bluuebunny/crossref_metadata_2025 huggingface dataset:
Implement Fine Redevelopment to Keep Old Oilfield Sustainable Development —A Case from the T2k1 Reservoir of the Eastern District No.1 Block of Karamay Oilfield
Authors: Yang Shengzhen , Xiao Chunlin , Lin Jun , Yuan Shuwu , Wu Rangbin
Published: July 2010

The redevelopment of the T2k1 reservoir of the Eastern district NO. 1 Block of Karamay Oilfield is a pilot tracey of II conglomerate reservoir of Karamay Oilfield. Through a variety of technologies of detailed descriptions of reservoir, recalculating the amount of resources and the dynamic flow lines as well as evaluation of watered out zone etc, optimize simulation model, refine and quantify the remaining oil and recognize the potential reservoir comprehensively. Based on the evaluation of well pattern in history, combined with reservoir engineering, numerical simulation methods, optimize wellnetwork and well-spacing and rebuild well-network structure, implementing the secondary development. After adjusting reservoir development plan, carry out research of rational exploitation limit, fine water injection and reasonable regulation of pressure field, achieving stable production of secondary development. Through the fine secondary development succeeded in making an already developed 50 years and nearly abandoned oil reservoir once again rejuvenated. Furthermore, yearly oil production of the old oilfield rose from 1.5 × 104t to 7.1 × 104t, the ratio of adjustment wells obtain the design rate is up to 94%, the proportion of achieving production capacity is 107%. Successful explore and form a series of technologies to make the production steady after redevelopment of the II conglomerate reservoir of Karamay Oilfield, which have a very important significance for old oilfields to achieve sustainable development.
Lessons Learned from Stimulation Treatments and Filter Cake Removal Practices in High Permeability Carbonate during the Drilling Phase
Authors: Al-Mutairi Saleh H. , Al-Dhufairi Mubarak A.
Published: July 2010

In permeable carbonate formations, hydrochloric (HCl) acid treatments are usually utilized to remove formation damage and mud filter cake induced by drilling operations. Usually, the practice is to implement these stimulation activities after the rig is released and permanent completion is set. In some cases, these stimulation treatments cannot be performed due to tight project schedules and the need to deliver production/injection targets on time with minimum risk and environmental impact. These unique scheduling issues dictates stimulating the well before landing the production string and while the rig is on-site to save rig time and minimize expenditures. Yet, stimulating the well in this situation will increase its injectivty, which may lead to severe lost circulation problems and potentially serious well control issues. The objective of this paper is to present several field cases designed to achieve effective stimulation treatments while combating the issues of lost circulation.

Several stimulation recipes were studied in the lab and deployed in the field trying to address the goals of having a recipe that provide stimulation mechanism with the highest safety commitment and controlled investment. For example, acidic brine with different HCl concentrations, enzymes and organic acids were used. These recipes were applied during the cleanout trips after reaching total depth of the well. Therefore, they were used to displace the drilling mud out of the hole. As the displacement began, immediate lost circulation (100 barrels per hour (bph) to 150 bph) took place, which hindered well safety. Losses were beyond the rig pump capabilities and mandated immediate curing processes with Hydroxyethyl Cellulose (HEC) Polymer pills, which damaged the well again.

This paper details the experience gained from stimulating more than 10 wells where acidizing jobs have been performed before running the completion. It discusses efforts and techniques utilized to stimulate these wells but allowing the rig to perform casing clean out, mud displacement, pulling out assembly, and running the completion without encountering losses. Normally, this process takes an average of 3-to-5 days to complete. Subsequently, all tried stimulation recipes caused early lost circulation with varying degrees of severity. Lessons learned from these treatments are studied in this paper. These lessons were beneficial in optimizing and integrating stimulation and drilling activities. These synchronized efforts proved realized cost savings and fast turnover of wells.
Scientific Evaluation of Energy Consumption in Gas Plants to Promote the Optimization of Processing Facilities
Authors: Qing Li , Yie Liu , Yu Zhao , Qiumang Li
Published: July 2010

Energy consumption level is an important indicator to determine whether the process flow and process equipment are reasonable and optimal. Energy consumption levels of different gas plants and production units are different because of many influencing factors. Therefore, it is hard to evaluate the energy consumption levels of different gas plants and production units. Study has been done in this paper trying to solve this problem.

Firstly, influencing factors of energy consumption in gas plants are analyzed and categorized by inherent factors and non inherent factors. Theoretical studies of energy consumption have been made as to each unit in gas plant. By studying of energy consumption technological process and mediums, models are built for each production unit and relevant correlations have been established. A new concept of "Baseline Energy Consumption Value (BECV)" for gas plant and process units is introduced. Secondly, the process parameters at Baseline operating condition for different production units are stipulated in accordance with relevant standards, recommended practices and optimized operating paramenters. Then the BECVs of each production unitand a gas plant can be calculated. Finally, three typical natural gas plants are taken as examples for calculating of BECVs. The calculation results are analyzed versus the actual energy consumption values. Then the energy consumption levels of each plant and unit can be evaluated.

