bluuebunny/crossref_metadata_2025 huggingface dataset:
Application and Prospective of Sand Management With Multilateral Wells by Means of Drilling and Completion Technology for EOR in Bohai Bay
Authors: Jiang Wei , Zhou Shouwei , Liu Liangyue , Zhang Chunyang , Fan Baitao
Published: December 2007

This paper summarizes the three big challenges in the development of the oilfields in Bohai Bay: most of the reserve is heavy oil; formation is unconsolidated and lower productivity after sand control operation. Through years of research and improvement, based on serious analysis of reservoir characters and oil production performance, method of drilling and completion and production management, traditional distribution of the mesh of directional well and conventional gravel pack sand control method are changed and an alternation of sand management multilateral technology is adopted to enhance the production and oil recovery with three technology characters: one is the control of the drop of production pressure under the condition of sand management, until this technology is applied in Bohai Bay, remarkable achievement is made in the field of enhance the production and oil recovery for the development of new oil field and the reboot of the older oil field, which has been one of the key technologies to apply to a large scale and continuously improve. It has been exerting a lot of pressure and positive influence on the technology of production, drilling and completion technology, and further performance of the EOR.
Application and Research of Latex Tenacity Cement Slurry System
Authors: Sun Fuquan , Lv Guangming , Jin Jianzhou
Published: December 2007

This article presents the stability research of latex tenacity cement slurry, develops the BCT series stabilizer and studies the performance of the slurry and the set cement. Due to the slurry performance study, it is found the latex material can be evenly distributed in the slurry, which can form a film to bond free water and micro particle, reduce fluid loss and prevent gas migration. Adding other additives to this system, the slurry shows better performance with lower fluid loss, better rheological behavior and adjusting thickening time. Due to the set cement performance study, it is found the latex particle can evenly fill in the fine gap of C-S-H gel. It assembles and forms a film to cover the CSH surface, which can decrease the set cement elasticity coefficient and permeability, improve its impact resistance and anticorrosive properties. Moreover, the application of this latex tenacity cement slurry system is introduced in this article.
Multiple-Stage Fracture Treatment of Horizontal Wells
Authors: Wang Feng , Zhang Yingan , Li Biansheng
Published: December 2007

Aiming at the actuality of horizontal well fracturing modified technology is complicated and limited entry fracture treatment is restricted in internal and overseas low-permeability oilfield currently. The studied and experimented that using packer performed the staged fracturing and corollary technique in annulus between tubing and casing, verified by 23 wells and 41 staged treatments in field with 100% of successful rate and effect of fracturing stimulation is very significantly. The full process of hydraulic motion includes setting, working and releasing were realized by the packer of annulus staged fracturing, and putting into well tools were reduced by horizontal well annulus staged fracturing technology as well as the accident sticking fishing corollary technique has been formed. In addition, annulus fracturing also have advantages of low fluid fraction, improving treatment rate and reducing treatment pressure, etc., multi-fractures removing plugging fracturing stimulation of long perforated interval can be performed, too. Thus, a new method has been developed for the horizontal well fracturing technology.

The fracturing treatment of the horizontal wells is one of the studying focus in domestic and overseas, staged fracturing technology of the horizontal wells applied in the oilfields mostly include horizontal wells selective interval isolation fracturing technology in overseas, changing horizontal wells gel staged fracturing technology in domestic, daqing oilfield horizontal limited entry fracturing technology and so on. At present, the horizontal wells fracturing technology is mainly restricted in limited entry fracturing. What this paper presents is the staged fracturing technology of horizontal wells in annulus between tubing and casing. Annulus treatment can reduce treatment friction efficiently with the ability of improving treatment scale, and supply the technology warrant of improving the horizontal wells development effect in low-pemeability oilfield.
Reservoir Characterization of Fractured Volcanic Gas Reservoir in Deep Zone
Authors: Ran Qiquan , Yuan Shiyi , Xu Zhengshun , Hu Yongle , Wang Yongjun
Published: December 2007

Quite a few large-scale volcanic gas reservoirs have been discovered in deep zone in Songliao Basin of North-East China in recent years. The consequent issue is how to produce this kind of gas reservoir effectively. Reservoir characterization is essential for the effective production of volcanic gas reservoir, which provides the geological basis for gas reservoir development. The geological scenarios of volcanic gas reservoirs are extremely complex, which is featured by quick changes of lithofacies and its thickness, distributions of fractures and pores/vugs, strong heterogeneity, changes of gas well productivities among different wells, etc. The difficulties of reservoir characterization pose a great technological challenge on effective production of volcanic gas reservoir. In this paper a systematic methodology is proposed for characterization of fractured volcanic gas reservoir based on a large amount of laboratory experiments, theoretical studies and field practices. The proposed methodology is a multi-discipline integration, including identification of lithologies and lithofacies, eruption period analysis and stratigraphic correlation, identification and evaluation of fractures, identification of volcanic body and reservoir prediction, well log interpretation for the dualporosity volcanic reservoir, discrimination of gas and water layer, reservoir appraisal and geological modeling, etc. These studies provide a strong base for making decisions on the reasonable well pattern and development plan.
A New Completion Technology with Separate Layer Fracturing and Commingled Producing in Gas Field
Authors: Gangdan Fu , Zhenfeng Zhao , Fenxia Zhao , Jie Gui , Changhao Yan , Yong Ren
Published: December 2007

