservoir drill-in fluids, completion brines, and workover fluids to reduce capillary forces, recover invaded brine from the formation, and promote optimal productivity of the well. This paper introduces a unique flowback chemistry that not only provides excellent surface tension reduction and good thermal stability, but fulfills a challenge not met before; i.e., it is completely soluble and compatible with all common types of completion brines. Furthermore, this chemistry is not absorptive to solids in drilling fluids or a porous formation matrix, therefore low surface tension and low capillary pressure are maintained with mud filtrate or brine that is lost to the formation. Simple, low-cost, and innovative methodologies are presented to illustrate capillary pressure reduction and brine recovery in a simulated formation.

Due to the nature of surface activity, flowback treatments containing surfactants invariably generate strong and long-lived foam. If not controlled, foam can cause difficulties or even catastrophic outcomes for well service jobs including fluid transportation, well circulation, and brine reclamation. The flowback chemistry presented in this paper includes a new and very effective defoamer (or antifoamer,) which renders the flowback treatment non-foaming. Successful lab tests and field application are presented.
Pore Pressure and Fracture Gradient Prediction in Shale Gas Formations: Accounting for Complex Rock Properties and Anisotropies
Authors: Li Shuling , Purdy Cary , Wu Shiguo
Published: July 2012

The prediction of abnormal pore pressure is necessary for avoiding, or at least mitigating, drilling risks but is even more critical in shale gas formations where pore pressure can increase from normal pressure to an abnormally high pressure over a comparatively short depth interval. Arguably, the pore pressure prediction in shale gas plays offers even greater challenges than conventional reservoirs. There are numerous reasons why shale gas presents additional challenges. First, anisotropic rock properties in shale formations thataffect log responses will also affect pore pressure prediction. Second, the presence of gas in the shale causes the compressional interval travel time to read higher (slower), which affects derived rock properties, negatively impacting the accuracy of conventional pressure prediction techniques. Third, the geologically-old formations have higher resistivities with complex compaction and uplift histories. The same properties that create challenges with pore pressure prediction also cause uncertainties in fracture gradient prediction.

New pore pressure prediction methods have been developed to address the unique characteristics of unconventional gas plays. The new methods incorporate gas corrections in the calculation of pore pressure and fracture gradient. Becausethe shear wave velocity has a much smaller gas effect than the compressional wave, it is used to correct the compressional data. Based on the corrected compressional log data, a better pore pressure prediction can be achieved. For resistivity-based pore pressure prediction, a new depth-dependent compaction, which accounts for complex compaction and reduces the gas effect, is used for improved pore pressure prediction. Additional improvements in the prediction of pore pressures, fracture gradient, and minimum stress are achieved by characterizing the effects of shale property anisotropies (e.g., Poisson's Ratio). The improvements achieved with the new methods are demonstrated through comparative analyses with conventional methods in the Bossier and Haynesville shales.
Dynamic Modeling of Wellbore Pressures Allows Successful Drilling of a Narrow Margin HPHT Exploration Well in Malaysia
Authors: Nordin Noor Azree , Umar Lawrence , Aziz IntanAzianBt A , Nas Steve , Woo Wing Keat
Published: July 2012

Using a Dynamic Hydraulic and Well Control Simulator to predict and establish wellbore pressures in a narrow margin HPHT well has allowed the operator to set operational limits during drilling, tripping, casing and cementing operations. A previous attempt to reach the objectives for the well failed. A much more rigorous approach to wellbore pressure management was undertaken prior to drilling this second well. A complete review of the expected pressure limitations was conducted, this review included a detailed overview of pore and fracture pressures as well as casing setting depths, hole sizes, temperature effects and proposed mud weights. This resulted in an improved prediction of the pressure windows for each of the proposed hole sections. Each hole section was in turn reviewed for optimal mud weights and this included a detailed review of equivalent static, equivalent circulating and dynamic kick tolerance limitations for the proposed mud weights. Surge and Swab calculations then determined maximum tripping speeds and cementing calculations ensured that pore and fracture pressure limits were not breached with the proposed cement volumes and pump schedules.

