Deep well cement

Time versus consistency graph of aluminum-phosphate-based deep well cement. 

Xonotlite is an important phase, because it is dominating component in the materials autoclaved at higher temperatures (Fig. 4.53), as well as formed in the pastes in deep wells cementing. 

The ASTM specifications provide for five types of Portland cements Types I, II, III, IV and V they are manufactured for use at atmospheric conditions [165]. The API Classes A, B and C correspond to ASTM Types I, II and III, respectively. The API Classes D, E, F, G, H and J are cements manufactured for use in deep wells and to be subject to a wide range of pressures and temperatures. These classes have no corresponding ASTM types. 

Examples of retarders are shown in Table 10-11. They are added to prevent cement from setting too rapidly. These additives are also referred to as set retarders. Cements with retarders to prevent rapid setting may be used at the high-temperature and high-pressure environments of deep wells. Common retarders are lignosulfonate and certain carbohydrate derivatives, such as welan gum, xanthan gum, cellulose, and polyanionic cellulose. 

The viscosity of a cement affects the pumping properties. The viscosity must be kept low enough to ensure pumpability of the slurry during the entire operation period. In deep wells, because of the increased temperature, the viscosity becomes increasingly lower, which leads to undesirable flow characteristics of the slurry. This effect can be serious, because the viscosity follows the Arrhenius law. Some of the additives used for viscosity control also... 

A cement formulation, as indicated in Table 18-6, will be useful as a plugging solution in deep and super-deep wells [34] at temperatures of 100° to 160° C and in the presence of hydrogen sulfide. The solution has a high stability against hydrogen sulfide aggression. 

When drilling deep wells, successfully filling the annulus with cement slurry can be achieved by treating the plugging slurry with plasticizers to increase its mobility. It is desirable that the plasticizer be effective in liquefying the cement slurry. Of course, it should not adversely affect other parameters of the slurry and hardened cement, and it should be readily available and inexpensive. 

P. A. Alikin, N. N. Kasatkina, N. M. Makeev, and V. Yu. Vantsev. Plugging solution for deep wells—contains slag-sand cement, iron chloride, polyacrylamide, ethyl silicate and water, and has increased isolating efficiency. Patent SU 1776761-A, 1992. 

Typical uses include the production of non-dispersible underwater concrete and reduction of the accumulation of bleed water in mass concrete placed in deep forms. Consequently, AWAs are useful in mass concrete work because they prevent the formation of laitance on the surface of the concrete and thereby reduce the excessive cleaning between successive lifts. The admixtures also reduce the voids formed under horizontal reinforcing bars. Therefore, bond to steel increases and potential corrosion problems are reduced. The admixtures are also used in conjunction with WRAs in oil-well cementing grouts to reduce pipeline friction and rapid water loss and grouting of pre- and post-tensioned concrete ducts [47]. New valves and control devices under development in Europe and Japan used in conjunction with AWA will likely advance the field on underwater concrete. 

Oil well cements must usually perform at elevated temperatures and pressures, both of which increase with increasing depth. The maximum temperature encountered at the bottom of deep wells may reach 250°C, and may even exceed 300°C in geothermal wells. Under these conditions the temperature of the sluny during pumping may reach 180°C (bottom hole static temperature). The pressure to which the cement sluny is exposed is equal to the hydrostatic load plus the pumping pressure, and may reach 150 MPa. 

Sedimentary phosphate ores, particularly those that have been subjected to the effects of heat and/or pressure (perhaps deep burial) may become highly consolidated, well cemented, and very indurated. Such phosphate ores are typically of Paleozoic or Precam-brian age. The production of well-consolidated, and highly indurated sedimentary ores may require mining and ben-eficiation techniques resembling those typically used for hard igneous phosphate ores. Such phosphate ores are mined and benefidated in India and China. 

Petroleum. Apart from its use ia petrochemicals manufacture, there are a number of small, scattered uses of lime ia petroleum (qv) production. These are ia making red lime (drilling) muds, calcium-based lubricating grease, neutralization of organic sulfur compounds and waste acid effluents, water treatment ia water flooding (secondary oil recovery), and use of lime and pozzolans for cementing very deep oil wells. 

H. Jusmes and E. Dahl-Jorgensen. Alternative cementing materials for completion of deep, hot oil-wells. Patent WO 9412445, 1994. 

Eight months after injection began in the second injection well, wastes had leaked upward into the adjacent shallow monitoring well. The leak apparently was caused by the dissolution of the cement grout around the casing. In June 1972,13 months after injection began in the second well, the waste front reached the deep monitoring well located 450 m (1500 ft) northwest of the injection well. Waste injection ended in December 1972. As of 1977, the wastes were treated in a surface facility.170... 

The various fields of chemistry play an important role in the discovery and exploitation of oil and gas reserves. Improved drilling and well completion fluids, cement slurries, hydraulic fracturing and acidizing fluids to improve well productivity, various chemical additives to be used in these fluids, and chemicals for enhanced oil recovery are essential to the improvement of production economics and to an increase in recoverable hydrocarbon reserves. Chemistry will become increasingly important in future hydrocarbon production with the decreased likelihood of major onshore discoveries, increased discovery and production costs associated with deep offshore wells and Arctic frontier provinces, and the decline in drilling since early 1982. 

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