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. Through 3 years research and piloting, a new completion string has been introduced.

This new technology is achieved by plugging of the packers and opening of the sand blast sleeve. Using the 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.

The technology has been used in about 150 gas wells till 2006, which indicates that it has advantage of favorable mechanical plugging, easy to implement, high rate of delivery, no damaged to formation, high completion well rate, low operating cost for single well. Therefore, the new completion technology and string is very perspective, especially for low permeable, low formation pressure gas reservoir.

This paper describes the principle, the parameater and function of each tool, operation procedure, advantages and application of using the technology.
The Oil Well Casing's Anticorrosion and Control Technology of Changqing Oil Field
Authors: Xu Yonggao , Yang Quan'an , Li Qiongwei , Chen Bihai
Published: December 2007

With the increasing oil production of Changqing oilfield, the casing's corrosion and damage have became more and more serious in producing and injection well system. After long term research, the corrosion mechanisms of casing were made sure, and two main technologies were developed to prevent the external and internal corrosion, respectively (Cluster wells’ CP and Epoxyn-bond tape plus zinc anode, Inner polymer coating and Downhole inhibitor injection facility). Three types of control technologies of well damage casing have been applied. The large scale applications of those technologies in Changqing oilfield not only inhibit the casing's damaged, and also keep the newly opened wells in a good condition. At last these new techniques guarantee the stable production of Changqing oilfield.
The Discussion About Software Demand Management and Development Standardization Management in a Chinese Oil Field
Authors: Yu Haiyan , Lu Dongfeng , Jiang Hongfu , Wang Tong , Cui Juncheng , Yang Haiying , Yuan Wencui , Zhu Ying , Shi Guojun
Published: December 2007

The next certain years, the main duty of information construction of the petroleum enterprise will be the omni-directional support oil industry core business. The software development and management in oilfield also will be important content of the oilfield information construction. Chinese oilfield cannot rely on domestic Software Company or foreign Software Company completely and blindly because of the specialization of the oilfield exploration development and the particularity of Chinese oilfield production and management. Absorbing the advanced software development management idea of Software Company, the Chinese oilfield should rely on own specialist and go out a path that suits the Chinese national condition and Chinese oilfield software development and management. In this process, the software development of Chinese oilfield has two weak sides at present: One is the software demand management; the other is development standardization management. This paper takes the Chinese some oilfield as an example, discusses with emphasis in view of the two weak sides in order to obtain the oilfield actual demand and standardization development.
A High-Efficiency and Low-Cost Exploration Data Management System
Authors: Li Ning , Wang Caizhi , Qiao Dexin
Published: December 2007

An exploration data management system, on which geologists, geophysicists and log analysts can work together with the same data source, is developed based on the broad band intranet environment now commonly used in oil enterprises and companies. In most cases, it is demanded that the operation visiting seismic data, log curves and remote images should be as simple, direct and batch as possible. For this reason, the design of our system is not depended on any commercial database. It is based on a simple data structure called CIF. In this way, we not only improve the visiting efficiency, but also reduce greatly the cost of the system installation and maintenance. Obviously, it gives a knowledgeable choice for those upstream oil enterprises and companies for their exploration data management. The server served in our system is a SunFire V490 with its Solaris 8 operating system. The end users, with their PC and Windows XP operating system, visit the data saved on NetApp hard disk array through 1GB fiber cable intranet. It is convenience for using the system to query and visit seismic, logging and remote data as well as several of multimedia files (such as .doc, .xls, .ppt, .jpg and .mpg etc.), and to display or download them. In 2005, the system was successfully installed and put into production in Research Institute of Petroleum Exploration & Development of

PetroChina in Beijing, and in China Petroleum Logging Co., Ltd. in Xian.
An Innovative Method: Risk Assessment for Exploration and Development of Oil and Gas
Authors: Chang Yuwen , Dou Hong'en , Chen Changchun , Wang Xiaolin , Liu Kun
Published: December 2007