This paper presents the approach that was taken in proving a complete pressure management system for a narrow margin HPHT exploration well. The use of dynamic hydraulic models allowed accurate predictions of down hole pressures during virtually all drilling operational phases a hole section. Calculated down hole pressures were compared to PWD tools, proving that the accuracy of the dynamic hydraulic predictions was within the required limits to allow drilling without a PWD tool if required. Combining the available pore pressure and fracture pressure data, with mud weight schedules, pump rates, tripping rates and cementing operations allowed optimization of the drilling parameters thus ensuring that this narrow margin HPHT well, was drilled successfully to its target depth and all of its objectives were met.
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

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

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

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

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

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

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

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

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

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

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

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

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

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

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.
Drilling and Frac Stimulation Waste Management in Unconventional Gas Projects in Sichuan, China
Authors: Zhu J. , Chen J. , de Blok G.
Published: July 2012

Waste management will play an important role in delivering an environmentally sound well. If, however, a project requires the operator to drill hundreds of deep development wells and in close vicinity of communities, waste management even becomes a critical success factor. There is simply no room for error. The drilling and stimulation of these large number of wells will generate large volumes of solids and fluid waste, which must be managed efficiently, strictly controlled and comply with the requirements of local regulators.

Waste generated during the drilling phase constitutes of Water Based Mud [WBM] cuttings, Synthetic Based Mud [SBM] cuttings and WBM fluids, whereas frac flow back water will be the constituent following frac stimulation. To encompass all of these waste streams in an integrated waste management system, the project team of Fushun and Jinqiu [Sichuan, China] initiated a plan to cover waste generation, waste transportation, final disposal process and a waste tracking system as per ISO guidelines and in agreement with the Company's global Health, Safety & Environment [HSE] policy and procedures.

The waste management is divided in two phases. In Phase I the solution sought is to utilize a recycling method in the field to minimize the generated waste volumes. This comprises a disposal waste stream for each waste category. For WBM cuttings, solidification and burial in-situ would minimize the impact on drilling operations. For WBM waste fluid and frac flow back water, in-situ pre-treatment and then transporting these effluents to industrial waste plants has proven to be a workable and efficient solution. In contrast, OBM cuttings are treated as hazardous waste and are incinerated in a hazardous waste disposal plant.

There are a number of challenges to face, such as heavy land transportation, resistance from local farmers in a populated area, meeting the strict and the mandatory requirement from the Environmental Protection Bureau [EPB], whilst at the same time aiming for overall well cost reduction and project delivery. Another limiting factor is the number of qualified local waste disposal vendors in the Sichuan area.

But when there are challenges, there will also be opportunities. This paper aims to focus on these opportunities and will thus home-in on Phase II, currently under development, which comprises a pit-less drilling and stimulation approach, with all waste transported to a dedicated waste plant and waste disposal location.
Successful Application of ESPs in Bohai Bay Development
Authors: Sheridan Ed , Janjua Zia , McRae Jim , Paranji Sanjay , Long Michael
Published: July 2012

In 2002, during front-end planning for a project in China, the operator Anadarko understood that the electrical submersible pumping (ESP) system run life would be one of the critical factors for the project's success.

Therefore, consideration of the complete ESP lifecycle was taken into account. This included design, equipment specification, contracting strategy, installation practices, commissioning procedures, operating practices including optimization and troubleshooting, as well as ESP teardown and inspection.

The challenge was to provide ESP systems that could:

Cover initial low productivity index (PI) / low fluid rates Cover final high PI / high fluid rates Produce heavy oil Meet all the above conditions while keeping the ESPs within their operating envelopes

This drove the concept developed for the ESP design. The principle is still being used more than six years since its first production.

The final design included the following features:

Encapsulated ESPs to assist with motor cooling at lower fluid rates and heavy oil production Pumps with abrasion-resistant technology selected to cover the required large range of flow rates Geothermal-specification motors to allow operation at higher temperatures Comms-on-power down-hole sensors for continuous monitoring and optimization

Since coming on line, ESPs have been installed and operated very successfully in the CFD group of fields and have been exceeding all run life expectations. Of the 110 ESPs operating, the average run life since the start of production is 3.5 years, with 30 (28%) running more than four years and the longest ESP run life so far at 6.1 years.
Hybrid Fracturing Treatments Unleash Tight Oil Reservoirs Consisting of Sand Shale Sequences in the Changqing Oilfield
Authors: Zongqiang Zhou , Lijun Mu , Xianwen Li , Wen Zhao , Xiaodong Wang , Xiangqian Bu , Wenxiong Wang , Peng Pang
Published: July 2012

