The aim of the work presented in this paper is to developp the best polymer usable for BaSO4 and CaCO3 scale inhibition in harsh field conditions (3 ≤ pH ≤ 6, 130 °C ≤ T°C ≤ 200°C, 2 ≤[Ca2+] ≤ 20 g/l, adsorption on the reservoir to allow injection by squeeze). The first objective was the thermal stability. It is known that sulfonated group permits to obtain it. Thus homopolymers made with different sulfonated monomers have been aged three week at 200°C and it has been checked by Infra Red measurements that their structure were not damaged by the test. Because in some cases after degradation of the polymer, the obtained oligomers can have scale inhibition behaviour but not adsorption. Then the monomers leading to the more stable polymers have been copolymerized with monomers bearing carboxylate function and their thermal stability have been checked. The second objective was the scale inhibition and the third was the neutral behaviour in contact with high levels of Ca2+. Series of copolymers have been synthesized in order to define what compositions and molecular weights were convenient to obtain the simultaneous inhibition of BaSO4 and CaCO3 scale and no precipitation when in contact with high levels of calcium ions. The last objective but not the least is the adsorption of the copolymer on the rock. This property is necessary for using the anti-scale additive in squeeze. For the polymers which answered at the first three conditions, injections in rock sample have been made to check the adsorption ability.