This paper presents a new method and flowchart of risk assessment for the oil and gas upstream industry to identify and evaluate the risks in the oil and gas investment activities. It integrates several commonly used risk identification techniques, including fault tree analysis, brainstorming, and Delphi and event tree analysis methods. This paper divides the risk factors into three categories: social environment, natural environment and resources, technology and management, there are several risk factors in each category; therefore, a risk assessment system of the three hierarchies is built up. In the third hierarchy, a risk grade standard is established according to expected economic loss, which is determined by the risk probability and the consequence of the risk factors. A new method of the risk assessment was presented, Fuzzy Analytical Hierarchy Process (Fuzzy-AHP). The integrated risk grade of oil and gas exploration and development project can be obtained. In this method, the influence weight and the consequence of risk factors are comprehensively considered. It gives a significant reference for decision-makers of the oil and gas upstream industry. At present, this method has been recommended to the exploration and development risk assessment projects in the oilfields, China.
Quantification of Overbalance-Induced Invasive Damage and the Estimation of Equivalent Skin Effect on Production
Authors: Ramalho John , Wu Zhan , Vaidya Ravi N. , Suryanarayana P. V.
Published: December 2007

An important premise of underbalanced drilling (UBD) is the productivity improvement it delivers through mitigation of invasive damage. Characterization and quantification of such damage, therefore, becomes a pre-requisite for assessing the value delivered by UBD. Several methods are available to quantify damage. In this work, we use a novel approach that combines dynamic micro-scale reservoir simulations calibrated to special core tests to model the extent of invasive damage, and its impact on flow-back during production. The approach is based on special tests conducted on reservoir core, and a dynamic "micro-simulator" to model invasion during drilling. Special core tests designed to measure effects of overbalanced exposure to drilling fluids are first conducted. Inputs to the simulation model are based on careful interpretation of the core test results, and thus are calibrated to observation. Details of the approach were presented earlier by Suryanarayana, et. al. (SPE 95861). In this paper, we apply this approach to two field cases, and use the results to quantify the damage and its impact on production. The two field cases are discussed in detail. Both relative permeability and permanent damage effects are described. The dramatic effects of invasion on clean-up and long-term production are illustrated, thus demonstrating the incremental value of UBD in these cases. Damage can be modelled as an equivalent skin, based on the saturation and permeability profiles within the zone of invasion. Since the saturation and permeability effects are a function of location along the productive length as well as time, we obtain time- and spatially-dependent equivalent skin. The equivalent skin can then be used in field-scale reservoir models to compare different drilling and development options. The use of these results in designing an optimal drilling and completion plan to lock-in the value of UBD is demonstrated for the two field cases.
Air Injection and Waterflood Performance Comparison of Two Adjacent Units in Buffalo Field: Economic Analysis
Authors: Kumar V. K. , Gutierrez D. , Moore R. G. , Mehta S. A.
Published: December 2007

Buffalo Field covers a large area on the southwestern flank of the Williston Basin, in the northwest corner of South Dakota. In 1987, 8,000 acres of the field were divided into two units to initiate improved oil recovery operations with two different methods: air injection and waterflooding. After collecting 18 years of production history a comparison has been made between the two projects to determine the relative success of both units.

In a previous paper (SPE 99454) the technical comparison of the projects was discussed and the superiority of the air injection project was demonstrated. This second paper addresses the economic analysis of both projects in terms of economic parameters such as net present value, payout time, incremental profit and rate of return. A sensitivity analysis on some of the key drivers of the project economics namely oil price, operating cost and capital investment was also performed.

In spite of being technically less successful, the West Buffalo "B" Red River Unit (WBBRRU) under waterflooding has shown greater economic benefit over its "twin" West Buffalo Red River Unit (WBRRU) under air injection. This results primarily from the low oil prices (less than $20/bbl) experienced during most of the life of the projects.

This case study shows that for an air injection project to be successful not only technically but also economically, a sufficiently high oil price (greater than $25/bbl) is needed due mainly to the high operating costs and capital investment.

Air injection can be an economically attractive IOR process in large prospects, particularly in deep, high pressure, low permeability reservoirs where water injectivity is limited and other recovery processes become uneconomic.
Huff 'n' Puff Recovery Technique on Waterout Horizontal Wells
Authors: Wang Chunhong , Li Gaoming
Published: December 2007

