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Summary. The suitability of a synthetic copolymer for drilling deep, hot wells was demonstrated through laboratory and field testing. The polymer provided fluid-loss control at 400F [204C] to clay-free saturated-salt laboratory muds and to low-solids, nondispersed field muds contaminated with drill solids and sodium and calcium salts. High-temperature/high-pressure (HTHP) filtrate was kept at less than or equal to 15 cm3/30 min after 400F [204C] heat-aging of a 19-lbm/gal [2277-kg/m3) saturated-salt mud. Weighted >18-lbm/gal [ >2157-kg/m3) potassium muds treated with the polymer showed heat stability and solids and green-cement tolerance. The polymer was successfully field-tested in two offshore wells where bottomhole temperatures (BHT's) reached 400F [204C] and salt and calcium chloride flows were encountered. Introduction Drilling deep, hot wells with water-based fluids has been limited by lack of additives that would maintain stable rheologies and fluid-loss properties at elevated temperatures. The problem is accelerated when high chemical contaminants are encountered-e.g., salts of sodium, calcium, and magnesium. The number of wells drilled with BHT's higher than 400F [204C] is relatively small, but it is expected that in conquering the unknown frontiers, the occurrence of deep, hot wells drilled through salt beds and other hostile formations will increase, Mobile Bay, AL, is one of the areas that currently is taxing drilling technology to the limit. This investigation was undertaken with the objective of extending the utility of water-based fluids to depths where temperatures higher than 400F [204C] occur and where formations release deleterious chemical contaminants. A synthetic sulfonated copolymer is discussed that provides the dual functions of rheological stabilization and fluid-loss control under such unfavorable conditions. Considerations for Filtration Control in Drilling Fluids Statistically, the mud bill is a minor fraction of the total cost of drilling a well. The drilling fluid, however, is not a minor factor in successfully making the desired hole in the ground. Success is equated to economics, efficiency, and safety in completing the drilling project. The drilling fluid can be as simple and cheap as field water viscositied by mud-making shales. As the search for hydrocarbons goes deeper into the earth and to the bottom of the ocean, however, the conditions in the well-bore get drastically transformed. Elevated temperature gradients and hostile environments are encountered. The composition and maintenance of the mud system correspondingly becomes complicated. Sustenance of suitable drilling-fluid rheologies and filtration characteristics is necessary to maintain efficiency of the drilling process. Drilling fluids are designed to suit the wellbore conditions-e.g., permeability, chemical composition of the formation. and temperature. The conditions constantly change with depth, dictating continuous monitoring of mud properties. A well-known phenomenon in chemical kinetics is the doubling of speed or rate of a chemical reaction with every 18F [10C] increase in temperature. In water-based drilling-fluid systems, components that are relatively inert to each other under surface conditions become highly reactive as temperature rises. For example, bentonitic clays, commonly used to impart viscosity and filtration-control properties, form stable systems in the presence of large concentrations of hydroxyl ions (most mud systems are highly alkaline). At temperatures higher than 200F [94C], the hydroxyl-ion/clay interaction occurs at rates sufficient to change the rheological behavior of the fluid. During the circulation downhole and back to the surface, the mud picks up contaminants (extraneous materials not present when the fluid was originally formulated). Drill solids, cement, and salts are common contaminants. At low temperatures, the mud may be able to tolerate the contaminants, but at elevated temperatures, remedial measures are often necessary. Rogers categorized high temperature as a mud contaminant. The basic difference between high temperature and the other mud contaminants-e.g., salt, cement, and drill solids-is that temperature cannot be treated out. The drilling fluid must be conditioned to perform in its presence. In water-based drilling fluids, filtration control is a closely monitored mud characteristic. Numerous problems have been associated with excessive invasion of aqueous filtrate into permeable formations. SPEDE P. 209^