By the study of energy consumption of each production unitand gas processing plants, the bottlenecks of energy consumption in gas plants can be defined and the existing problems can be found. Plans for further process optimizations and energy saving modifications of process system can be made based on the evaluation results.

The theory and methodology proposed can be further implemented to other fields including oil fields and refineries for energy saving management and process optimization.
The Dynamic Analysis of Dry-Gas Reinjection in a Waterdrive Gas-Condensate Reservoir—Case Study: Yaha Gas-Condensate Reservoir, Tarim Basin, West China
Authors: Yuwei Jiao , Baozhu Li , Yong Li , Wei Xie
Published: July 2010

For relative high condensate content gas reservoir, dry-gas reinjection is an effective way to increase condensate recovery. However, the fluid phase behaviors are complex, and it is much important to carry out detailed performance analysis which contributes to reasonable adjustment programs for better effectiveness. According to Yaha gas-condensate reservoir, this paper presents following detailed dynamic analysis methods in order to research the effect of dry-gas reinjection according to Yaha gas-condensate reservoir.

Firstly, the pressure decline rate is in inverse proportion to the injection ratio, and the rate of pressure depletion is 1.29MPa/year while the reinjection ratio is 60%. As a result of the pressure decline, the characteristics of formation fluid change in different scale: the content of condensate and the saturation of retrograde condensate decrease gradually, and the dew point pressure increases slightly. Through careful comparative analysis it is found that the rate of GCR of certain wells increases three times faster than that before dry-gas breakthrough. Confirmed by trace monitoring the high permeability zones of dry-gas migration could be identified more accurately. Based on material balance equation analysis and numerical reservoir simulation, Yaha gas reservoir is of strong water-drive, and the edge water has moved forward about 300m in average, while 900m for some zones after nine years' development. Furthermore, the relative production and injection rates of different layers are found to vary from 0 to 90% through production log analysis.

According to the findings of performance analysis, some measures, such as infill well drilling, have been applied to Yaha gas-condensate reservoir in order to increase condensate recovery.
Analysis of Cement Sheath Coupling Effects of Temperature and Pressure in Non-Uniform In-Situ Stress Field
Authors: Li Yong , Liu Shuoqiong , Wang Zhaohui , Yuan Jinping , Qi Fengzhong
Published: July 2010

Whether zonal isolation is effective or not, is always an issue attracted much attention during oil exploration and development. Moreover, it concerns the whole oil well's long-term, safe and efficient production. The integrity of cement sheath is one of the important factors concerning zonal effective isolation. A large number of field examples and laboratory studies have shown that the variation of cement sheath stress caused by later operation is the major reason leading to the damage of cement sheath's integrity.

The variation of wellbore temperature and pressure during different operating jobs(such as fracturing stimulation, acid treatment, heavy oil thermal recovery, etc) will influence the magnitude and distribution of cement sheath stress. Excessive stress will lead to the damage of cement sheath. Therefore, an analysis about cement stress considering variation of wellbore temperature and pressure during production process has very significance for forecasting the integrity of cement sheath and zonal effective isolation.

For the first time this paper has comprehensively considered the influence of non-uniform in-situ stress field, temperature field and pressure field in casing, built a coupling mathematical analysis model of wellbore cement sheath. Through the methods of theoretical analysis of elastic mechanics, calculating programme programmed by computer language and graphical output, this paper presents a detailed analysis about the magnitude and distribution of cement sheath stress under non-uniform in-situ stress considering the variation of pressure in casing coupling with the influence of temperature. The study shows that increase of pressure and temperature in casing will remarkably change the magnitude and distribution of cement sheath stress. Specially, the inducing increase of tensile stress magnifies the fracturing probability of cement sheath. The research findings in this paper can be used to forecast the integrity of cement sheath during the performance history. Moreover, it can be a important guideline for the design of cement slurry.
Comprehensive Tapping Residual Oil Potential of Strong Water Drive Mature Oilfield in Southern American Rainfall Region
Authors: Li Yunbo , Jia Fenshu , Wang Genjiu , Chen Heping , Zhu Xinxi
Published: July 2010