After the bottom water breaks into a horizontal well, the traditional way to recover the left oil above the horizontal well is to plug in the section below water level (the horizontal section) and re-perforate in the vertical section. However, this practice loses the advantage of horizontal wells. This paper proposes a Huff and Puff recovery technique for horizontal wells after water breakthrough and this technique utilizes the whole horizontal well instead of just the vertical section to further the oil recovery. Huff and Puff process is a cyclic gas injection process often used to recover attic oil, which involves three steps: gas injection, shut-in and production. Through a parametric study, the important control parameters towards a successful Huff and Puff recovery project are identified. In the analysis, we consider the impact of hysteresis on modeling the recovery processes through a historydependent-modeling method taking into account of the hysteresis of both relative permeability and capillary pressure. The results indicate that ignoring the hysteresis can overestimate the recovery predictions up to 16%.
Optimal Well-Testing Strategy for Production Optimization: A Monte Carlo Simulation Approach
Authors: Bieker H. P. , Slupphaug O. , Johansen T. A.
Published: December 2007

Well testing may be performed to support many decisions including ones related to production optimization of an oil production system. In production optimization information such as gas oil ratio and water cut/water oil ratio is used to decide on, for example, which wells to prioritize for choking back/opening to avoid over-/underutilization of the production capacity. Since the reservoir properties change with time, the uncertainties of their estimated values increase with time, and eventually a new well test will be required. As the uncertainty in the estimates grows, so does the risk for prioritizing the wrong well(s) giving lower oil production rate than possible. A computer program is developed to decide which well to test based on historical test data. The program uses a Monte Carlo approach for identifying which well test is likely to lead to highest increase in the total oil production rate after the well test information is utilized to optimize the oil production. The computer program is applied to field data quantifying the benefits when applied to this specific field.
Estimating Major and Minor Natural Fracture Pattern in Gas Shales Using Production Data
Authors: Gaskari R , Mohaghegh S. D.
Published: December 2007

The U.S. Geological Survey estimates tight-gas sands and shales may contain up to 460 trillion cubic feet (Tcf) of gas in the U.S. alone - almost three times the amount of currently proven gas reserves - and that some 135 Tcf may be technically recoverable. Since natural fractures are the main source of permeability in gas shales, key to producing this vast resource is locating areas where natural fractures are abundant. By placing infill wells in such locations operators can significantly increase gas recovery.

In most cases, in fields that produce from gas shales, monthly production rate is the only data that is available. This paper introduces a new strategy for estimation of major and minor natural fracture using production data.

The framework includes the use of Geographic Information System as an environment to analyze the production data where the preliminary estimation of natural fracture trends is developed. Then by superimposing the results of the preliminary estimation on reservoir quality indices developed using a fuzzy pattern recognition technique, the uncertainty associated with the initial estimation is reduced. This technique is validated using a set of gas shale wells in Kentucky and West Virginia.
New Techniques for Plunger Lift in Conventional and Nonconventional Gas
Authors: Morrow Stanley J. , Hearn William , Cisneros Ramiro
Published: December 2007

The interest in and demand for natural gas has dramatically shifted the focus for many operators in the past few years. Plunger lift, which for many years was viewed as a last resort, and somewhat of a nuisance, has gained an all time high in popularity, and effectiveness and applicability. Most of the guesswork in evaluating candidates has been replaced with exotic programs that combine Nodal analysis with performance based calculations.

In recent years both equipment and applications have improved, and the production range of plunger lift now includes many wells previously not possible to produce with plunger lift. Here we will examine the new technology utilized in tracking, evaluating, and troubleshooting plunger lift wells. Also several case studies on where previously difficult production is now commonplace, will be presented.
Optimal Infill Drilling Design for Marginal Gas Reservoirs Using a Simulation-Based Inversion Approach
Authors: Cheng Y. , McVay D. A. , Lee W. J.
Published: December 2007

Infill drilling plays an important role in revitalizing marginal oil and gas fields by adding new reserves and accelerating recovery. However, design of an infill drilling program is often a challenging task for these kinds of reservoirs. First, most such reservoirs are mature fields where data are scarce and reservoir characterization is very limited. It is not uncommon for only production data to be available in a marginal, mature field. Second, the design often has to deal with a large number of existing wells and evaluate hundreds or thousands of potential infill drilling candidates. Given the marginal nature of these fields, a conventional evaluation approach, such as detailed reservoir characterization and simulation, is usually prohibitively time-consuming and costly. Furthermore, when designing an infill drilling program, well interference or acceleration effects have to be taken into account to reliably identify the potential for new reserve additions. Thus, an optimal infill drilling design procedure that adequately addresses these issues is extremely important.

In this paper, we present a systematic methodology for efficient design of an infill drilling scheme for marginal gas reservoirs. The approach consists of two major components. The first is a sequential inversion algorithm for rapid history matching. The algorithm is conditional to the correlation between permeability and porosity, if any. The inversion provides not only the spatial distribution of both permeability and pore volume, but also the spatial distribution of remaining gas in place. The second component of the approach is a successive selection strategy for infill candidate locations. The method fully addresses well interference effects between existing and infill wells, as well as interference between infill wells.

