1,720,956 research outputs found
Prediction of Critical Pipe Running Speed During Tripping in Drilling Operations
No full textBlowout and loss of circulation are two serious accidents that can happen while drilling without the control on drillstring running speed during tripping operations. Exceeding the critical running speed during tripping-out (high swabbing pressure) and lack of control of mud rheology are the main causes for blowout. Also, exceeding the critical running speed while tripping-in (high surge pressure) and lack of control of mud rheology are the main causes for loss of circulation. Many factors which affect surge and swab pressures must be precisely selected in order to control kicks or blowouts and to prevent loss of circulation. Prediction ofthe critical pipe running-in and -out speeds during tripping operations is therefore very important. This can be done by the evaluation of several basic fluid flow equations. A computer program has been developed to simplify these ca1culations. The developed program requires fairly simple input data which can be measured in laboratory in addition to hole and drillstring dimensions. The output of this program then is transformed into graphical form from which the safe running-in and -out speeds during tripping can be predicted. As an alternative and direct way to predict the critical pipe running speed during tripping operations two correlations have been developed. These colTelations account for the govel11ing factors which affect the tripping-in and -out speeds including mud properties and drillstring and hole configuration. A comparison between the critical pipe running speed computed using the two methods has been outlined and very good accuracy based on the coefficient of linear correlation (r2) and the standard error of estimate (SEE) (r2 = 0.995 ; SEE = 0.39 for running-out correlation and r2 = 0.875 ; SEE = 0.8] 7 tor running-in correlation) have been obtained. Critical tripping speeds were found to be greatly dependent on mud weight and rheology, hole diameter and drillcollars-to-dri11pipe length ratio.Corresponding Author:
Professor Musaed N. J. Al-Awad, Petroleum and Natural Gas Engineering, Department, College of Engineering, King Saud University, PO Box 800, Riyadh 11421, Saudi Arabia
Rheology and corrosivity of drilling fluids formulated from AI-Ghatt Saudi clays
No full textAn experimental investigation has been carried out to determine the rheological and corrosive properties of AI-Ghatt clay, when used as a basic constituent for drilling fluid, on mild steel and J-55 steel alloys normally used in oil and gas wells casing fabrication. The study was extended to investigate the effect of a sodium hydroxide (NaOH) addition on the corrosive properties. Corrosion rates were measured under both static and dynamic conditions at 15% by weight clay concentration and with the addition of various concentrations of sodium hydroxide (NaOH). Under the static conditions, the maximum corrosion rate was found to vary &om zero to 73.25 mil-inch/year. Under dynamic conditions, however, a maximum corrosion rate of 155.3 mil-inch/ year and a minimum of 0.125 mil-inch/yearwas detected. The results showed that the resistance to corrosion of the steel alloys is very good at high alkalinity drilling fluids in both static and dynamic conditions. Based on the rheological and corrosivity tests, drilling fluids formulated from AI-Ghatt clay are suitable for oil and gas wells drilling as long as the concentration of the NaOH is maintained at 1% by weight
A Laboratory Study of Factors Affecting Primary Cement Sheath Strength
No full textAn investigation of factors affecting cement sheath strength has been carried out.. This study performed on hardened (cured for seven days) cement specimens. These specimens were prepared by mixing 35% fresh water by weight of dry Portland cement (class A according to API classification or C 150 type I according to ASTM classification) plus various percentages of Thumama sand (5-40% by weight of dry cement). The relationship between cement tensile and compressive strengths as well as cement direct and indirect tensile strenghs have been established. Factors affecting cement-casing and cement-formation shear bond strength were studied. Cement compressive and tensile strength were correlated to each other as well as to the cement shear bond strength. It was found that casing surface roughness, casing surface cleaning and casing centralization have enhanced the strength of cement-casing shear bond, whereas the deposition of mud cake on the wall of the simulated borehole has reduced the strength of cement-formation shear bond
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Alteration of Saudi reservoir rocks wettability due to drilling fluids contamination
No full textCorresponding Author:
Mr. Abdel-Alim H. El-Sayed
Petroleum Engineering Department, College of Engineering, King Saud University, P.O. 800, Riyadh-11421, Saudi ArabiaWettability is a key parameter that affects the petrophysical properties of reservoir rocks. Mud filtrate during the drilling of the pay zone causes a significant change in rock wettability that will affect the oil production and enhanced oil recovery methods [EOR]. This change depends on the mud filtrate and the oil rock systems involved. The objective of this paper is to investigate the influence of water base mud, oil base mud, and Partially Hydroxide Polyacrylamide (PHPA) mud filtrate on the reservoir rocks wettability. The drilling fluid formulations that recommended for drilling horizontal wells had been used in this study. The reservoir rocks used were Saudi water-wet sandstone and limestone. The contact angle was used to measure the rock wettability. Also, the effect of temperature on wettability alteration had been studied. The results showed that the rock samples used are originally water-wet. Water-based drilling fluids tend to make the system water-wet. The contact angle tends to increase with increasing NaOH and KOH additives at both 25° and 60°C. In contrast, oil-based drilling fluids change the system from water-wet to strongly oil-wet. This change is higher with crude oil than with diesel oil. PHPA mud contamination strengthen the wettability of water-wet reservoir rocks towards water. The effect of temperature increase is variable. It increases the contact angle with oil-based mud while reduces it with water-based and PAPA muds. This change is higher with limestone rock than with sandstone rock
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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