Abstract The application of Bingham's law to the behavior of drilling fluids in arotational viscometer permits the expression of viscometric data in terms ofplastic viscosity and yield value, the flow properties of a plastic fluid. Acommercially available rotational viscometer is described, and when modified toa multispeed type viscometer, is shown to provide a simple and convenientinstrument for the measurement of these properties both in the laboratory andin the field. The data obtained are shown to be useful in defining andunderstanding mud control problems relating to chemical treatment and to thehydrodynamic behavior of muds. Introduction The highly complex drilling fluids which are required for deep drillingoften give rise to new and unusual mud control problems. Rapid and economicsolutions to these problems may require, on the one hand, better understandingof the changes which contaminants and chemical treating agents produce in thecolloidal and inert solids of the mud, or, on the other hand, closer control ofthe hydrodynamic behavior of the mud. The latter objective obviously can beachieved only if a correct rheological analysis of the flow behavior ofdrilling muds is available and if this is accompanied by the appropriaterheological measurements. The purpose of this paper is to describe suchmeasurements in the field, and to show how the resulting data can be of valuein solving difficult mud control problems. It is now generally recognized that Bingham's law of plastic flow can beutilized in describing the hydrodynamic behavior of drilling fluids in thenon-turbulent flow range. Beck, Nuss, and Dunn have recently applied this lawto the flow of mud in small pipes, and Rogers has reviewed the rather extensiveliterature on this subject. So far, however, the use of Bingham's law has beenrestricted to the analysis of mud flow in pipes or capillary tubes, and it hasnot been directly applied to the flow in rotational viscometers. In the work tobe reported, the Reiner-Riwlin equation for the flow of a plastic fluid in arotational viscometer has been utilized to permit the expression of multispeedviscometric data in terms of plastic viscosity and yield value, the twoabsolute flow properties of a plastic fluid. T.P. 3061
Abstract Drilling mud rheological and gel property changes due to elevated temperatures frequently cause problems in drilling deep wells. A laboratory investigation of the effects of time, temperatures up to 300F and mud composition on these properties was made with concentric-cylinder, rotational viscometers of the Fann type. The viscometers were sealed from the atmosphere to prevent dehydration of the sample. Gel strengths were found to be more sensitive than viscosities to changes in temperature and mud composition. The high-temperature gel strengths of bentonitic clay drilling fluids were not predictable from low-temperature measurements. At high temperatures, the clay flocculates. The flocculation temperature depends on the concentration and type of solids in the mud and the degree of chemical deflocculation. As the bentonite content of a mud increases, flocculation temperature decreases. Lignosulfonate treatment raises the flocculation temperature. To minimize adverse high-temperature effects on mud properties, the mud should be maintained at minimum solids content, properly treated with a deflocculant which is stable at the maximum temperature encountered and maintained at a pH high enough to insure activation of the deflocculant for the duration required. The Methylene Blue Test for cation exchange capacity of a clay was found to be a useful guide in determining when a mud contains a dangerously high clay content. Introduction In drilling a well it is desirable, for several reasons. to know the effects of time and temperature on the rheological and gel properties of the drilling fluid in the hole. Problems associated with drilling fluids normally occur down-hole, so it is reasonable to be interested in the properties of drilling fluids at the conditions which exist down-hole. It has long been observed that high pump pressures are often needed to start circulation after a trip and that the "bottom-up" mud that is circulated back to the surface is usually more viscous than it was before "cooking" at the bottom of the hole for several hours. Burkhardt showed that a knowledge of rheological properties of muds under down-hole conditions is necessary to predict pressure surges. He showed that the viscosity of a mud greatly influences the magnitude of pressure surges and the likelihood of lost returns. McLean et al. showed that the rheological properties of a mud under downhole conditions are very important to cementing operations. This paper presents data showing the effects of time and temperature on rheological and gel properties of water-base drilling fluids. Measurements of gel strengths and rheological properties were made with two different concentric-cylinder rotational viscometers of the Fann type. One was the conventional six-speed viscometer modified to operate at temperatures up to 350F and at the vapor pressure of the liquid at test temperature. The other viscometer was newly designed to operate at temperatures up to 500F and pressures up to 1,000 psi. Tests with both instruments were made under essentially the same operating conditions. The new viscometer is shown in Fig. 1. JPT P. 1074ˆ
