bluuebunny/crossref_metadata_2025_split huggingface dataset:
Efficient Sand Cleanouts in Larger Wellbores Using Coiled Tubing: A New Approach Making an Old Problem Simple
Authors: Ovesen Monica , Sach Manfred , Laun Lyle , Gill Gregory E. , Henning Juel 
Published: December 2007

Abstract
Sand cleanouts using Coiled Tubing (CT) have been performed for as long as CT has been in service and still account for a large percentage of applications today. For larger, deviated wellbores, sand cleanouts become increasingly difficult, even with larger sizes of CT. Sand settling to the low side of the wellbore results in the formation of solids beds. In combination with the eccentric annular flow path created with the CT, substantial amounts of sand can easily be left behind. Current approaches to eliminate the solids bed involve using higher flow rates, or exotic and costly fluids, neither of which ensures complete solids removal in every case. These methods also typically spend a great deal of time circulating, after having reached the desired cleanout depth.
Using a specially developed cleanout tool and a computer simulator for solids transport provides an opportunity to optimize the operation for the removal of solids to near 100% efficiency, with all fluidizable solids being removed. Simplified operational procedures allow for making a more qualitative decision about the cleanout efficiency. This new, patented process is called "Tornado™".
In this paper, results from two case histories performed on subsea wells in the Norwegian sector of the North Sea are presented. Both operations were performed from semi-submersible rigs, with one representing the first use of 60.325 mm (2 3/8") CT from a floating platform in the Norwegian sector of the North Sea.
The process of removing the majority of sand from the wellbore with only one wiper trip will be explained, as well as a comparison of sand removal predictions from the computer simulator to actual conditions observed.
To-date, 3 cleanouts utilizing CT and the Tornado cleanout process have been performed inside 177.8 mm (7") and 244.5 mm (9 5/8") wellbores in the Norwegian sector of the North Sea. No indications of increased CT pickup weights or stuck CT were experienced while following the job program and established best practice guidelines for sand cleanouts. This indicates the Tornado cleanout tool’s reverse jetting action and circulating procedure does not increase the risk of stuck CT, while offering the advantages of a slick bottom hole assembly in larger, deviated wellbores. Centralizers are sometimes used to assist the cleanout process by disturbing the velocity profile around the bottom hole assembly. However, they also increase the risk of stuck CT and should be avoided.
Reducing the Cost of Coiled Tubing Cleanouts by Conducting Them Without Nitrogen
Authors: Portman Lance 
Published: December 2007

Abstract
One of the most common applications of coiled tubing is the removal of sand or other debris from wells. The typical operation involves circulating fluids down the coiled tubing and up the well. The fluids are designed to carry the sand from the bottom of the well to surface, without killing or over pressurizing the well.
Because most sand producing wells are under pressurized, gas is typically required to keep the hydrostatic weight of the return fluid column under that which the reservoir can support. This gas is typically nitrogen. Difficulties arise in many locations around the world where the supply of nitrogen is problematic, or at least very expensive. A cleanout method that does not require nitrogen removes the need for a timely, reliable and cheap source of nitrogen as well as the need for cryogenic pumps and tanks.
This paper details the use of concentric coiled tubing and a down hole jet pump to conduct cleanouts in the balanced or underbalanced condition without the use of nitrogen. This technique has been the subject of previous papers, demonstrating its applicability in difficult, deviated well profiles. This paper describes the enhancements made to the system to make it suitable to simple wells, focusing on low-cost, lower-tech operations as opposed to difficult applications. The first case histories are included.
Portfolio Optimization: Living Up to Expectations?
Authors: Campbell John M. , Bratvold Reidar B. , Begg Steve H. 
Published: December 2007

Abstract
This paper addresses some of our experiences in working with practitioners dealing with the adoption and implementation of formal risk and portfolio decision methods. The emergence of project investment case histories based on formal Decision and Risk Assessment (D&RA) methods provides a mixed bag of results. Though generally better than historical deterministic methods, the failures are just as illuminating as the successes. In our analysis of the case histories, we find that some of the failures can be attributed to several simplifications formalized in the process. In this paper we explore the impacts of three areas of simplification that, whilst wellintentioned, have potential to cause adverse initial reactions by professionals and management.
The first simplification covers the handling of the quality and validity of the input data used to generate the output metrics ultimately forming the foundation of the portfolio decisions. We show that ignoring intra-asset dependencies, or worse, using a P10,P50, P90 characterization derived from a base case plus an upside and downside (or even just guestimates) significantly distorts the real NPV distributions.
The second area arises from simplifying or ignoring the dependencies (or correlations) between the various assets. These inter-asset dependencies may be regional, fiscal, financial, global, technical, or life-cycle, to name but a few.
The final area of simplification is in optimizing against the expected value of the portfolio. The issue here is that there really is a distribution of possible returns for any given level of risk. If there are binding constraints then there is a substantial probability that the expected return will not be achieved. (This is analogous to the arguments that insist we need to look at the full distribution of NPV for an individual asset, not just its expected value). This problem can be overcome by applying stochastic optimization techniques.
Using a typical suite of assets that a company might select a portfolio from, we demonstrate that these simplifications cause some very real and, economically, very significant concerns. They result in selection of a sub-optimal set of assets and participation levels, which potentially leads to a different portfolio risk profile and lower returns than expected.
Production Based Probabilistic Economics for Unconventional Gas
Authors: Seidle John P. , O'Connor Leslie S. 
Published: December 2007

