bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
The development of extra-low permeability reservoirs (air permeability&lt;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

Abstract
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

Abstract
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

Abstract
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

Abstract
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.