Yanayacu Oilfield in Block 1AB/8 belongs to strong natural water driving oilfield with over 30 years development history in Peru rainfall region. The comprehensive water cut is 95% by 2005. This paper reviews a multidiscipline comprehensive study on potential tapping in this oilfield. Based on re-explained reservoir structure and secondary logging interpretation, as well as comprehensive geological study, fine reservoir 3D model was built and residual oil distribution was characterized. Reservoir simulation is conducted and result shows well pattern is the dominant controlling factor of residual oil. The well spacing is about 750–1000m, and there is no well drilled in structural high part in the north region, which leads to relatively enriched residual oil potential in the structural high part. The residual oil distribution is also affected by interlayer and barrier. According to residual oil distribution result, horizontal wells were deployed in relatively structural high part to tap residual oil, and re-perforation, layer transformation and bridge plug were applied in high water cut wells with interior barrier and interlayer. According to adjustment plan, two horizontal wells and one directional well were drilled in 2006, where the initial production of two horizontal wells is over 3300bbl/d, which is over 5 times of the highest initial production of previously drilled wells in this field. The comprehensive water cut of this field is dropped from 95% to 89.5% by the end of 2008.
A Study on Drilling Risk Real Time Recognition Technology Based on Fuzzy Reasoning
Authors: Lian Zhilong , Zhou Yingcao , Zhao Qing , Huo Zongqiang
Published: July 2010

Drilling risk real time recognition technology is vital important for drilling risk early detection, evaluation and control. Drilling risk symptom automatic extraction technology was studied. The maximum value, minimum value, average value, pick value, skew value and kurtosis value were chose as drilling risk symptom indicators, and time serial of real time data was set up. Signal changing tendency rate automatic extraction technology was realized. Drilling risk database was created, and inference engine based on fuzzy production rule was also realized. The application results of some cases indicated that the drilling risk real time recognition technology based on fuzzy reasoning is accurate and reliable, the drilling risk can be found in early time, and it can be used to monitor borehole complex situations in real time. Average value, peak value, maximum value, minimum value, skew value and kurtosis value can be used as drilling risk indicators
Application of Catastrophic Theory to Predict Wellbore Instability in Drilling
Authors: Shi Junfeng , Zhang Jianjun , Liu Yuzhang , Meng Xianwei , Jin Juan , Ling Fenqin , Liu Zhaowei , Wang Liancheng
Published: July 2010

Wellbore collapsing and formation leak off in drilling are all resulted from wellbore instability. So, researches on wellbore instability mechanism and its critical conditions can provide theoretical foundation on which is based to prevent wellbore instability in drilling. The paper introduces catastrophic theory for the first time to analyze wellbore instability mechanism and provide a new calculating method of wellbore instability thresholds in drilling. Taking the ground stress and the fluid seepage into account, the paper developes the potential energy function of rock around wellbore on the basis of the elastic-plastic theory. For the potential energy function, the catastrophic theory is applied here to analyze the mechanism of wellbore instability in drilling and obtain the safe range of mud density. Also, the paper analyzes the effect of some sensitive parameters. From sensitivity analysis, it indicates that the mud density results in wellbore instability chiefly, the trend of wellbore instability speeds up with the decrease of plastic zone permeability.
The Application of Shallow Horizontal Wells in Sudan
Authors: Liu Bingshan , Zhou Shi , Zhang Shunyuan
Published: July 2010

The two main target formations of shallow horizontal wells in Sudan are Bentiu formation and Aradeiba formation. They are becoming more and more important with the exploration of oilfield, and they are all about or shallower than 1000m underground. The stratums are loose, so some measures are adopted to ensure the success of drilling operations: studying the stability of the borehole, optimizing the hole structure and casing program, establishing the drilling fluid system and its formulation.

We get the pore pressure, collapse pressure, and the fracture pressure by studying the formation pressure system using professional software upon the logging data. Study the relationship between the content of clay and the stability of borehole. It shows that the clay content has significant effect to borehole stability in Sudan. Then we analyze the collapse period of the upper stratums. The time window is about from 5 days to 7days. Based on the results and the study of the data of those wells drilled, the horizons of leakage and collapse are indicated. According this and the formation pressure, we optimize the hole structure and casing program. Finally, the KCl-polymer system is sifted as the drilling fluid. We determine the mud density according to the formation pressure first. Then the contents of KCl and the additives are indicated by experiments. According the experiments, the ideal percentage of KCl is form 6% to 8%, and the percentage of QS-2 in the drilling fluid using in field is from 3% to 4%. Now there are 5 shallow horizontal wells have been drilled in Sudan. The research achievements have been applied in the drilling operations. The average drilling cycle is about 17 days. Moreover, the hole diameter enlargement rate is decreased remarkably.
Improvement of Flow Performance through Wettability Modification for Extra-Low Permeability Reservoirs
Authors: Qingjie Liu , Hongzhuang Wang , Pingcang Wu
Published: July 2010

