A method for removing scale-forming ions from oil and gas production equipment. An external aqueous phase of a liquid membrane system contacts said scale and solubilizes said scale-forming compounds. Scale forming ionic compounds are then transferred into an immiscible liquid hydrocarbonaceous membrane phase having a complexing agent for scale forming ions. Said hydrocarbonaceous membrane phase envelops droplets of an internal aqueous phase which has a stronger complexing agent for scale forming ions than is contained in said hydrocarbonaceous membrane phase. Scale forming ions are transferred from said hydrocarbonaceous membrane phase and are accumulated and concentrated in said internal aqueous phase. Films of scale are thus progressively removed from surfaces where they have deposited.
Barium sulfate scale is dissolved by contacting the scale with an aqueous solvent having a pH of about 8 to about 14, containing a chelating agent comprising a polyaminopolycarboxylic acid or salt of such an acid, and a synergist anion. The aqueous solvent containing the dissolved scale is regenerated by first acidifying the aqueous solvent sufficiently to generate free alkaline earth metal ions. The aqueous solvent is then mixed with a liquid membrane emulsion enveloped around droplets of an internal aqueous phase containing an anion that forms an insoluble precipitate with the free alkaline earth metal ions. The scale-free aqueous solvent is separated from the emulsion by gravity and recovered for reuse. In another embodiment, the internal aqueous phase may contain a chelating agent to remove the free alkaline earth metal ions by forming a stable complex with the ions.
A process wherein energy generated from a high impulse device is used to jar, loosen, or dislodge scale from a wellbore, downhole production equipment, or near well formation flow channels. Such jarred, loosened, or dislodged scale allows for increased amounts of scale-forming ions to be removed. Alterwards, an emulsified liquid membrane system containing surfactants therein sufficient to remove scale-forming ions is placed in said wellbore. Said emulsified membrane system is removed when the scale-forming ions have been absorbed therein.
A liquid membrane method for removing scale deposits wherein a novel chelating composition is utilized. The composition used in the external and internal aqueous phases of said membrane comprises an aqueous solution having a pH of about 8 to about 14, and an aminocarboxylic acid or polyamine chelant. Additionally, a catalyst or synergist is used in the external phase only. Preferred chelants comprise diethylenetriamine pentaacetic acid (DTPA) or ethylenediaminetetraacetic acid (EDTA) or alkali salts thereof. Anions of organic and inorganic acids comprise the catalyst used in the external phase. Catalysts which can be used include fluoride, oxalate, persulfate, dithionate, hypochlorite, formate, thio, amino and hydroxy acetate anions. When the solution containing the composition is contacted with a surface containing a scale deposit, the deposit dissolves substantially more scale quicker than heretofore possible.
A liquid membrane method for removing scale deposits wherein a novel chelating composition is utilized. The composition used in the external and internal aqueous phases of said membrane comprises an aqueous solution having a pH of about 8 to about 14, and a polyaminopolycarboxylic acid chelant. Additionally, a catalyst or synergist is used in the external phase only. Preferred chelants comprise diethylenetriaminepentaacetic acid (DTPA) or ethylenediaminetetraacetic acid (EDTA), salts, and mixtures thereof. The catalyst used in the external phase comprises an oxalate anion. When the solution containing the composition is contacted with a surface containing a scale deposit, the deposit dissolves substantially more scale quicker then heretofore possible.
The invention provides for the use of compositions to dissolve sulfate scales from surfaces containing these scales, comprising an aqueous solution of an aminopolycarboxylic acid (APCA) containing 1 to 4 amino groups, e.g., diethylenetriaminepentaacetic acid (DTPA) or ethylenediaminetetraacetic acid (EDTA), or a salt thereof, and a second component which is diethylenetriaminepenta (methylenephosphonic acid) (DTPMP) or a salt thereof, or aminotri(methylenephosphonic acid) (ATMP), or a salt thereof. More particularly, the invention encompasses a method of removing sulfate scales from surfaces on which they have formed utilizing the foregoing solutions, particularly the removal of scales from equipment and wellbore surfaces associated with the operation of crude oil and gas wells.
