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

An increase in the number of deep wells being drilled where extreme bottom-hole temperatures are encountered, and the anticipated drilling of wells where temperatures in the range of 500°F or higher may occur, has brought about a comprehensive investigation of cementing materials and of the techniques involved in their proper usage at these elevated temperatures.Included are developments in cements, retarders, weighting materials and other cement additives which make it possible to formulate a variety of compositions to help resolve the cementing problems of these extreme well conditions. The problems associated with the selection and testing of cements are discussed, and a resume of field results is included.Previous studies on strength retrogression indicate that caution should be exercised in the selection of a cementing composition for use in high-temperature wells. It now appears that, by the addition of silica flour as a stabilizing additive to certain cements, compositions covering a wide range of slurry densities can be designed to meet extreme well conditions without strength retrogression.Improvements in cement retarders make it possible to produce a four-hour thickening time at static temperaturres up to 500°F. This temperature is considerably higher than conditions presently being encountered in drilling and completion work. Inert weighting materials, used to produce 20-lhl gal or heavier cement slurries, are reviewed.

Cementing deep, high-temperatw-e oil wehts where static tenzperatwes range from 350 to 400F hm become routine in the past decade. [n the United States there were 271 wells drilIed deeper than 15,000 ft during 1963. Many of these wells had stotic temperatures higiter than 400F, Bottom-?tole static temperatures near 700F are now realities in the, geothermal (steam producing) wells of California's Salton Sea area, The detailed planning initiated prior to drilling the wells is discussed together with the methods, materials and equipment used in solving the cementing problems which are encountered. Data are also presented that lead to developtnent oj cementing compositions that provide adequate thickening time, do not retrogress in strength, attd maintaPz low permeability under these extreme temperalgre conditions, Field data inchtde the cementing programs used on eight relatively trouble-free geothermal steam WWS in the Salton Sea urea.

American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. This paper was prepared for the 1970 Evangeline Section Regional Meeting of the Society of Petroleum Engineers of AIME, held in Lafayette, La., Nov. 9–10, 1970. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor of the appropriate journal, provided agreement to give proper credit is made. provided agreement to give proper credit is made. Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussion may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines. Abstract A study has been made as to the effect of acidic type effluents for Deep Well disposal, on various cementing compositions as well as their effect on plastic pipe. Data will include laboratory test results on API Class A, C and H Cements, Pozzolan Cement, Resin Cement, Gypsum Cement with Resin Phase and a Resin Slurry using Sulfuric Acid, Nitric Acid, Hydrochloric Acid and Mixed Acids. A section is devoted to well design which includes optimum pipe to hole size ratios, recommendations for down hole equipment such as special packers, the use of plastic and stainless steel pipe and various techniques gained from field experience in cementing Acid Disposal Wells. Introduction It is only within the last decade that the magnitude of the damage wrought to our natural resources, surface as well as sub-surface, has become a major concern to individuals, sportsman groups, conservation, State and Federal Government Agencies. Viewpoints are many and varied as to the availability of sufficient fresh water supplies to take care of both human and industrial needs, however, the consensuses seem to be that supplies are available if they are not wasted through misuse or by pollution from industrial wastes. More stringent laws are in the making by both the State Governments and the Federal Government. Most areas are concerned with the problem of pollution in one form or another, with the more serious situations developing in industrialized and metropolitan areas. In many of these areas, water pollution as pertains to lakes, rivers and streams as well as underground fresh water supplies is a very serious problem. The primary methods used in the disposal of industrial wastes are surface and sub-surface. Many different means have been used in surface disposal operations depending upon the type of waste and the condition of the final waste at the receiving point. Generally the treatment for surface disposal is classified as chemical, physical, or biological; however, any physical, or biological; however, any combination of these three may be used. Where the final product is deposited back to an area for re-use, some of the more expensive methods of surface disposal include land fills, settling tanks, filtration systems, aeration, floatation, oxidation, chlorination, pH adjustment, etc. These are not the most effective methods of waste disposal as considerable damage can result from spillage, overflow from heavy rains, seepage, etc.

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