The development of extra-low permeability reservoirs (air permeability<10md) is a crucial challenge due to the high injection pressure and low oil production. Many methods had been used for low permeability reservoirs to improve the performance, such as hydrofracturing, surfactant flooding, cycle injection, etc. It was found that the small pores dominate the fluid flow and displacement in low permeability porous media, so the capillary forces plays primary role in water oil displacement. For water-wet systems capillary forces assist brine imbibing into pores, whereas for oil wet case they tend to act as resistance. It is believed the wettability alteration from oil wet to water wet or to intermediate plays a beneficial role to lower the injection pressure and enhance oil recovery, but the flow mechanisms and the significance of wettability alteration for extra-low permeability reservoirs is ambiguous. A series experiments were conducted for investigating the effect of wettability alteration on relative permeability for oil-wet reservoir sandstones rock with air permeability range from 0.1 millidarcy to 2.0 millidarcy. The results indicate that both water and oil relative permeability curves are dependent strongly on wettability alteration. In particular, the co-flowing zones were extended remarkably and the recovery efficiency was improved by injection of thin film spreading agent solution.
A New Appoach for Rock Typing Used in One of the Iranian Carbonate Reservoir (A Case Study)
Authors: Jooybari H. Saboorian , Mowazi G. H. , Jaberi S. R.
Published: July 2010

It is safe to say that rock properties play the main rule in conducting fluid within porous media. Due to the fact that generally the rock data cover only a small portion of the reservoir it is necessary to find a technique to make use of them for the reservoir as a whole. This technique is generally referred as Rock Typing.

There are several methods for rock typing each of them has its own engineering base. The most commonly used methods are porosity-permeability cross plot, Archie's formula based method, capillary pressure, Leverett J-function and flow zone indicator (FZI).

All methods mentioned above have been discussed thoroughly and investigated to see if they are valid to be applied in this case study and it was noticed that none of them is useable. As such a new approach is developed to classify the rock properties of X-Reservoir.

The new approach has the advantage of including the tortuasity of the porous media which is totally ignored by all preceding methods. As a matter of necessity an analytical method was introduced to calculate tortuasity from capillary pressure curves. In fact the new approach applies tortuasity, connate water saturation in addition to capillary pressure, permeability and porosity values to classify rock properties to distinct units.

Based on the new approach three Rock Types have been figured out for X-reservoir. Besides, a Rock Index is extracted to assign a rock type for each grid cell of a simulation model based on its porosity.
A New Method to Describe the Formation Framework of the Volcanic Gas Reservoir Hierarchically
Authors: Lin Yan , Qiquan Ran , Yongle Hu
Published: July 2010

Natural gas of volcanic gas reservoirs in China is rich in resources, and its exploration and development is great potential, but the study of the volcanic gas reservoir is a brand new field, there are a lot of difficulties in this study field. Due to the key problem of describing the formation framework of the volcanic gas reservoir hierarchically, this paper break the study method of sedimentary reservoir, take XS 21 block volcanic gas reservoir in XS Gas Field, north Songliao Basin as the example, use outcrop, core, logging, seismic data and so on, according to the idea of "the control of magma source", present the "Volcanic edifice - volcanic facies- effective accumulating and filtrating body" volcanic formation hierarchical describing plan. Stressly, illustrate the Volcanic edifice identify and classify idea of confirm magma source-confirm surface-confirm body, and expound the concrete way to confirm volcanic crater by seismic section, seismic attribution and microtectonics, confirm surface of the volcanic edifice by outcrop, logging and seismic data, confirm body by 3D seismics. Though this idea and way, we identify and dissect the volcanic edifices in XS 21 block, and describe them quantitatively. This study is the base of the volcanic reservoir description and prediction, at the same time, it create a new way to study the volcanic reservoir more scientific than before.
Experimental and Simulation Studies of Steam Flooding Process in Shallow, Thin Extra-Heavy Oil Reservoirs
Authors: Zan Cheng , Ma Desheng , Wang Hongzhuang , Li Xiuluan , Guo Jia , Li Minzhi , Jiang Hang , Luo Jian
Published: July 2010

A three-dimensional model was built, representing one fourth of an inverted nine-spot flood pattern, and several parameters significant to oil recovery by steam flooding were scaled in the model size. The model was designed to simulate steam flooding of an extra-heavy oil reservoir in Xinjiang Oil Field in which the reservoir is shallow and thin. The growth of steam chamber and the mitigation of oil and water were monitored by using 243 thermocouples and 15 pressure transducers. Three different well configurations were investigated-vertical injection and vertical production well-group, vertical injection-horizontal production well-group and horizontal injection-vertical production well-group. Numerical simulation of steam flooding processes using different well configurations was performed. The CMG-STARS thermal simulator was used to simulate the data from the present steam flooding experiments.

