Research On Low Damage Contol Fluid Resisting High Temperature Of Gas Well

Abundance natural gas is available in Jilin Longshen Block. The well depth of the block to be exploited is 2700-3800m, with the bottom hole temperature of 150℃. Now the depth of LongshenⅢis 3097m, and the design depth is 4500m. The temperature tolerance of control fluid is more and more important along with the increasing of gas well depth. The control fluid applied in Jilin Oilfield shows poor temperature tolerance and huge reservoir damage. Here is a complete research on the control fluid system with high temperature resistant and low reservoir damage especially for Jilin Longshen BlockBased on the essential characteristic of Longshen Block, its sensitivity was evaluated and summarized by means of physical analysis, like bulk-rock analysis and cast-slice analysis. The design principle of control fluid was established on the bases of block sensitivity, including low filtration, dissolubility of the filter cake, strong capability of clay expand-rejection, and alkalinity. Low causticity under high temperature should be considered when it comes to the casing pipe.The temperature tolerance of high polymer molecular and the high temperature-stability of control fluid were the focuses of the study, as a result of the high temperature destruction to molecular structure of the high polymer. The control fluid system was on the basis of tackifier and fluid loss additive. The optimum formula of various densities was established according to the adjustment of treating chemical volume. Finally we got the low damage control fluid system, which was suitable at a temperature of 150℃, with the density range of 1.1-1.5 g/cm~3.The comprehensive performances of the clay-free control fluid system were measured at room temperature, including the high temperature stability, HTHP filtration property, nicer gas erosion resistance, well subside stability, low reservoir damage, and non-corrodible of CO2. Under the laboratory-construction simulating condition, the evaluations made a direction for the control fluid study and also protection for the site progress.