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Qualification of Acid Systems for Wellbore Damage Removal: Case Histories from the Norwegian Continental Shelf

Concerning acid qualification programs: • Case 1: API(1) 5CT grade 13% Cr-80 and UNS(2) S41426 martensitic stainless steel well construction materials and a reservoir temperature of 135°C • Case 2: API 5CT grade 13% Cr-80 tubing material and a reservoir temperature below 100°C

Product Number: 51317--9186-SG
ISBN: 9186 2017 CP
Author: Yogesh Choudhary
Publication Date: 2017
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$20.00
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Acid systems are commonly used to improve productivity through either near-wellbore damage removal or through dissolving scale accumulation inside the wellbore during production. This paper describes a methodology for qualification of the acid system’s material compatibility adopted by an operator on the Norwegian continental shelf.As part of the acid treatment qualification corrosion is a key parameter that should be addressed carefully particularly for high-temperature wells. This paper discusses two acid qualification programs:

  • Case 1: API 5CT grade 13% Cr-80 and UNS S41426 martensitic stainless steel well construction materials and a reservoir temperature of 135°C
  • Case 2: API 5CT grade 13% Cr-80 tubing material and a reservoir temperature of 98°C

For Case 1 the challenge was to qualify an acid system while for Case 2 the objective was to optimize the acid formula.Static corrosion tests were conducted; general corrosion rates were determined by weight loss measurements while microscopic analysis was performed to evaluate the presence of localized corrosion.This paper discusses the prejob analysis including well temperature simulation the acid recipe compositions and results from the corrosion test programs. The execution plan of the treatment pump chart and post-treatment results for Case 1 are described.The qualification approach presented describes a stringent methodology for qualification of acid systems used for scale removal or acid stimulation treatments to help prevent severe corrosion of the well construction materials.

Key words: Acid treatment, Corrosion, API 5CT grade 13% Cr-80, UNS S41426 martensitic stainless steel

Acid systems are commonly used to improve productivity through either near-wellbore damage removal or through dissolving scale accumulation inside the wellbore during production. This paper describes a methodology for qualification of the acid system’s material compatibility adopted by an operator on the Norwegian continental shelf.As part of the acid treatment qualification corrosion is a key parameter that should be addressed carefully particularly for high-temperature wells. This paper discusses two acid qualification programs:

  • Case 1: API 5CT grade 13% Cr-80 and UNS S41426 martensitic stainless steel well construction materials and a reservoir temperature of 135°C
  • Case 2: API 5CT grade 13% Cr-80 tubing material and a reservoir temperature of 98°C

For Case 1 the challenge was to qualify an acid system while for Case 2 the objective was to optimize the acid formula.Static corrosion tests were conducted; general corrosion rates were determined by weight loss measurements while microscopic analysis was performed to evaluate the presence of localized corrosion.This paper discusses the prejob analysis including well temperature simulation the acid recipe compositions and results from the corrosion test programs. The execution plan of the treatment pump chart and post-treatment results for Case 1 are described.The qualification approach presented describes a stringent methodology for qualification of acid systems used for scale removal or acid stimulation treatments to help prevent severe corrosion of the well construction materials.

Key words: Acid treatment, Corrosion, API 5CT grade 13% Cr-80, UNS S41426 martensitic stainless steel

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