The experimental results indicated that the combination of vertical and horizontal wells plays weak roles for improving steam flooding in the experimental model, because of the limited contribution by gravity drainage. The Maximum oil recovery was observed during the vertical injection-vertical production well-scheme with follow-up. During the early stage of the runs, the oil production rate and oil steam ratio of horizontal injection-vertical production well-scheme is significantly lower than those observed in other two well-schemes. For all of the three different well configurations, steam override severely affects the oil recovery ratio due to the low output from the lower part of the reservoir, which is the further research focus to improve oil recovery. Reasonable agreement is found between the results from the history-matched numerical simulation and those of the experiments for oil production rate, cumulative oil production and temperature profiles in the model.
Material Evaluation and Selection of OCTG and Gathering Lines for High Sour Gas Fields
Authors: Dezhi Zeng , Liming Huang , Shaoquan Huo , Yuanhua Lin , Hongjun Zhu , Yin Huang
Published: July 2010

Corrosion caused by hydrogen sulfide induces very serious consequences. In this paper, material evaluation and selection of OCTG and gathering lines were investigated for the high-sulfur gas fields in northeast Sichuan (more than 17% of H2S and more than 10% of CO2). For oil tubing, the corrosion behavior of VM80SS and G3 were studied by laboratory experiments. Then the experiments were rerun in the corrosive environment found in the Tian Dong 5-1 high sour gas well. Laboratory and field tests show that G3 could be used for well completion pipe in high sour gas fields. At the same time, for testing and evaluating the materials of gathering lines such as L245, X52 and X52/825 clad pipe, laboratory and fields test were also conducted simulating the corrosive environment of the North-east Sichuan high sour gas conditions. The results suggested that nickel-base alloy or clad pipe was a reliable and cost-effective anticorrosion measure for this application.
New Formation Evaluation Parameters of Low Permeability Water Bearing Gas Reservoirs and Its Application
Authors: Guangya Zhu , Xiangui Liu , Sheng Miao , Shusheng Gao
Published: July 2010

The developments of gas fields and laboratory experiments present that there are great differences in the well performance and well productivity between different wells with the same reservoir petrophysics. The characters and distributions of the tight gas reservoirs are not yet well interpreted by the current formation evaluation techniques. Based on the laboratory experiments by using the rate controlled mercury injection, nuclear magnetic resonance (NMR) and physical simulation technologies, the pore microstructure features of tight gas reservoir and its influence on the formation petrophysics were analyzed. Three new formation evaluation parameters for tight gas reservoir are proposed involving mainstream throat radius, movable water saturation and gas threshold pressure gradient (GTPG). Results of the constant-rate controlled mercury injection indicated that the mainstream throat radius is one of the key controlling factors for the petrophysics of tight gas reservoir. A good correlation-ship is obtained between the permeabilities and the mainstream throat radius. Results of core flooding experiments indicated that the pore structure have eminent influence on the GTPG. The GTPG is positive correlated with initial water saturation, and negative correlated with permeability. Results indicate that the absolute open flow potential (AOF) decreases with increasing GTPG. Water-blocking would occur and reduce deliverability of gas reservoirs, when gas displacement gradient is below GTPG. The GTPG plays an important role in determining the effective drainage radius and the abandonment pressure of gas well. The movable water and irreducible water could be identified by NMR method. Results show that moving water saturation (Smw) should be an assessment indicator to the water inflow of gas well. Incorporated with petrophysics, mainstream throat radius, gas threshold pressure gradient and movable water saturation a comprehensive evaluation method has been established. Applications of this method to some of the tight gas reservoir in China get reliable consistent results.
Interfacial Mass Transfer Mechanism and Flooding Characteristics of Dead End Pore on Supercritical Carbon Dioxide
Authors: Jishun Qin , Ke Zhang , Xinglong Chen
Published: July 2010

Enhanced oil recovery (EOR) processes are unavoidable fact, which will be applied in oil upstream industry. It seems the miscible gas injection into oil reservoirs be one of the most effective methods in EOR approaches. Therefore, the interfacial mass transfer and dead end pore flooding of carbon dioxide miscibility flooding take part an important role in oilfield. This study is mainly conducted by reservoir flow and supercritical fluid theory. Supercritical CO2 miscible flooding mechanism and a special dead end displacement mechanism are studied in ultra-low permeability reservoir. Besides, supercritical CO2 micro-flow characteristics and mass transfer between oil and CO2 are analyzed. Using a high-speed advanced and visualization camera (5000/s) micro-simulation model, the flooding mechanism of transient dead end pore and interfacial mass transfer are both observed. The oil film migration phenomenon and the miscibility are also clarified. During the flooding, the wax in crude oil continues to deposit at pore throat to form transient dead end. Supercritical CO2 could flood the oil in dead end by the cylinder and the cylindrical flow. As existence of molecular coalesces in supercritical CO2, it has a strong ability to dissolve heavy crude oil. This study will provide a theoretical support for CO2 crude oil miscible flooding in pilot test of permeability reservoir.
Water Flood Regime Study of High Dip Reservoir with Narrow Oil Zone
Authors: Junshi Li
Published: July 2010

