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Publication Date: 2015-Jul-17
Document File: 4 page(s) / 40K

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Jianzhao Wang

ASI Research Center, Ashland Inc., Wilmington, DE

This research disclosure relates to a new high temperature (HT) cement retarder comprising a tetrapolymer of acrylamide/2-acrylamido-2-thylpropanesulfonic acid (AMPS)/allyloxy-2 hydroxypropyl sulfonate (AHPS)/acrylic acid (AA) and an organic acid and its use in gas/oil fields such as a high temperature and high pressure cement retarder.

Polymers are used extensively in gas/oil field applications as additives for drilling, cementing, gas and oil well fracturing, and enhancing oil-recovery processes. Synthetic, organic, and inorganic polymers, cellulose ethers, guar gum and guar derivatives, and other biopolymers such as xanthan gum, diutan gum and welan gum are widely used in the gas/oil field applications.

During construction of oil and gas wells, a rotary drill is typically used to bore through subterranean formations of the earth to form a borehole. As the rotary drill bores through the earth, a drilling fluid, also known in the industry as a “mud”, or “drilling mud” is circulated through the borehole. Drilling fluids are usually pumped from the surface through the interior of a drill pipe. By continuously pumping the drilling fluids through the drill pipe, the drilling fluids can be circulated out the bottom of the drill pipe and back up to the well surface through the annular space between the wall of the well bore and the drill pipe. The hydrostatic pressure created by the column of mud in the hole prevents blowouts which would otherwise occur due to the high pressures encountered within the well. The drilling fluid is also used to help lubricate and cool the drill bit and facilitates the removal of cuttings as the borehole is drilled.

Once the well bore has been drilled, casing is lowered into the well bore. Cement slurry is then pumped into the casing and fills into the annulus space between the exterior of the casing and the borehole. The cement slurry is then allowed to set and harden to hold the casing in place. The required compressive strength is dependent on casing and hole diameter. Generally, a compressive strength of 500 psi is sufficient for any combination of hole/casing for a typical gas and oil well.

A primary function of the cementing process is to restrict fluid movement between the subterranean formations and to bond and support the casing. In addition, the cement aids in protecting the casing from corrosion, preventing blowouts by quickly sealing formations, protecting the casing from shock loads in drilling deeper wells, sealing off lost circulation or thief zones and forming a plug in a well to be abandoned.

The cement also provides zonal isolation of the subsurface formations, helps to prevent sloughing or erosion of the well bore and protects the well casing from corrosion from fluids which exist within the well. In this scenario the important factor is the final permeability of the...