sodium salt at 141 u00b0 f and a ph of 7 and has a half life of about 16 hours whereas 2 chloropropionic acid sodium salt at this temperature and ph has a half life of about 40 hours a basic material may optionally be included with the aqueous mixture of this invention the inclusion of a basic material in the fluid loss composition reacts with the earlier generated acids thus preventing them from significantly affecting the biopolymer barrier this can result in a more abrupt release of acid when the basic material is consumed and converted to salt acceptable amounts and types of fluid loss polymers are determined by methods well known in the art the performance of specific polymers and halogen substituted organic acid salts can be predicted by measuring the decline in constant shear rate viscosity as a function of time at reservoir conditions although the constant shear rate viscosity is not a direct measurement of fluid loss control capability it is reflective of the rate of degradation of the polymers it is therefore a good predictor of the time required to break the polymers and eliminate the effective fluid loss barrier the time period for which the fluid loss barrier will be required to be effective will vary considerably between applications generally in gravel packing operations at least one 34 round trip 34 time is required a round trip time is the time needed to retrieve equipment e g perforating gun from the bottom of the hole and go back to the bottom of the hole with new equipment e.