To high dip reservoir with narrow oil zone, different water flooding regime has different development effect because of the affection of several factors. Geologic ideal models with different strata dip and permeability were built in this paper. By using these models, reserve recovery degree of crest flood and bottom water flood were calculated and compared though numeric simulation. Gravity and capillary pressure, as the most important affection factors, were considered during water flooding. According to geologic characteristics of one high dip reservoir with narrow oil zone in Mongolia, a new plate of reserve recovery degree was described, from which reserve recovery degree could forecast directly.
Deep Air Drilling Application to Enhance Rate of Penetration in Extremely Hard, Abrasive and High Temperature Environment
Authors: Nas Steve , Gala Deepak , Cox Paul
Published: July 2010

This paper details the lessons learned in late 2007 and early 2008 whilst air drilling vertical gas wells in the Travis Peak formation of the western East Texas deep Bossier play in Amoroso Field and applying the lessons learned in the US to a deep appraisal well drilled in Northern China.

The deep Bossier represents one of the most active onshore plays in the United States. Deep Bossier wells are 14,000 ft (4,267m) to 16,000 ft (4,876m) deep and intersect shale and sandstone formations ranging between 2,000 ft (610m) and 3,000 ft (914m) thick. The Travis Peak is also known as ‘tragic peak’ during conventional drilling operations because the sandstone is hard and abrasive in nature, leading to extreme low rate of penetration (ROP). Air Drilling technology was utilized to increase the ROP through the formation at depths of 10,000 ft (3,047m) and greater. The deep exploration wells in the Daqing area of Northern China are drilled to depths of 20,000ft (6,095m) and greater in an attempt to explore the deep volcanic reservoir potential in the area.

In the US the 8-1/2-in hole size was drilled using air hammers and roller cone bits using straight air or nitrogen. Temperatures in the Travis Peal formation were reported to be above 300°F (148°C). Temperatures in Northern China were reported to be as high as 400°F (204°C) in the 12-1/4-in hole size.

The fit-for-purpose equipment needed for the air drilling sections of these wells comprised of air hammers capable of drilling in high temperatures, hammer bits with full diamond inserts, high-temperature float valves, air compressors, nitrogen production units, mist injection systems, and rotating control diverters.

The lessons learned in the US were applied to the well in China where similar results were encountered. The drive to enhance air drilling to extreme depths and high temperatures previously believed to be off limits proved to be successful in both parts of the world.
Deepwater Managed Pressure Drilling Applications
Authors: Nas Steve
Published: July 2010

The growing interest in deepwater exploration drilling in the Asia Pacific region has resulted in the first exploration wells being drilled in the deepwater area's of South East Asia. As these deepwater exploration wells were being drilled, the first well control issues associated with kicks and losses in the carbonate formations have also been encountered. Over 200 wells have been drilled to date in South East Asia using managed pressure drilling techniques. MPD technologies are now routinely used on floating rigs to solve the loss kick scenario's encountered in the fractured carbonates, the use of MPD equipment in deepwater (+400m) operations provides a number of additional technical challenges that are now also being addressed.

This paper provides an overview of the current MPD applications and techniques used from floating rigs. The paper then highlights the unique challenges that are associated with the implementation of managed pressure drilling in a deepwater environment. In the near future as reserves are discovered and developed in the deepwater carbonate reservoirs, solutions to the drilling challenges will have to be found to allow commercial development of these deepwater reserves in the Asia Pacific Region.
Study Damage of Rock and Evolvement of Porosity and Permeability Under Hydraulic Fracture in Ji Lin Oilfield
Authors: Zhao Wanchun , Sun Chengyan , Wang Chen , Ai Chi , Bu Zhidan
Published: July 2010

Firstly, in view of the mechanism of rock damage of hydraulic fracturing for oil reservoir and considering the changes of matrix porosity and micro-cracks volumes for loading on the rock, the tensor damage variable of rock damage are defined by using the changes of matrix porosity and microfracture volumes and the rock damaging deterioration model of hydraulic fracturing is obtained based on damage theory. Secondly, assuming the dynamic evolution of micro- fracture of the process of hydraulic fracturing satisfy with the Logistic fork standard model, the microfracture dynamic evolution model is established based on the damage theory and according to the conservation of energy principle of hydraulic fracturing, the relation among the strain, medium porosity and damage variable of the process of rock damage evolution is determined. Finally, the model of matrix porosity and the evolution of permeability tensor of Micro- fracture for hydraulic fracturing rock is established. Take one well in Ji-Lin oil field as object, the regularity for change of parameters of rock were obtained.
Flow Induced Corrosion of API Round Thread Connection
Authors: Hongjun Zhu , Yuanhua Lin , Dezhi Zeng , Deping Zhang , Zhi Zhang , Yongxing Sun
Published: July 2010

Reservoirs with high pressure and high temperature (HP/HT) situated in Northeast Sichuan of China contain high content of acidic components such as carbon dioxide, hydrogen sulfide and element sulfur. The developing conditions of these reservoirs become more and more severe for intense corrosion, which gives rise to short service time of well tube. Then serious safety accidents and environment problems would happen frequently. So investigation of corrosion mechanism and preservation technologies of well tube is very important.

