A New Technique to Evaluate Matrix Acid Treatments in Carbonate Reservoirs

Abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThis paper discusses a new technique that was used to evaluate matrix acid treatment conducted on a cased water disposal well in a carbonate reservoir. The technique relies on calculation amount of corrosion products and minerals dissolved by the acid. It was used to calculate the amount of iron dissolved by the acid and the live acid present in the flowback following the pickle treatment. Chloride ion concentration was used to determine the degree of mixing between the spent acid and formation brine. The degree of mixing was then used to calculate the volume of the produced spent acid and the amount of minerals (calcite and dolomite) that were dissolved by the acid. The chemical efficiency of the acid, defined as the actual amount of calcite dissolved by the acid/the theoretical amount of calcite that the should dissolve, was finally determined.

Pore-Network Modeling of Carbonate Acidization

“…Productivity increases observed in field conditions vary widely. Al-Dahlan et al (2000) recorded a tripling of the injectivity index in a carbonate water disposal well. Mohamed et al (1999) studied over 80 water injectors in carbonate reservoirs treated with hydrochloric acid below the fracture gradient.…”

Improving Wellbore And Formation Cleaning Efficiencies With Environmental Solvents And Pickling Solutions

“…Even injector wells can suffer from deposition of suspended oil or compressor lubricants that can cover the acid soluble deposits and act as a diffusion barrier. 23 In sour gas wells, the iron sulfide scale is often oil-wet and may contain significant quantities of oil or condensate residues. 25 In many wells, there is a high probability of encountering residues of thread sealant compound, also known as pipe dope, on the inside of the tubing.…”

“…32 • It is important to increase the residence time for the acid to dissolve more corrosion products. 23 • Iron control chemicals are not required in the pickle acid. 24 However, if the potential exists that the pickle acid could be lost to formation, then full additives, including iron control should be included.…”

Field Application of Emulsified Acid-Based System to Stimulate Deep, Sour Gas Reservoirs in Saudi Arabia

“…29,30 To assess the performance of the acid fracture treatments, samples of well flow back were collected following each major step. The concentrations of key ions were measured.…”