Oil and gas field chemicals
AssigneeBP Chemicals Limited
InventorIan Ralph Collins
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Abstract
This invention is a process and a formulation for minimising the squeezing and shut-in operations needed to inhibit scale in a production well using the precipitation squeeze method by injecting into an oil-bearing rock formation a water-miscible formulation comprising: (a) a water-miscible surfactant which is in liquid form, (b) a solution of water-soluble metal salt comprising a multivalent cation and (c) a solution of a water-miscible scale-inhibiting compound comprising an anionic component capable of forming a scale-inhibiting precipitate in situ in the presence of the cations in (b) upon injection into the rock formation, wherein the surfactant is a glycol ether and the minimum ion concentration of the scale inhibiting compound (c) is 50 ppm based on the total weight of the formulation.
Claims34
A process for minimizing the number of squeezing and shut-in operations needed to inhibit scale and thereby increase the production rate from an oil well using the precipitation squeeze method, said process comprising injecting into an oil-bearing rock formation matrix a water-miscible formulation comprising:
- (a) a water-miscible surfactant which is a glvcol ether in liquid form,
- (b) a solution of water-soluble metal salt comprising a multivalent cation, and
- (c) a solution of a water-miscible scale-inhibiting compound comprising an anionic component capable of forming a scale inhibiting precipitation in situ in the presence of the cations in (b) upon injection into the rock formation matrix, wherein the minimum ion concentration of the scale inhibiting compound (c) is 5,000 ppm based on the total weight of the formulation, said components (a)-(c) being introduced either as a pre-formed single homogeneous composition, or simultaneously or sequentially in either order into the rock formation matrix.
A formulation comprising in an aqueous medium
- (a) at least one surfactant comprising n-butyltriglycol ether in an amount of 1-45% w/w of the total formulation,
- (b) a solution of a water-soluble metal salt comprising a multivalent cation and
- (c) a solution of a water-miscible scale-inhibiting compound in an amount of a 1-25% w/w of the total formulation and comprising an anionic component capable of forming the scale inhibiting precipitate in situ in the presence of the cations of (b) upon injection into a rock formation matrix,
- wherein the minimum ion concentration of the scale inhibiting compound (c) in said formulation is at least 5,000 ppm based on the total weight of the formulation.
Dependencies are inferred from the claim text.