Previous published papers usually focused on crevice corrosion, bimetallic corrosion and phase-change induced corrosion. However, corrosion channels are generally found in tube connecting, where the flow velocity is smaller than that in tube. This phenomenon may be explained by the flow induced corrosion. So in this paper, based on the computation fluid dynamics, governing equations of flowing fluid have been bulit. Then flow characteristics in the connection of API round thread tube were simulated. Flow field accompanied by the occurrence of vortex is changing in the tube connection, resulting in accelerated corrosion reaction, cavitation corrosion and erosion-corrosion. As time goes on, morphology of flow induced corrosion would in turn affect the flow rate, which intensifies the corrosion. Finally, some technical measures to reduce flow induced corrosion were proposed. Calculation results of this paper can provide some references to design safe well tubes and operating parameters.
Accurate Matching of Bit and Reamer Tools Delivers Optimized Drilling Performance
Authors: Barton Steve , Weeden Ryan
Published: July 2010

The increased use of hole opening tools remote from the drill bit has led to a critical need to understand the interaction between the drill bit and the hole opening tool itself. Problems that can result from improper matching include vibration, inability to open hole, mechanical damage to string tools or to the bit, and sub-optimal drilling performance.

This paper explores the theoretical relationship between bit and reamer and modeling the relative aggressivity and stability of both tools, building on already established indices for predicting and comparing the performance of bits. It reviews the calculations and methodology of placement and development of both the bit and reamer for optimal interaction and performance. It also considers stabilization of the hole opening tool using both concentric and eccentric devices.

The paper also reveals the development of an interactive, intranet tool. This software incorporates logic regarding the configuration of the reamer and assesses these against key characteristics of the drill bit. The tool enables the user to accurately select the drill bit that best complements the reamer that will be utilized.

A number of examples from global applications are presented. These demonstrate reduced vibration, improved hole quality and hole opening performance, superior penetration rates, and overall significantly reduced drilling costs.
Eliminating Subjectivity in History Match Evaluation Through Systematic Data Mining and Application of History Match Quality Index
Authors: Darman Nasir , Bui Thang , Moreno Juan Carlos
Published: July 2010

History matching is a process in which one investigates the most uncertain parameters of a reservoir model and adjusts them to achieve the best possible match with observed data. Although there exist standard processes for history matching, from manual methods to computer-assisted workflows, reservoir engineers with all levels of experience continue to find the assessment of matching quality a challenge.

This paper compares three methods of assessing the quality of a history match: expert opinion, the Sum of Square of Error (SSE), and use of a History Match Quality Index (HMQI). Expert opinion, which is based on detailed visual inspection of modeled results, provides a sufficient assessment. However, it is often subjective and depends heavily on the reviewer's experience. The widely used weighted Root Mean Square (RMS) error (frequently used as an equivalent of SSE), which measures the degree of mismatch, is often affected by data outliers. Thus, it may not be practical in special cases.

The HMQI method first assigns the match quality index a value of either 0 or 1, to classify the quality of match for each data point. The history matching quality index for each simulated parameter of a well is defined as the weighted average of all points. In addition, one can use Moving Linear Regression Analysis (MLRA) to analyze observed data. The MLRA identifies data trends and automatically removes outliers, depending on the confidence level used in the analysis. Then one uses the confidence interval obtained from MLRA to estimate the tolerance level in ranking the match quality index.

We demonstrate the application of these methods and compare their relative merits in assessing the result of history matching in a mature oil field. MLRA clearly proves its ability to identify data trends and outliers. Combining MLRA and HQMI yields a superior and more robust quantitative result, compared with the other two most common methods: expert opinion and RMS error.
Currencies and their Effect on Planning in the Oil and Gas Industry
Authors: Harden James
Published: July 2010

As the rise or fall of crude prices have a close correlation to the costs of oil and gas exploration and development, E&P companies should understand how the effect of a weaker or stronger US$ can affect their planning and budgeting. The purpose of this paper is not to discuss global or national spending, debt, economic growth or GDP, trade imbalances or geopolitical issues that may have caused this the dollar to weaken to rapidly (or perhaps, non-US currencies to strengthen). The purpose is, instead, to provide E&P business and strategic planners to better understand the relationship between currencies and oil prices. This understanding may assist in valuation, price forecasting, cost budgeting and capital timing requirements for the massive investments that are required to meet the world's growing energy needs.

In this paper, original analysis of historical currencies (e.g., United States dollar versus Euro) and their correlation to oil prices are examined; as well as relationships of currencies and crude price effect on public equities and the cost-of-capital implications for global and independent energy companies. Also discussed will be the relationship between oil prices and drilling contract dayrates; as well as methodology to assist in analyses of prospective dayrates.

