Water-soluble polymers commonly used in the oil field are reviewed. The properties of guar, guar derivatives, cellulose derivatives, xanthan gum, locust bean gum, starches, and synthetic polymers, especially polyacrylamides, are discussed and related to chemical structures of the polymers. Original data comparing polymer solution viscosity properties under identical conditions are presented. These data include effect of polymer concentration on solution viscosity, temperature effect on solution viscosity, viscosity in acidic solution, and polymer solution viscosity in the presence of a hemicellulase enzyme.

With increased drilling of deep wells across high-pressure gas zones, the problem of gas migration in cemented gas-storage wells has become widespread. Laboratory tests and field results have helped to identify the significant role played by low fluid-loss additives in cement slurries for controlling or preventing gas migration. Introduction With deeper well completions across gas-producing horizons, especially liner cementing completions, the problems of gas leakage have become a major concern. problems of gas leakage have become a major concern. In these cases, gas leakage poses substantial problems not only in the form of potential blowouts, but also in the loss of already scarce natural resources. To determine various factors responsible for gas cutting of cement or gas leakage through a cemented annulus, model studies simulating down-hole conditions have been conducted. An examination of the published data indicates that the recommended practices for minimizing gas leakage may be classified in two categories. The first concerns methods to obtain better bonding of the cement to both pipe and formation surfaces. The pipe bonding is aided mechanically by the application of a resin-sand coating to the outer surface of the casing or liner or by removal of the mill varnish from the pipe. Most studies conducted to improve cement-to-formation bonding have evaluated techniques to increase mud displacement efficiency. These tests have indicated the importance of pipe centralization, the use of scratchers, and specially designed spacer fluids between the drilling fluid and the cementing composition. Considering all the variables evaluated during these displacement tests, the one having the most pronounced effect on increasing the mud displacement efficiency has been pipe movement. Both rotation and reciprocation have been studied. Conditioning of drilling mud to decrease plastic viscosity and yield point, together with higher displacement rates during cementing, are also an integral part of primary cementing considerations in high-pressure gas zones. The second category concerns methods that prevent entry of gas into the cemented column. Gas can only enter the cement column when the formation pressure exceeds the hydrostatic pressure at that interval; several factors that may permit reduction of hydrostatic pressure after the cement slurry is in place have been identified. Early investigations indicated that premature setting of the cement up the hole as a result of temperature anomalies or slurry dehydration, as well as gelation or increase in cement viscosity before hydration of cement, may contribute to the problem of gas migration. However, indications are that premature dehydration of cement slurry, resulting from the lack of fluid-loss control, may be the primary cause of gas communication. This problem seems most evident where permeable zones of problem seems most evident where permeable zones of varying formation pressure occur. When hydrostatic pressure exceeds the formation pressure, slurries without pressure exceeds the formation pressure, slurries without adequate fluid-loss control may undergo extensive dehydration, building filter cake across the permeable zone and resulting in bridging the annulus. The effective hydrostatic pressure will be nullified at this point and below it in the annulus. This may result in gas migration from the higher-pressure zone toward a zone of lower pressure, thus creating a gas channel in the cement column. The role played by fluid-loss additives in controlling gas leakage may be viewed from the time the slurry is placed in the annular space till the time it has finally set. placed in the annular space till the time it has finally set. JPT P. 1361

This investigation was undertaken to find the most effective material which would reduce the friction coefficient in turbulent flow when added in small quantities to oil pipelines. For this purpose, a series of oil‐soluble polymers, namely homopolymers and copolymers of alkyl methacrylates, alkyl acrylates, and alkyl styrenes were synthesized. Emulsion polymerization techniques were used. Commercially available alkyl methacrylate and alkyl acrylate monomers were used in the synthesis. Monomeric alkyl styrenes were synthesized and structures established prior to polymerization. Intrinsic viscosities were measured and viscosity average molecular weights were calculated for several of the homopolymers synthesized in this study. Reduction of factional drag and resistance to shear degradation were measured by pumping a solution of the polymer in a hydrocarbon solvent through a pipe and recording the pressure drop across the pipe. Drag‐reducing properties of several of the polymers were correlated in terms of their viscosity average molecular weights. Drag reduction of poly (isodecyl methacrylate) was studied in various hydrocarbon solvents. Drag‐reducing behavior of polymers prepared in this study exhibited a strong dependence on molecular weight; increasing the molecular weight increased the drag reduction for a given polymer concentration and pipe size. Several of these polymers were found to be superior to commercially available polyisobutylene as drag reducers, especially in terms of shear stability.

A synthetic polymer cement retarder has been designed to provide extended pumping times for cement slurries, while having minimal effect on compressive strength development. When compared to traditional lignosulfonate cement retarders, the synthetic polymer provides better response properties, and it is chemically more uniform. Deep wells with bottom-to-top temperature differentials of 150°F have been successfully cemented with slurries containing this retarder.

fax 01-972-952-9435.References at the end of the paper. AbstractGlobal economic conditions require innovative and state-of-theart wellbore-stabilization methods to reduce the total cost associated with the construction and life cycle of a well. Stabilization includes preventing unwanted fluid or gas flow into or out of the wellbore, preventing the flow of particulates into the wellbore, and mitigating formation compressive or tensile failure. Solutions should involve the use of real-time drilling data obtained from measurement-while-drilling (MWD) and logging-whiledrilling (LWD) systems, advanced fluid chemistries, computergenerated placement procedures, and job histories of similar well problems. The end result of a properly designed wellbore stability process is reduced well-construction cost. Costs are reduced by minimizing nondrilling rig time, eliminating emergency or unplanned casing strings, and reducing unwanted fluid/ gas flow that causes environmental hazards.This paper focuses on a water-dispersible, aliphatic epoxyresin system (WDR) that has been developed to plug fractures/ vugs, reduce formation permeability, and artificially increase formation fracture gradients. Aliphatic epoxy resins impart water compatibility, which is an advantage over more commonly used aromatic epoxy resins that cannot tolerate water contamination. The aliphatic epoxy-resin system can be used during drilling and can be pumped as a neat resin, resin/sand or resin/ barite mixture, or dispersed in water-or oil-based drilling fluids. A pill can be spotted over trouble zones followed by a pressure squeeze that forces resin through the mud filter cake, where it then hardens and consolidates the formation. This paper presents data that illustrate the systems capability to reduce permeability, dramatically enhance mechanical properties of the forma-tion, and solve various production-related wellbore stability problems such as annular casing pressure, water production, and multilateral junction sealing.