Retarded Cement Compositions and Methods for Well Completions

Abstract

Cement retarders are based on blends of lignosulfonate compounds, borate compounds and gluconate compounds. The compounds are present in certain ratios that allow the retarders to operate at temperatures and pressures up to and exceeding about 176° C. and 152 MPa. The retarders may also be provided in liquid form, improving their suitability for use at offshore well-site locations.

1 . A well-cementing composition, comprising Portland cement, water and a retarder comprising a lignosulfonate compound, a borate compound and a gluconate compound, wherein the lignosulfonate:borate-compound concentration ratio in the composition is lower than about 0.75:1, and the lignosulfonate compound, the borate compound and the gluconate compound are present in the blend at a lignosulfonate compound:borate compound:gluconate compound concentration ratio between 0.1:1.0:0.1 and 0.5:1.0:0.5 by weight,
 wherein the lignosulfonate compound is an oxylignin and the borate compound is sodium pentaborate decahydrate, sodium tetraborate decahydrate or both, and   wherein the composition further comprises AMPS-acrylamide copolymer or styrene butadiene latex.   
     
     
         2 . The composition of  claim 1 , wherein the lignosulfonate compound comprises sodium lignosulfonate, and the gluconate compound comprises sodium gluconate. 
     
     
         3 . The composition of  claim 2 , wherein the sodium lignosulfonate:sodium gluconate concentration ratio is between about 70:30 and about 30:70 by weight. 
     
     
         4 . (canceled) 
     
     
         5 . (canceled) 
     
     
         6 . The composition of  claim 1 , wherein the retarder is liquid. 
     
     
         7 - 15 . (canceled)