Abstract
Unconventional gas plays are often risky. To help understand the uncertainty inherent in these plays, probabilistic estimated ultimate recoveries (EUR's) can be employed. Once sufficient production data are available for a given play, production based probabilistic EUR's can be constructed.
Meaningful economics require introduction of a time component to such probabilistic EUR's. This study does so in two ways. First, detailed production data are used to construct probabilistic distributions for annual gas volumes. Secondly, probabilistic gas price distributions are constructed from pertinent histories. Distributions of gas volumes and prices are then coupled in Monte Carlo simulations to generate probabilistic economics. Examples are presented using production data from Raton coal gas and the Whiskey Buttes (Frontier Formation, low permeability gas field) in conjunction with Henry Hub and CIG price distributions.
Measuring Sustainable Economic Development Indicators with Fuzzy Sets: The Sustainable Development Index
Authors: Agbon I. S. 
Published: December 2007

Abstract
Sustainable economic development means different things to different stakeholders. It encompasses economic, social, political and environmental issues. Therefore, it is very difficult to measure and monitor. There has been marginal success in developing indicators that capture sustainable economic development from the perspective of the host community.
This paper develops a Sustainable Development Index (SDI) that captures the social, economic, political and environmental impact of oil and gas activities on the host community. Using a fuzzy logic model, fuzzified host community dimension indices are developed for indicators such as Life, Education, Economics, Environment, Political Participation, Social Participation (access to jobs, water, electricity, telephones, internet etc), and Gender Equality. The fuzzified outputs are then aggregated and defuzzified into a Sustainable Development Index for the host community. Using the above method, the annual SDI of a host community can be measured over the project lifetime. For a given year, the SDI of different host communities can also be measured and compared.
The paper concludes that a Sustainable Development Impact Assessment (SDIA) study should be carried out before beginning any oil and gas project. This study should be done in addition to the Environmental Impact Assessment (EIA) study. The SDIA study would establish a baseline SDI for the host community and enable oil and gas companies to monitor the sustainable economic development of the host community during the project lifetime. Oil and gas projects that do not increase the SDI of the host community during their life cycle should be rejected.
Acid Fracturing of Power Water Injectors: A New Field Application Using Polymer-free Fluids
Authors: Al-Muhareb Mohamed A. , Nasr-El-Din Hisham A. , Samuel Elsamma , Marcinew Richard P. , Samuel Mathew 
Published: December 2007

Abstract
Seawater injection has been used to maintain the reservoir pressure in a carbonate reservoir in Saudi Arabia. However, the injectivity of some vertical wells in this field is limited due to low reservoir permeability (less than 20 md). Conventional matrix acid treatments did improve the injectivity to varying degree. However, to achieve the required injection rate, some of water injectors need to be stimulated by acid fracturing.
Various acid systems have been evaluated to acid fracture injection wells. A thorough literature survey and lab testing eliminated acid systems that utilize acid-soluble polymers (both linear and cross-linked). This is mainly due to the formation damage associated with polymers, and also these systems required back-flow of the treated wells for cleanup.
To eliminate formation damage due to polymers, flowback for cleanup, and to enhance well performance, a polymer-free viscoelastic surfactant fluid was utilized in acid fracturing treatments. The fluid system includes the non-damaging viscous pad and polymer-free leak-off controlled acids. The treatment was successfully applied in the field. Cleanup by flow back was eliminated with resulting in significant increases in well injectivity comparable to horizontal wells drilled in the same area.
Effective Stimulation of Multilateral Completions in the James Lime Formation Achieved by Controlled Individual Placement of Numerous Hydraulic Fractures
Authors: Surjaatmadja Jim B. , McDaniel B. W. , Clint Brian , East Loyd E. , Schoolfield Clint , Herbel Stephen R. 
Published: December 2007

