Oil well cementing process

A process for sealing at an elevated temperature a zone penetrated by a wellbore using a high efficiency non-gelling hydraulic cement composition having a high degree of predictability for controlling rheology and setting time comprising mixing an aqueous slurry of hydraulic cement with up to about 2% on a dry cement weight basis of a retarder consisting essentially of at least one water soluble hydroxy carboxylic acid and a low molecular weight sulfoalkylated lignin;

• wherein the concentration of retarder is calculated to control the setting time of said hydraulic cement to exceed the pumping time;
• wherein the weight ratio of acid to lignin is in the range of about 1:0.1-5.0;
• wherein said carboxylic acid is a substantially linear aliphatic acid having at least one terminal carboxyl group in the form of acid, salt of mixtures thereof;
• wherein said sulfoalkylated lignin has a molcular weight in the range of about 2,000-10,000 and which is substantially sulfoalkylated on the benzene ring in the lignin molecule in the position ortho to the free phenolic hydroxy group and the sulfonate group is attached to the ortho position by an alkylidene radical having one to three carbon atoms;
• pumping said hydraulic cement mixture into said zone without gelation and maintaining said hydraulic cement mixture in said zone until a high compressive strength is attained.

In a process for cementing a zone at an elevated temperature by pumping an aqueous hydraulic cement slurry into said zone, the improvement of controlling the setting time of said cement and preventing gelation of said cement by mixing with said hydraulic cement a high efficiency non-gelling retarder consisting essentially of a mixture of at least one water soluble hydroxy carboxylic acid and a low molecular weight sulfoalkylated lignin;

• wherein the concentration of retarder is calculated to control the setting time of said hydraulic cement to exceed the pumping time;
• wherein the weight ratio of said acid to lignin is in the range of about 1:0.1-5.0;
• wherein the carboxylic acid is a substantially linear aliphatic acid having at least one terminal carboxyl group in the form of acid, salt or mixtures thereof;
• wherein said sulfoalkylated lignin has a molecular weight in the range of about 2,000-10,000 and which is substantially sulfoalkylated on the benzene ring in the lignin molecule in the position ortho to the free phenolic hydroxy group and the sulfonate group is attached to the ortho position by an alkylidene radical having one to three carbon atoms.