No abstract
The offshore drilling industry is faced with many different types of problems such as operation and logistics, weather, and actual drilling problems that hinder or halt all operations. One of the more costly drilling problems is differential pressure pipe sticking. A recent study on this problem showed that an average expenditure of more than $93,000 was required to resume drilling operations after the pipe had become stuck. If the severity of this problem can be reduced or eliminated altogether, then the total cost to the operator can be reduced and drilling can proceed more efficiently. It was the general purpose of this work to study certain aspects of drilling fluids relative to pipe sticking and if possible, to define any parameters that could be used to avoid future incidences of stuck pipe. The approaches specifically used in this study were (1) an analysis of field cases of stuck pipe in an effort to define mud systems more conducive to pipe sticking, (2) an actual field case example of how the procedures presented within the paper were used to prevent pipe sticking on an offshore platform that had previously exhibited pipe sticking problems, and (3) laboratory results obtained in an effort to further determine the effects of mud types and mud additives on differential pressure pipe sticking. INTRODUCTION Differential pressure pipe sticking is a drilling problem in which the drill string becomes embedded in a mud solids filter cake, usually across a permeable zone, and is held in place by an amount of differential pressure. Differential pressure is the difference between the drilling fluid hydrostatic pressure and the formation fluid pressure. This type of pipe sticking usually occurs after the pipe remains motionless in the wellbore for a period of time and is identified by no impedance of drilling fluid flow in the annular space and the inability to move the pipe in either vertical direction. The principal methods used for releasing stuck pipe range from a chemical approach such as spotting fluids to mechanical methods including impact loading and hydrostatic reduction. Although each is theoretically sound, the manner of practical implementation often negates the methods effectiveness. Therefore, it would seem that preventive procedures are perhaps the best approach rather than being forced to resort to remedial pipe releasing techniques. LITERATURE REVIEW Helmick and Longley2 were the first to define the differential pressure pipe sticking mechanism. They conducted laboratory investigations with several pieces of test apparatus that were capable of obtaining differential pressures across a mud cake, total filtrate through a simulated permeable section, and the required pullout force on the pipe after it became stuck. They observed that regardless of set time, the pullout force of the rod stuck in the test apparatus could always be lowered by reduction of the differential pressure. However, even when no differential pressure was applied, a significant adhesive force was often required to move the rod. It was found that 45% of the force required to free the drill pipe was required to overcome the adhesion of the mud cake to the steel.
I vividly remember that day not too distant. My office had been making a persistent and a demanding case that quick departure was prudent and necessary. Upon boarding the Boeing 747, we sat on the tarmac for an hour before the pilot advised of the delays. It seemed that Lloyd' s had reminded the airline that insurance coverage did not extend to war zones. To leave on this flight, a handsome surcharge is required to self-insure the flight. Looking out of the airplane window sitting on the tarmac in Doha, Qatar, craters caused by Saddam Hussein' s recent scud missile attacks were easily observable. The decision to self-insure seemed appropriate at the moment. The flight departed shortly thereafter and landed in London 8 hours later. The Gulf War of 1991 had started in mid-flight. As these words are crafted, I am sitting in Lillehammer, Norway, at a Lloyd' s insurance conference, and a topic of the day is war and terrorism coverage. Upon my return to Houston in a short time, the scenario may be the same as my Qatar-to-London flight only a few years ago; a war is under way, and the world again is in chaos.
Carter, D.R., and Adams, N.J., Prentice and Records Enterprises, Inc. Prentice and Records Enterprises, Inc. Copyright 1979, American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. Petroleum Engineers, Inc. This paper was presented at the 1979 Society of Petroleum Engineers of AIME Deep Drilling and Production Symposium held in Amarillo, Texas, April 1–3, 1979. The material is subject to correction by the author. Permission to copy is restricted to an abstract of not more than 300 words. Abstract When a well is to be drilled in a known or suspected sour gas area a number of precautions must be taken. These measures can be separated into the three general categories of (1) methods of protecting the rig and site personnel, (2) safeguards to protect the general public, and (3) precautions to safeguard all equipment from exposure to hydrogen sulfide. Introduction Hydrogen sulfide (H2S) has become an important topic in recent years due to the increasing demand for hydrocarbon products. To meet these demands, operators are now increasing drilling activities in known sour gas areas. In addition, sour gas has been reported in old fields where the presence of hydrogen sulfide had not been previously reported. To drill and complete a sour gas well safely and at minimum costs, operators need a basic understanding of the effects of encountering hydrogen sulfide. Hydrogen sulfide is a toxic gas that can cause sudden death from exposure to low concentrations of the substance. In addition to the toxicity, hydrogen sulfide is very corrosive. H2S corrosion adds tremendous costs to an already expensive endeavor if the operator has not taken proper precautions to prevent such damage. prevent such damage. This state-of-the-art paper presents pertinent topics relative to hydrogen sulfide drilling such as the responsibilities imposed by federal and state regulations. Emphasis is placed on OSHA and NIOSH rules and state regulations. The effects of hydrogen sulfide on the rig site worker and equipment also will be presented as well as methods for preparing and protecting workers and equipment for exposure to an H2S environment. RULES AND REGULATIONS The operator is faced with many rules, regulations, and standards when attempting to drill and produce hydrocarbon products containing hydrogen produce hydrocarbon products containing hydrogen sulfide components. The regulatory agencies are found both on the state and federal level. The primary regulations will be presented in the following primary regulations will be presented in the following section while details of these regulations can be found in the referenced sources. Occupational Safety and Health Administration (OSHA). Although a particular drilling area may be void of state regulations relative to hydrogen sulfide drilling, many federal regulations and standards must be followed anytime a toxic environment is encounterd. The Office of Occupational Safety and Health Administration (OSHA) in its 29 CFR 1910, Subpart I 1910.134 states that "(1) In the control of those occupational diseases caused by breathing air contaminated with harmful dusts, fogs, fumes, mists, gases, smokes, sprays, or vapors, the primary objective shall be to prevent atmospheric contamination. When effective engineering controls are not feasible, or while they are being installed, appropriate respirators shall be worn pursuant to the following requirements. (2) Respirators shall be provided by the employer when such equipment is necessary to protect the health of the employee. The employer shall provide the respirators which are applicable and suitable for the purpose intended. The employer shall be responsible for the establishment and maintenance of a respiratory program."In this same publication, guidelines are presented for the selection of respiratory equipment presented for the selection of respiratory equipment on the basis of exposure. The standard from which the information is obtained is ANSI Z88.2. This standard classifies H2S as an extremely toxic gas and is immediately dangerous to health. Those respirators which are acceptable must be of the positive pressure type which maintains a constant positive pressure type which maintains a constant pressure within the facepiece at all times. This pressure within the facepiece at all times. This classification is further defined by 29 CFR 11 which specifically states the types of respirators that are approved in an H2S environment. (See Table 1)American National Standards Institute (ANSI). Another national standard which has a great impact upon respiratory equipment is American National Standards Institute Z37.2-1972.
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