The approach is rapid and cost effective, and provides answers to critical questions such as: given certain economic criteria, how many wells should be drilled; where should the wells be drilled; what production performance can be expected; what will the incremental gas recovery be; and what will the acceleration effect be? Synthetic and field examples are provided to demonstrate the applicability and power of the method.
Improving Cement Bond in the Appalachian Basin With Adjustments to Preflush and Spacer Design
Authors: Newhall Chandler
Published: December 2007

Cement bond quality is imperative for all phases in the life of a well. Achieving a superior cement bond can be an engineering challenge in areas with naturally fractured formations. Often there is a driving force to lose the cement slurry to the fractures or for the slurry to be contaminated by formation fluid flowing into the wellbore from the fractures. Failure to effectively isolate these zones can be extremely costly over the life of the well. An inadequate cement bond can result in interzonal gas and liquids migration within the annulus, negatively impacting the recovery of hydrocarbons and increasing downhole scaling and corrosion tendencies. In severe cases, subterranean fluids can flow along the annulus all the way to the surface of the well, resulting in environmental contamination and expensive remediation.

This paper addresses how adjustments to pre-flushes and spacers have improved cement bond quality in the Appalachian basin. When drilling in the Appalachian basin, encountering hard sandstone, fractured shale, and coals with low pore pressure gradients is very common. The fractured shales and coals may present problems when cementing the well. These problems include cement dehydration due to excessive fluid loss or formation "breakdown," in which whole cement slurry is lost to a created hydraulic fracture. When this situation is encountered, it can be difficult to achieve proper cement tops and cement bond quality can be poor.

Field data was collected from Gilmer County, West Virginia. In the study area, the wells were drilled to the Alexander formation with compressed air. Cement jobs were historically pumped with the following schedule: gelled water, cement slurry and displacement. A re-engineered pump schedule now includes a dual chemical-spacer system ahead of the cement slurry. The leading spacer was a mixed cleaner/surfactant solution, and the trailing spacer was a filtrate-reduction solution that also enhances cement adhesion to pipe and formation. Approximately five days following the completion of both cement jobs, cement bond logs (CBL) were run on the wells and the results of each were compared.

As evidenced by the comparative analysis of the CBLs, the adjustment in the pre-flush/spacer design resulted in a marked improvement in the quality of the cement bond. These results are documented in the paper. The resulting impact of the modified design on well completion and operating costs are also reviewed. Mitigation of any environmental risks are quantified.
On the Flow Performance of Velocity Strings to Unload Wet Gas Wells
Authors: Oudeman P.
Published: December 2007

In depleted gas wells, the produced gas rate and consequently the velocity will drop to the extent that produced liquids are no longer carried to surface. The liquids accumulate in the well bore, increasing the sand face pressure. This further reduces the inflow, so that more liquid collects and eventually the flow dies down completely. This phenomenon is known as liquid loading.

Velocity strings are a commonly applied remedy to liquid loading in gas wells. By installing a small diameter string inside the tubing, the flow area is reduced which increases the velocity and restores liquid transport to surface. The disadvantage of the velocity string is the increase in frictional pressure drop, constraining production. Hence an optimal velocity string has to be selected such that liquid loading is delayed over a long period with a minimal impact on production. This requires accurate methods to predict pressure drop in the velocity string as well as tubing-velocity string annulus.

The available methods to predict pressure drop in annuli for gas-liquid flow are modifications of methods to predict wet gas pressure drop in tubing. These modifications are usually based on assumptions, which are strictly valid only for single-phase flow. Their validity for gas-liquid flow is questionable. Hence to assess the validity of the methods a field test was designed and executed. The results were compared with various approaches to describe wet gas flow in an annulus. This allowed selection of the best approach with an accuracy comparable to the accuracy of methods to predict pressure drop in tubing. Factors affecting the accuracy were identified. Comparison with a field case provided further proof for the validity of the approach.

This result is not only relevant for velocity string design, it is important for all annular flow processes in wells such as flow around a stinger, drill pipe, tool or coiled tubing string.
Hydrocarbon Potential Monitoring in Gas Sandstone Reservoirs Using TDT and CHFR Techniques
Authors: Hamada G. M. , Hegazy A. A.
Published: December 2007

The ability to detect and evaluate bypassed hydrocarbon and track fluid movement in sandstone reservoir is vital in the quest to improve production and increases recovery. The main technique, which has been used for monitoring reservoir saturations, is Thermal Decay Time (TDT) tool. But, it was hard to interpret the TDT data in the low formation water salinity reservoirs. This problem can not be solved because it is related to the theory itself of TDT measurement, which depends on salt content in formation brine. The problem of low formation water salinity was solved by Carbon Oxygen Ratio (COR) technique, which was latterly combined with TDT technique in the same tool, called reservoir Saturation Tool (RST) tool. This tool was not widely used due to its short depth of investigation (6-8 inches) in addition to its long logging time.