Abstract
Fracture stimulation of long openhole horizontal wells is known to be extremely difficult when conventional stimulation methods are used. The level of difficulty increases significantly when multiple fractures are to be placed in openhole multilateral wells. A relatively new hydrajetfracturing process may be one of only a few methods that can be used to fracture-stimulate multilateral wells effectively without the use of sealing devices. This process is unique because many fractures can be placed at precise locations as desired. After reviewing the recent effectiveness of the process in single-wellbore openhole completions, an operating company elected to evaluate this stimulation method for multilateral wells.
This paper describes implementation of this new technology in three multilateral wells drilled through the James Lime formation in the east Texas/west Louisiana area. Past experiences of fracture acidizing James Lime wells with hydrochloric acid (HCl) indicate that this process can be successful as a stimulation process. However, the effectiveness of fracturing these types of wells with sand or proppants was not proven. The three wells were treated using three fracture-stimulation approaches: (1) multistage combining two stages each of HCl acid and proppantfracturing stimulation, (2) multistage with only a single acid stage, and (3) proppant-fracturing stimulation alone. Well production responses resulting from these three approaches are evaluated in this paper.
New Environmentally Friendly Surfactant Enhances Well Cleanup
Authors: Hinkel Jerald J. , Brown J. Ernest , Gadiyar Bala R. , Beyer Eric 
Published: December 2007

Abstract
Saturation changes resulting from leakoff during stimulation treatments reduce the relative permeability to hydrocarbons in the invaded zone. Historically, surfactants have been added to stimulation fluids to lower the surface tension of the fluid in order to facilitate cleanup and mitigate formation damage caused by the filtrate, and this approach has become dogma. This paper, while recognizing the importance of low surface tension, focuses primarily on enhancing cleanup by altering wettability. Few studies have been performed to investigate the impact on cleanup resulting from use of surfactants to change formation wettability.
A rapid screening test has been devised to measure the effect that various additives, when added to aqueous fluids, will have on a synthetic core. The effect is determined by measuring the rate at which the fluid, with and without additives, is imbibed into a synthetic core. This rapid screening test has proven to be quite effective, in that it is simple, quick, inexpensive, and, above all, accurate. A further advantage of this method is that it provides a simple method to estimate contact angles and, therefore, provides a good measure of wettability. The simple imbibition test method has been validated by comparing the results from these tests with the results from sophisticated coreflow experiments. Results were further confirmed by greater than 40 successful treatments in the field.
In addition to cleanup performance, the research presented here focused on the environmental impact of the stimulation fluid. The ultimate outcome of the project was a stimulation fluid that performs in a superior fashion while meeting US Environmental Protection Agency (EPA) environmental requirements for offshore discharge in the Gulf of Mexico.
New Findings on Damage Potential, Geochemical Reaction Mechanisms, and Production Enhancement Applications for Citric Acid
Authors: Al-Khaldi M. H. , Nasr-El-Din H. A. , Blauch M. E. , Funkhouser G. P. 
Published: December 2007

Abstract
Application of citric acid for damage removal in both clastic and carbonate rocks has historically not received widespread acceptance due to formation damage concerns regarding precipitation of calcium citrate. In addition, usage of citric acid in place of hydrochloric acid has been avoided due to lower bulk carbonate dissolving power relative to hydrochloric acid. However, environmental, safety, and corrosion concerns with using hydrochloric acid have sparked renewed interest in citric acid for stimulation.
This paper reconsiders the use of citric acid as both an additive to conventional hydrochloric acid systems and as a stand-alone acidizing fluid. The paper reviews extensive laboratory work focused on understanding reaction pathways and geochemical precipitation issues, and takes a new look at paradigms related to the calcium citrate issue.
Laboratory studies performed independently by two research laboratories address two main areas of investigation: (1) Evaluation of potential geochemical reaction paths and precipitation of calcium citrate and (2) mechanisms for generation of differential etching in two carbonate rock lithotypes. The described mechanism for etching enhances conductivity in a contrasting mode compared to hydrochloric acid.
Findings based on this work provide new insights into the applications, usage and potential limitations of citric acid. A newly proposed process for downhole reaction is presented. This process differs greatly from long-held paradigms built on a foundation of bench-top experimentation. Factors controlling downhole reactions are disclosed and the results of core testing and fracture conductivity are presented.
A New Comprehensive Hydraulic Fracturing Technology to Minimize Formation Damage in Low Permeability Reservoirs
Authors: Jiang Tingxue , Wang Xugang , Shan Wenwen , Wang Yongli 
Published: December 2007

