Downhole Well Communications Cable

Compositions Withstanding 315° C.

[0065]The Example shows PFA / LMW PTFE compositions withstanding exposure at a temperature much greater than the 260° C. continuous use temperature of the PFA for long periods of time, by the composition retaining its original tensile modulus. The compositions increase in tensile modulus with increasing exposure time. Table 1 reports the results wherein test samples of the melt-mixed blends of PFA with LMW PTFE are exposed to no-load heating at 315° C., in a circulating air oven. This temperature is used to qualify the compositions and components made therefrom for continuous service in downhole wells wherein temperatures as high as 300° C. can be encountered.

TABLE 1Tensile Modulus-MPaPFAPFAPFAPFAPFAWeeks2 / B-202 / A-203 / A-204 / A-201 / A-30048746548448754134774854694695086500518566503551949752049449759112502529528542602

[0066]In Table 1, the “Weeks” column represents the period of time of exposure of the tensile modulus test specimens at 315° C. In t

Tensile Testing at Elevated Temperatures

[0071]While tensile testing at ambient temperature is relied upon for determining continuous use temperature, it is also desirable to know the tensile property at a high temperature.

[0072]When the PFA / LMW PTFE composition is subjected to heat aging at 315° C. for 7 days and tensile tested at 250° C., the composition still exhibits significant tensile modulus as shown in Table 3.

TABLE 3Tensile Modulus (MPa)Test Temp. - ° C.PFA 1 / A-202354025025

[0073]When the heating of the PFA 1 / A-20 composition is done at 315° C. and tested for tensile modulus at 200° C., the results reported in Table 4 are obtained.

TABLE 4Heat aging time (hr)Tensile Modulus-(MPa)0502455.8485616856

Applications of the PFA / LMW PTFE Compositions in Downhole Well Communications Cable

[0074]Examples of components in downhole well communications cable that can be made of the compositions are described above with reference to the patents mentioned. These components can be made in the manufacture of the cable by the same melt fabrication process used to form the cable components from the polymer indicated in the patents. Generally, in the case of insulation, either primary or secondary, the component will be formed by extrusion onto the cable construction already formed. For example, cable jacket is extruded onto primary insulated conductor, the primary insulation having been previously formed by extrusion onto the conductor. The same is true for fiber optic cable. The composition is extruded onto the fiber optic to serve as protective material for the optical fiber, whether this protective material is the cable jacket and / or filler material between the optical fiber and the cable ja