A Technique called Cased Hole Formation Resistivity tool (CHFR) technique was proposed to overcome many of the pulsed neutrons tool limitations. Based on the actual CHFR logs recorded through wells studied in an oil field in Sinai, which are presented and discussed in the present work, a comparison study was done between the two available techniques, TDT and CHFR as methods for reservoir saturation monitoring, in addition to the results of open-hole resistivity logs as reference runs. It was found that water saturations calculated from CHFR logs were more accurate than TDT log in most of the cases, and that the quick look of CHFR logs always agrees with its quantitative interpretation, which gives the trust to relay on quick look of CHFR log, if a fast decision is required. While the quick look of TDT log was found to be very tricky, in most of the cases: often does not agree with its quantitative interpretation.
A Case Study in the Removal of Deposited Wax From a Major Subsea Flowline System in the Gannet Field
Authors: Craddock H. A. , Mutch K. , Sowerby K. , McGregor S. , Cook J. , Strachan C.
Published: December 2007

The chemical removal and dissolution of deposited wax has been described and proven in a variety of applications. This paper describes in detail the removal of wax deposits from a major subsea flowline with the use of a chemical dissolver.

The following stages were key to the successful wax removal operation; selection and design phase of the chemical application, the chemical environmental selection criteria, the development of the work scope, as well as the mobilisation and logistics of the chemical application. This paper will illustrate the challenges faced as well as the novel monitoring and analysis techniques used in the field to determine the level of wax dissolution in situ.

The wax removal process was deemed successful and offered the client significant benefit in terms of increased oil production. Reduced pipeline differential pressure and increased fluid arrival temperatures also indicated that the wax restrictions in the flowlines had been significantly removed. In addition, the impact on the platform processing facilities during final fluid displacement was much less than anticipated and occurred with no major concerns.

A chemical dissolver application of this magnitude is thought to be unique, indeed a world first. The application was conducted in the Gannet D Field in the UK sector of the North Sea to remove wax deposits from two 16 km 6" subsea production flow lines.
The Application of Wax Dissolver in the Enhancement of Export Line Cleaning
Authors: Craddock H. A. , Campbell E. , Sowerby K. , Johnson M. , McGregor S. , McGee G.
Published: December 2007

Paraffin deposition in oil export pipelines can prove problematic during "intelligent pigging" operations, when hydrocarbon deposits on pipe walls are not removed sufficiently during the cleaning phase. This gives rise to sensor clogging and lift-off causing inaccurate and in some cases complete loss of data from the inspection tool. In pipelines where paraffin deposition has caused problems, specific wax dissolvers in tailored treatments have been applied during pigging programmes to aid the removal of deposits from pipe walls and to prevent further wax deposition. This paper will discuss the selection and application of these wax dissolvers and the results obtained on applying the products in field.

The laboratory methods used to evaluate and select a wax dissolver and the process of modifying the amount of chemical required will be discussed in this paper. The paper will also discuss the interaction of these dissolvers with specific hydrocarbon deposits. Furthermore, we will compare the characteristics of wax deposits retrieved from pigging programmes prior to and during dissolver application.

This paper will demonstrate that in certain North Sea fields the physical characteristics of pig waxes altered when dissolver was applied, allowing hydrocarbon deposits to be removed more effectively from the export pipeline and enhancing the cleaning phase of the pigging programme.

The application of wax dissolvers prior to and during export pipeline cleaning programmes, in preparation for intelligent pig runs, has proven beneficial where waxy crudes are being exported. The introduction of such chemical injection regimes has improved the removal of hydrocarbon wax deposits from export pipelines and has allowed meaningful data to be retrieved during intelligent pig runs.
A Novel Stimulation Technique for Horizontal Openhole Wells in Carbonate Reservoirs: A Case Study in Kuwait
Authors: Uddin Shahab , Liu Hai , Coston Chad , Yassin Mohamed , Al-Dhafeeri Fahad
Published: December 2007

Effective matrix acidizing in Kuwait's horizontal openhole wells is a real challenge. Reservoir heterogeneity and the length of the horizontal wells make acid placement and diversion difficult, particularly in high water-cut wells in which bottom water has broken through high permeability streaks or natural fractures. Furthermore, acid penetration is limited by the large surface area of the horizontal wellbore and is exacerbated by the relatively small injection rate imposed by the use of coiled tubing. To make matters worse, formation damage in horizontal wells is usually deep due to long exposure times.

