Characterization of the Evolution of Cementing Materials After Aging Under Severe Bottomhole Conditions
- Didier Degouy (Inst. Francais du Petrole) | Madeleine Martin (Inst. Francais du Petrole)
- Document ID
- Society of Petroleum Engineers
- SPE Drilling & Completion
- Publication Date
- March 1993
- Document Type
- Journal Paper
- 57 - 63
- 1993. Society of Petroleum Engineers
- 1.2.3 Rock properties, 5.4.6 Thermal Methods, 1.14 Casing and Cementing, 1.11 Drilling Fluids and Materials, 1.14.3 Cement Formulation (Chemistry, Properties), 5.2 Reservoir Fluid Dynamics, 2 Well Completion, 1.6 Drilling Operations, 4.3.1 Hydrates, 2.4.3 Sand/Solids Control, 5.9.2 Geothermal Resources
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This paper describes a characterization of the evolution of some cementing materials that are currently used (cements) or are potentially usable (thermosetting resins) after they have been cured and aged under high pressure and high temperature. Specially designed testing equipment to simulate downhole conditions is shown. Variations in material characteristics were studied with standard methods (compressive strength and water permeability measurements) and physical analysis methods [scanner tomography, electronic microprobe, and scanning electronic microscope (SEM)]. The results show how aging influences the relationships between local structure and composition of materials and macroscopic properties. properties. Introduction
The tightness of the casing/formation annulus is a primary safety concern for both oil and gas wells. It prevents formation fluid from channeling from one formation to another or to the surface. This tightness can be achieved if the mud is displaced completely by the cement slurry during cementing, the cementing material is impermeable after curing and hardening, and the cement bond with the casing and formation is good. Furthermore, during the life of the well, a loss of tightness may occur, requiring expensive remedial cementing jobs that often fail. The purpose of this study was to describe the performances of long-lasting cementing materials capable of withstanding severe bottomhole conditions, namely high temperature (150 to 350C) and formation water with possible high salinity. Numerous laboratory results have been published on the behavior of cements designed for high-temperature wells. Most focused on systems consisting of API Class G or H cement and silica or on API Class J cement. Eilers and Nelson discussed the effect of silica grain size for cement/silica systems. Other water/binder compositions have been investigated, such as lime/alumina/silica/water and lime/magnesia/silica/water. More recently, the conclusions of research on cements for thermal EOR wells led to recommendation of the use of high-alumina-content cements. A general rule for cement-based materials is that formulations must be selected carefully in keeping with bottomhole conditions (temperature, formation fluid. and thermal cycling). Some workers have studied the applicability of organic resins, organosiloxane-based resins, or resin/cement systems for geothermal environments. But the use of organosiloxane-based resins cannot be envisaged at present because of their high cost. Of the organic resin group, the application of a furfuryl-alcohol-based resin was proposed for a geothermal well with a static bottomhole temperature of 227C.
Curing and Aging Equipment. Specific laboratory equipment, including curing and aging cells, was designed and developed especially for preparing and aging cementing materials under actual bottomhole conditions at temperatures up to 350C, at pressures up to 50 MPa, and in the presence of brine. The cylindrical (2.5 cm in diameter and 5 cm in height) specimens used in this study were cured in metal molds set in a holder inside the cells.
Test Procedure. The evolution of cementing materials was determined periodically during aging under bottomhole conditions. The characteristics of hardened specimens of cementing material were measured after the samples were returned to atmospheric pressure and temperature. The measurements included compressive strength, R , determination; water permeability, k,,, assessment; and structural and chemical analyses of selected Class G cement/silica-based specimens after aging under different temperature conditions with an X-ray scanner, a scanning electron microscope (SEM), and an electronic microprobe.
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