Abstract
In low permeability reservoirs, hydraulic fracturing treatments are usually utilized to evaluate reserve quality in exploration wells or make producing wells economically. As we all know that the formation damage during a hydraulic fracturing job may reduce a well's production rate in a large degree, so, a new comprehensive hydraulic fracturing technology aiming to minimize formation damage is put forward in the paper. Compared with the past common hydraulic fracturing technology, it mainly contains 7 sections:1)the optimization of PAD volume;2)the optimization of polymer concentration used in fracturing fluid;3)the technology of high sand concentration and the optimized proppant pumping schedule(more than 10 stages) correspondingly;4)the optimization of pumping rate and increasing pumping rate step by step during last stages of proppant pumping;5)fracturing fluid additives selection and the optimization of breaker schedule;6)forced closure technique is performed at the moment of shut-in;7)the control of bottomhole flowing pressure during flow back of fracturing fluid and production stage in the case of stress sensitivity which is usually a main characteristic of low permeability reservoirs. After the study, four exploration wells belonged to a certain oil field of petrochina are hydraulically fractured using above technology system. The well A1 and A2 get an idea post-fracturing rate of 9.12m3/d and 11.44m3/d respectively, compared with 1.94 m3/d of their adjacent well A7. what's more, a new geology reserve has been determined up to 5,000,000 tons as a result of above 2 successfully fracturing treatment wells. Similarly, the well A5 get a rate of 16.82 m3/d compared with 0.78 m3/d of its adjacent well A6, and the well A3 get 30.57 m3/d compared with 25.7 m3/d of its adjacent well A4. Overall, the comprehensive hydraulic fracturing technology put forward in the paper has a great significance in evaluating reserve quality, sometimes it may even be used to find an undiscovered reserve. On the other hand, it may also increase economic benefit of a producing well in low permeability reservoirs.
Media Sizing for Premium Sand Screens: Dutch Twill Weaves
Authors: Ballard Tracey , Beare Steve 
Published: December 2007

Abstract
Dutch twill weaves are a common filter medium for premium and expandable screens. This paper attempts to address the question of which weave aperture size to select for a particular sand. An extensive matrix of sand retention tests using reservoir sands has been performed to gain a better understanding of the retention and plugging performance of dutch twill weaves. Several weaves have been used with different weave aperture sizes as measured by a glass bead test. Sand retention testing is often fraught with experimental artifacts and the results are very dependent on experimental conditions. However, the general trend in the data from a number of tests shows good correlation between some aspects of the sand distribution and the retention performance. In particular the diameter of the largest sand grains for a particular sand (d1, d5 and d10) are shown to be important in determining retention performance. From this data, an aperture sizing criteria for dutch twill weave sand screens is proposed. The plugging performance of the weaves is also examined with respect to weave open area and sand uniformity.
Assessment of Total Skin Factor in Perforated Wells
Authors: Yildiz Turhan 
Published: December 2007

Abstract
In this study, we present methods to predict the total skin factor for perforated and damaged wells correctly. The non- linear interaction between individual skin components is accurately represented in the methods. We show that the total skin factor models based on the simple addition of individual skin factors due to formation damage, perforation, inclination, partial penetration etc… do not work.
Formation Damage Laboratory Testing - A Discussion of Key Parameters, Pitfalls and Potential
Authors: Byrne Michael , Patey Ian 
Published: December 2007

Abstract
Formation Damage Laboratory Testing is routinely performed to select optimum drilling, completion and other fluids prior to their deployment in wells. Major decisions which impact the productivity or injectivity of wells and fields are often based on laboratory tests. This paper aims to resolve some of the arguments and diversity in the procedures for laboratory formation damage tests and present clear evidence to support opinions expressed on the merits of particular tests. The paper is deliberately non-reservoir specific and will formalise in one document evidence, opinions and suggested test improvements.
New Mechanisms of Formation Damage: Lab Studies and Case Histories
Authors: Nasr-El-Din H. A. 
Published: December 2007

Abstract
Formation damage occurs during the lifetime of many wells. Loss of well performance due to formation damage has been the subject of several review articles. Fines migration, water, emulsion blockage, inorganic scale, asphaltene, and other organic deposition are a few mechanisms that can cause formation damage.
The present paper discusses new formation damage mechanis ms that are caused by various chemical treatments. These include: adsorption-type scale squeeze treatments (phosphonate-based inhibitor), solvent treatments (a neat mutual solvent) to remove water blockage in a tight carbonate reservoir, and regular mud acid (HCl:HF at 12:3 weight ratio) to remove drilling mud filter cake in sandstone reservoirs. These treatments were designed to remove a known form of formation damage. However, they created new forms of formation damage, which resulted in a significant decline in the performances of several wells.
Case studies of new damaging mechanisms that resulted from various chemical treatments are discussed in this paper. Details of lab and fieldwork that were performed to identify the damaging mechanisms and determine its impact on well performance were addressed. Finally, the paper highlights the remedial actions and field application that resulted in restoring the performance of various wells without affecting the integrity of the formation.