This paper discusses the application of a new viscoelastic surfactant-based, self-diverting acid system for stimulation of more than 20 horizontal openhole wells in carbonate reservoirs in Kuwait. The application also deployed a new non-particulate material that forms a highly viscous plug when it contacts water, and degrades when mixed with oil in the formation. The new fluid system is pumped prior to the acid treatment to effectively prevent the acid from stimulating high water saturation sections.

The field results show significant improvement on post stimulation production owing to effective diversion and water production control, compared with wells in which a conventional polymer diversion technique was used in the past with no consideration of high water cut cases. The new technique has been selected as the standard stimulation practice in most horizontal openhole carbonate wells in Kuwait.
Innovative and Interactive Produced-Water Information Resource
Authors: Veil J. A. , Puder M. G. , Sullivan R. G. , Richmond P. D. , Kotek T. J.
Published: December 2007

Produced water is the largest volume waste stream generated during oil and gas production. Management of produced water can be costly. The industry can benefit from having readily available and unbiased information on produced water management options and regulatory requirements. This paper describes a new web-based Produced Water Management Information System (PWMIS) being developed by Argonne National Laboratory. PWMIS includes three functional modules:

A Technology Description Module, which provides basic information about practices that are currently employed to manage produced water. Users can click on any of the listed technologies to access separate fact sheets describing each technology and including references for additional information. A Regulatory Module, which identifies and summarizes existing state and federal regulations or guidelines on produced water management. Users can click on EPA, BLM, MMS, or on any state to be sent to pages that offer more information about each agency's requirements. A Technology Identification Module, in which users are asked to answer a series of questions. The replies to these questions lead users through a decision tree, resulting in a suggested subset of water management options that would make the most sense for a given geographical or environmental setting.

PWMIS is based on the successful Drilling Waste Management Information System website (http://web.ead.anl.gov/dwm) developed by Argonne in 2004. PWMIS is expected to be available to users by mid-2007.
Cementing Considerations for Casing While Drilling: Case History
Authors: Strickler Robert D. , Solano Pablo
Published: December 2007

Casing while drilling (CWD) is an emerging technology being introduced in different areas around the world This new configuration, where the casing is used as a drillstring, presents new challenges for primary casing cementing operations compared to the conventional cementing operations.

A full understanding of the required changes of the cementing methodology from conventional drillpipe drilling operations can contribute to the success of any CWD campaign. CWD cementing differs from conventional cementing practices because it is impossible to use standard centralizers attached to the casing while drilling because of extended and faster casing rotation.

When more than one bit is required to reach the next casing point, CWD requires full-bore casing access to pull and run bottomhole assemblies (BHA) through the casing. In these instances, conventional floating equipment cannot be used.

Wireline logging is normally conducted in cased hole after the cementing job. The cement volumes are calculated with a cement excess factor instead of a caliper log.

This paper describes the methodology developed to successfully cement surface, intermediate, and production casings in more than 125 wells in south Texas where CWD was used. These same techniques can be applied in CWD operations elsewhere.
Squeeze Chemical for HT Applications – Have We Discarded Promising Products by Performing Unrepresentative Thermal Aging Tests?
Authors: Wat Rex , Hauge Lars-Even , Solbakken Kåre , Wennberg Kjell Erik , Sivertsen Linda Merete , Gjersvold Berit
Published: December 2007

Selecting an effective scale inhibitor for squeeze application at 170°C is no simple task. The traditional thermal stability test by aging the chemical in bulk is often perceived to be too harsh. This results in many promising products being rejected due to their apparent degradation at temperature. The alternative of conducting aging test inside core materials, hence more representative to the downhole conditions, is NOT a novel idea. However, no definitive data is available to date that can substantiate such argument and quantify the difference between the two methods. This is mainly due to the difficulties and complexity to conduct such an experiment at high temperature over a long period of time. In this paper, the results from a recent investigation are presented. It describes the detailed procedures during the planning and execution stages, lessons learnt and pitfall to avoid. A scale inhibitor was aged using two different methods, one in bulk as commonly practiced in the industry and one inside a sandstone core. The aging period varied between 45 days as in the bulk and 110 days as for the last desorbed sample from the core. The samples which were aged inside the core retained much of their inhibition efficiency whilst that aged by the traditional method (bulk) lost nearly all its effectiveness. These results CLEARLY demonstrate that the conventional method of thermal aging in bulk is unrepresentative and that the loss in performance can be quantified. A NOVEL finding from this study is the evidences of an unexpected relationship between desorption and inhibition effectiveness. The findings from this study will have great impact on selecting chemicals for HT applications. More so in those environmental sensitive regions where the use of ‘yellow’ (biodegradable) squeeze chemicals are mandatory. Many of these have been discarded due to their apparent thermal degradation which is now proved to be unrepresentative.
Integrity Assessment of Well Barrier Threatened by Increasing Casing Hanger Loads
Authors: Okstad Eivind H. , Sangesland Sigbjørn
Published: December 2007

