Forschungs- & Entwicklungsinformationsdienst der Gemeinschaft - CORDIS

Deep high temperature cementation of casings

Cementing heights of the order of 500 m above the internal casing shoe require complex operations, involving risks of premature setting of the cement (due to the duration of the operations, the length of the casing that the cement must pass through before arriving at its destination) and the high temperature at such depths. In case of failure, these operations risk to compromise, the future use of expensive wells. The use of a cement which sets as progressively as possible is therefore a first desirable condition.

Furthermore, the very high chloride content in the brines that impregnate the terrain and the need to use cements at Soultz that are capable of resisting stimulation with fluids containing hydrochloric acid make the resistance of the cement to chlorides a second desirable condition. To satisfy these two conditions, it has been decided to use once again a type of cement known as "HMR" (High Magnesium Resistant), which was already studied, then used in 1999 by SOCOMINE for the completion of well GPK2 after tests carried out simultaneously by the laboratories of the French Petroleum Institute (IFP) and the company Dowell Schlumberger. These tests, however, revealed the very great sensitivity of the "setting time" of this product to the retardant agent used and concluded that it was absolutely necessary to carry out preliminary tests on the blends of pre-mixed cements.

The basic composition of the HMR cements used can be described as follows: - 30% Portland cement + 70% blast furnace ash ¡ú HOZ cement -72 % HOZ cement +28% Fly ash HMR cement - Various additives (salt, retardant, antifoam) HMR cement therefore barely contains more than 20% Portland cement and it has a very low porosity due to the filling of the pores by the very fines particles of fly ash (which gives it the required resistance to chlorides). Cement densities may be adapted to the in situ requirement through the use of high strength glass perls. In this way the cement densities may be dropped considerably (up to 30%) still maintaining the compressive strength. However, the use of such high strength glass perls is rather cost intensive. After the two operations carried out (on GPK3 and GPK4) as part of this programme, it seems that we can confirm that this type of cement is quite adequate for the completion of wells drilled for EGS operations in media similar to the hydrothermalized granite massif at Soultz-sous-Forts. However, it is recommended that very complete tests must be carried out on site on the HMR + retardant mix as late as possible before it is used.

Reported by

G.E.I.E. Exploitation Minière de la Chaleur
Route de Soultz ē BP 38
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