ABSTRACT ABSTRACT Usage of the low-solids non-dispersed mud system is the main reason why drilling performance has improved considerably in Western Canadian operations during the past 2 years. The objective of this mud system is to keep total clay solids at 4 percent or less by utilizing a selectively flocculating, dual-action polymer which combines the drilled solids into flocs and also beneficiates bentonite. The drilled solids flocs are settled out in the surface circulation system and then removed from the mud system to the sump. Flow properties and water loss are controlled without resorting to chemical dispersion. The flexibility of this low-solids mud system is such that hole stability and cutting removal can be achieved without sacrificing penetration rate. Starting from this firm drilling-mud base, a combined approach can then be made which will unite other factors affecting penetration into a comprehensive program aimed at obtaining the lowest cost per foot of hole. The low-solids non-dispersed mud system must be maintained and the hole cleaned and stabilized before other drilling variables can be considered. Thus this system is the basis for an approach to improving drilling operations and should be handled properly or the entire program becomes ineffective. It becomes apparent, then, that operators must become efficient in handling the low-solids non-dispersed mud system. Some preconceived ideas about mud handling will have to be modified and adapted to obtain the proper mud system. In line with the need to modify existing circulation systems, attention should also be given to developing new systems which are better-designed to remove drilled solids. In general, drilling cost has been reduced by as much as 25 percent under that obtained using conventional mud systems and drilling techniques previously in use. At present about 70 percent of the rigs operating in Western Canada are using the low-solids non-dispersed mud system. INTRODUCTION During the past two years there has been accelerated interest in techniques used to improve penetration rates in Canadian drilling operations. These techniques have been oriented toward obtaining the lowest cost per foot while maintaining hole stability. This advance has been spearheaded by a new non-dispersed polymer mud system which has been described in detail by Lummus and field. The objective of this mud system is to keep total clay solids at 4 percent or less by utilizing a selectively flocculating, dual-action polymer which combines the drilled solids into flocs and also beneficiates bentonite. The drilled-solids flocs are settled out in the surface circulation system, then are removed from the mud system to the sump. Flow properties and water loss are controlled without resorting to chemical dispersion. With the advent of this mud system-modified to some extent by other additives-and with a consideration of annulus flow profile, hole stability is being obtained and the hole cleaned without sacrificing penetration rate. As a result of the increased use of the non-dispersed mud system, it has become apparent that a combined approach can now be made to unite other factors affecting penetration rate.
- Geology > Mineral (1.00)
- Geology > Rock Type > Sedimentary Rock (0.31)
- North America > Canada > Alberta > Peigan Field > Cve Peigan 7-29-7-8 Well (0.98)
- North America > Canada > British Columbia > Western Canada Sedimentary Basin > Greater Peace River High Basin > Stoddart Field (0.89)
- North America > Canada > British Columbia > Fernie Basin (0.89)
To carry out a successful drilling operation, a good Rate of penetration (ROP) plays a major role in understanding of the well prognosis and drilling drilling optimization and several attempts have been program is vital, because drilling contracts are made to obtain a mathematical model for ROP. In charged on day rates, (that is the type of contract this work, semi-analytical models for ROP were where the contractor is paid a specified amount for developed based on the original Bourgoyne and each day worked irrespective of the number of feet Young Model using real time bit records obtained drilled. It is the conventional operating arrangement from wells drilled in Niger Delta reservoirs. Simple where the operator assumes ALL risks in drilling the regression analysis was applied on the equation on well as well as consumables to the operators the parameter that contains differential pressure account. The drilling contractor and other Third Party (j 4), to obtain regression constants which were Service Providers are compensated for work done then used to generate mathematical relationship on a daily basis). A successful drilling operation between rate of penetration (ROP) and drilling fluid therefore will not just suffice in reaching target depth properties. Equations relating ROP to annular vis-à-vis controlling and mitigating all problems pressure losses, plastic viscosity for annular flow encountered while drilling but will also do same in under laminar and turbulent conditions, as well as record time without incurring additional costs to the gel strength/yield stress were developed, plots operator far in excess of his initial budget. Rate of obtained from these equations showed that penetration (ROP) is one of the major parameters penetration rate increases as annular pressure controlling the time to reach target depth, hence losses, and plastic viscosity under laminar and optimization of rate of penetration will greatly reduce turbulent flow decreases, and increases as yield drilling operations costs as the time to reach target stress increases.
- North America > United States (0.68)
- Africa > Nigeria > Niger Delta (0.24)