Degradations or interruptions of the original well barrier elements might occur at offshore wells after some time in operation. Experience from the Norwegian Continental Shelf has shown that these problems are not always treated as thoroughly as expected by the parties involved. This paper presents an approach for an efficient visualization and description of interrupted well barriers, basically to increase the well barrier control and management. By mapping the history of operational demands and load picture of the well in combination with the status of well barriers, a consistent basis for evaluations is obtained. The main intention is thus to realize the real well problem and its underlying causes in a controlled and systematic manner. Then, the responsible parties involved can take action more accurately according to the type of failure that has been revealed.
HazComWriter—Compliance Tool for MSHA Rule 30 CFR Part 47

or

OSHA Rule 29 CFR 1910.1200
Authors: Scott Douglas F. , Lecoq Paul E.
Published: December 2007

We are preparing to release a new tool to help companies write their required HazCom plan and list all hazardous chemicals at a company's site. Based in part on consumer input, we combined NIOSH's MSHA and OSHA versions of the HazCom Helper into one easy-to-use software tool. This tool, the HazComWriter, is more robust than its predecessors and features a sort utility, storage of the chemical list in an EXCEL format, and easy to use menus. The document produced by the HazComWriter will satisfy both MSHA and OSHA requirements for a "written hazardous communication document".
Optimal Waterflood Design Using the Adjoint Method
Authors: Kraaijevanger J. F. B. M. , Egberts P. J. P. , Valstar J. R. , Buurman H. W.
Published: December 2007

We address the problem how to operate the injectors and producers of an oil field so as to maximize the value of the field. Instead of agressively producing and injecting fluids at maximum rate aiming at large short term profits, we are after optimizing the total value (e.g. discounted oil volume) over the whole lifecycle of the field. An essential tool in tackling this optimization problem is the adjoint method from optimal control theory. Starting from a base case reservoir simulation run, this extremely efficient method makes it possible to compute the sensitivities of the total (lifecycle) value with respect to all (time-dependent) well control variables in one go, at a cost less than that of an extra reservoir simulation run. These sensitivities can be used in an optimization loop to iteratively improve well controls.

We implemented the adjoint method and an associated optimization algorithm in our in-house reservoir simulator. In addition to conventional well control options based on the well's pressure or total rate, we have also implemented smart well control options which allow the separate control of individual inflow intervals. Special adaptations of the optimization algorithm were required to allow the inclusion of inequality constraints on well control (pressure and rate constraints).

We applied the optimization algorithm to a number of cases, and found interesting, non-trivial solutions to some optimal waterflood design problems, that would not easily have been found otherwise.

In this paper, we also present a self-contained elementary derivation of the adjoint method, which is different from, but equivalent to the well-known derivation based on the Lagrange formalism.
ThermoChemical Process To Remove Sludge From Storage Tanks
Authors: Rocha Nelson O. , Khalil Carlos N. , Leite Lúcia C. F. , Goja Andre M.
Published: December 2007

The periodic cleaning of the bottom of crude oil storage tanks in vessels, terminals and refineries has become a big problem for industrial maintenance, principally due to the temporary inoperability of the equipment and the high environmental impact caused by the conventional treatments used. The storage of crude oil in large tanks invariably creates a gradual deposition process of organic sediments of high molecular weight.

PETROBRAS has developed a thermochemical method aimed at removing wax deposits in submersed oil pipelines, wax damage in production reservoirs and petroleum sludge removal from storage tanks.

This work presents the chemical treatment performed inside an oil storage tank located onboard an oil tanker as well as the laboratory methodology for the organic deposit physical-chemical characterization, kinetics of reaction, physical simulation, treatment dimensioning and operational treatment, aimed at the removal of 800 M3 of organic deposit.

The thermochemical method consists of a chemical reaction between two nitrogen salts that produce a strong exothermic chemical reaction. The heat produced by the reaction, together with the turbulence due to the generation of a large volume of nitrogen and the solvency, dispersed the initially solid compacted sludge at the bottom of the tank. The heat of the solution, estimated at 90°C, in contact with the sludge, irreversibly melted the organic fractions according to the previously studied phases diagram.

The method demonstrated itself to be efficient, safe and of low cost, when compared to existing classic methods. The process financial balance showed that the cost of the oil recovered from the organic deposit paid for the investment in chemical reagents and operational facilities.