A Metal-Plating Process for Sand Consolidation
Authors: Strickland W.T. , Richardson E.A. , Hamby T.W. , Torrest R.S. 
Published: December 2007

Introduction

In wells producing from unconsolidated formations, one of the established methods of restricting sand entry is in-situ artificial consolidation of the sand a few inches or feet around the wellbore. Organic cementing materials, such as Eposand resins, perform satisfactorily at ordinary reservoir temperatures, but at higher temperatures they are subject to thermal or hydrolytic degradation. Inorganic systems offer inherent advantages at extremely high temperatures, such as those encountered in thermal-recovery operations, and have advantages at ordinary temperatures as well.

A new inorganic method of sand consolidation using a nickel or cobalt solution that can be made to deposit spontaneously a thin metal plating on sand grain surfaces was invented by E.A. Richardson, and is covered by U.S. Patents 3,393,737 and 3,685,582, among others. The Patents 3,393,737 and 3,685,582, among others. The consolidation is affected by a continuous layer of the deposited metal around all grain contacts and over all exposed surfaces. Since the nickel film is very thin, little loss of permeability occurs. Compressive strength is equal to or greater than that obtained with plastics, and tests indicate that the high-temperature hydrolytic stability is excellent. This technique deposits metal in the formation only about 1 ft from a wellbore.

Other applications of electroless nickel plating are envisioned. For example, the natural cementation material in a formation may be protected against solution when exposed to high-temperature steam injection, or the lifetime of plastics or other artificial consolidating material may be increased by a thin coating of deposited nickel. In addition, the electrical properties of the deposits may be used in establishing good electrical contact with formation. Applications to problems other than sand control are also feasible.

In addition to these special applications, metal plating has several advantages in normal sand-consolidation plating has several advantages in normal sand-consolidation applications. It consolidates during the injection process and so it does not require a shut-in period for curing. Furthermore, there is no possibility that the fluid can drift away from the wellbore before curing. Elimination of the curing step reduces the over-all application time and can reduce substantially expenses when a costly offshore rig is required. The consolidation is strongest at the wellbore, which is the region where the hydrodynamic forces and intergranular stresses are greatest. Thus, maximum strength is available where it is most needed. Furthermore, the system is aqueous, and thus is not as easily contaminated by formation fluids as are the organic systems.

PROCESS CHEMISTRY PROCESS CHEMISTRY

The spontaneous reduction of a nickel solution to metallic nickel by hypophosphite was first observed by Wurtz in 1844. A similar reduction of cobalt was studied by Paal and Frederic in 1931. The reductions accomplished in these studies usually yielded a black powder. Electroless plating was discovered accidentally by Brenner and Reddell. plating was discovered accidentally by Brenner and Reddell. A complete description of their process and others was published in 1957. In the electroless process, reduction published in 1957. In the electroless process, reduction of the metal takes place only on a catalytic surface immersed in the solution. Since metallic nickel and cobalt themselves catalyze the reduction, the reaction is self-sustaining once it is started.

The mechanism of the reaction has been studied in some detail and is summarized below for the nickel system.(1)Deposition of Metal (H2PO2) + (catalyst) -&gt;hypophosphite(PO2) +2H (catalyst)(2)metaphosphite + (PO2) + H2) -&gt;H + (HPO3) orthophosphite

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