Low reservoir permeability and pressure are the key characteristics for the tight oil reservoirs consisting of sand and shale formations in the Changqing Oilfield in the Ordos Basin. In these tight reservoirs, regular fracturing stimulation with modest treatment sizes only yields low post-treatment production that cannot meet development requirements. Recent literature is bountiful in the successful developments of tight oil and gas reservoirs, especially from North America. After conducting literature review and learning from the experience in North America, hybrid fracturing tests were carried out in vertical wells, to improve well stimulation effectiveness in the Changqing Oilfield. Hybrid fracturing treatments for these tested wells yielded very good results with production enhancement at approximately 300% folds of regular fracturing treatments in the same reservoir block. Downhole microseismic fracturing monitoring and production analysis techniques were used to evaluate hybrid fracturing performance. In this paper, the ultra-tight oil reservoirs in the Changqing Oilfield were described, and hybrid fracturing treatments applied to the Chang 7 formation were studied with the aid of minifrac analysis, microseismic monitoring and post-treatment production results.
Hydra-Jetting Staged Horizontal Completion via Multiple Sliding Sleeve in Changqing Sandstone Tight Gas Reservoir
Authors: Yonggao Xu , Zhenfeng Zhao , Yajuan Wang , Yanming Zhang , Xu Ma , Kuangsheng Zhang , Xuangang Lai , Changjing Zhou
Published: July 2012

Changqing sandstone tight gas is characteristic of low-permeability and low-pressure, which is difficult to obtain economic benefits without fracturing. A new multistage fracturing technology for horizontal gas well is used in tight sandstone gas reservoirs. The new technology is hydro jetting-based and control the nozzles by opening the sliding sleeve by ball setting. With no need of packers and slugs, the technology realizes the integration of perforating, fracturing and isolation, achieving fracturing multiple stages in a single trip.

Field trials of 64 wells show that the new technology is simple and reliable, which is capable of meeting the requirements of rapid isolation and multi-fracturing in gas wells. The new technology opens another door for multistage fracturing horizontal well of sandstone tight gas and make the reservoirs have economic development potential.
The New Development of Multi-Stage Fracturing Technology of Multilayer Vertical Gas Wells In Sulige Tight Gas Field
Authors: Tianshou Zhu , Gangdan Fu , Yong Ren , Huaguang Zhang , Fenxia Zhao , Jie Gui , Zaiqiang Wang
Published: July 2012

In Changqing gas field, it is very usual that a gas well contains many gas bearing beds, whose property is different with each other. Because of the low formation pressure and low permeability, the nature rate is so small that every well must be treated. However, when treating these multi-layer wells, the conventional separate fracturing is not effective or cost-effective, and needs long time. To make all the beds treated effectively, to improve individual well producing rate and enhance economic benefit, optimizing several kinds of separate layer treatment technology and analyzing the feasibility of commingled producing in Changqing gas field. In 2005, a new completion string has been introduced[1∼5], which is achieved by plugging of the packers and opening of the sand blast sleeve. Using this technology and completion string, three formations can be fractured continuously, but needn't kill well. Firstly, perforating all the three gas layers at a time, at the same time assembling the completion string, then tripping it in the gas well; secondly, launching a ball to make packers set down, and fracturing the lower most layer; thirdly, launching a ball again to open the upper sand blast sleeve so that the upper layer is connected with the tubing and isolated with the sub layer, so the second layer can be fractured. Similarly, and the last layer can be treated like this step. Finally, when all the layers have been treated, unloading liquids of all layers, blowouting and producing. During fracturing, if sand plug happens, it can be solved by reverse washing. The strong point of this technology is that all the processes are made in the same string and needn't exchange string. From 2006 to 2009, the separate fracturing string with packers has been used more than 2000 vertical wells that cover 2 or 3 payer-beddings.

However, there are more and more vertical wells that contain far more than 3 layers, even to eight layers. So it is necessary to develop the separate layer string for fracturing at least 4 layers. This paper describes how to achieve this aim by intrducing new tecnnologies such as TAP fracturing technology, coiled tubing fracturing technology and modifing the initial fracturing string so that eight layers can be fractured with only one trip.