The USD began to devalue in 2002 and the current economic cycle could last much longer than some contemporary scholars believe. It is imperative that engineers and business planners understand key economic and financial drivers when making investment decisions. The reader should gain a better understanding of how oil price and currencies affect their cost-of-equity, and how one may use macro-economic indicators when performing financial analysis and projections.
Core Testing Provides an Engineered Approach to Underbalanced Drilling in Tight Gas Reservoirs
Authors: Yu David , Nas Steve , Zheng Fenghui
Published: July 2010

Core analysis of tight gas reservoirs can provide an engineered approach to the selection of underbalanced pressures required to drill tight gas reservoirs and thus avoid imbibition. A small number of core samples from the Ordos tight gas basin in China were tested for imbibition and phase trapping. The analysis conducted on these cores provided a direct indication of the level of underbalanced pressure required to avoid imbibition in this tight gas reservoir.

This paper will highlight the techniques used on the cores to establish the imbibition effect and the level of underbalanced pressure required to avoid the imbibition effects. The paper will then highlight some of the additional challenges that are encountered when conducting underbalanced drilling operations in tight gas reservoirs. The paper will discuss the significant benefits of underbalanced drilling in tight gas reservoirs and highlight why underbalanced drilling technology is extremely well suited to the successful development of tight gas reservoirs. The paper will further discuss the challenges that need to be addressed when considering the development of tight gas reservoirs through the use of underbalanced drilling.
Rheology of a New Gel Used for Severe Lost Circulation Control
Authors: Nie Xunyong , Luo Pingya , Wang Pingquan , Zhang Xinmin , yang Li
Published: July 2010

Lost circulation is a common problem in drilling project, especially the severe loss which consumes much material and costs much time, sometimes induced wellbore collapse, drill pipe sticking, overflow, blowout and well abandon at last. Based on theory of structure liquid, supramolecular chemistry, water-solubility salt-resisting and temperature-resisting polymer, we designed and synthesized the gel, called special gel, which is used to control severe lost circulation. When dispersed in water, a reversible supramolecular structure (dynamic physical cross-linking network) developed, which rendered the dispersion some special characteristics.

This paper investigates the rheology of the gel which is accordance with pseudoplastic fluid with yield point. The gel has thixotropy, good tackifying effect and shear-thinning behavior, and visible viscoelasticity. Those rheology characteristics show the gel has the potential to plug the weak zone. The gel is hard to be dilute by formation fluids for its apparent viscosity and strong cohesive force. Its shear-thinning property can provide the gel be pumped and flow in pipes easily, and flow with high viscosity and resistance in the zone porous. And its visoelasticity make the gel has high flood efficiency to cut off the connection between the formation fluid and the drilling fluid in borehole. It will impose a higher pressure to push the gel system after the gel stay. And the gel has good Compatibility with common use lost circulation materials such as walnut shell, cement. When the loss pressure difference is too high, the gel can be used with bridge plug or cement. The gel is benefit to control severe lost circulation accompanying with water zones or overflow and loss coexist. The gel was successful to deal with severe loss in Sichuan, Changqin and Tuha oil fields in China.
New Cutter Technology for Faster Drilling in Hard/Abrasive Formations
Authors: Plemons Billy , Douglas Charles , Shen Yuelin , Zhan Guodong , Zhang Youhe
Published: July 2010

Drilling the hard, abrasive and interbedded Travis Peak and Cotton Valley formations in East Texas creates a difficult challenge for polycrystalline diamond compact (PDC) bits. Historically, conventional PDC cutting elements dulled quickly due to abrasive wear, impact damage and thermal fatigue. Thus, cutter technology has been the limiting factor for efficient PDC bit drilling in the East Texas Basin.

Recent technological developments have produced a new, highly abrasion resistant cutter that has increased rate of penetration (ROP) and total footage drilled in addition to producing better dull grades. Further, the sections that normally require two/three PDC bits can now be drilled in one fast PDC bit run. The new cutter technology is designed and manufactured utilizing an innovative process which delivers superior properties both in laboratory testing and field trials. The manufacturing process involves a two-step high pressure/high temperature (HPHT) technique. The first step is to make a polycrystalline diamond table (PCD) using conventional HPHT parameters. The second step is to re-attach the PCD synthetic diamond wafer on a new tungsten carbide (WC) substrate under extreme HPHT parameters. The advantages of this method compared to the conventional one-step process are as follows: The residual stress in the PCD table is reduced by the additional second processThe two-step HTHP process increases the microstructure strength of the PCD

Laboratory tests have indicated the new type of PDC cutter has increased resistance to abrasive wear and thermal fatigue by approximately 100% over standard PDC cutters while not compromising impact resistance. Extensive field tests in the East Texas Basin have documented that drilling efficiency could be improved by 20% in the hard/abrasive application. The cutters are expected to have a positive economic impact on other hard/abrasive applications worldwide.